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Short title: Roles of cell wall-degrading enzymes in siliques 1
Corresponding authors: Ming Yang ([email protected]), Department of Plant Biology, 2
Ecology, and Evolution, Oklahoma State University, 301 Physical Sciences, Stillwater, OK 3
74078, USA; Hong Wu ([email protected]), State Key Laboratory for Conservation and 4
Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou 5
510642, China 6
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CELLULASE 6 and MANNANASE 7 affect cell differentiation and silique 8
dehiscence 9
Hanjun He,a,b* Mei Bai,a* Panpan Tong,a Yanting Hu,a Ming Yang,b,1 and Hong Wua,1 10
a State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South 11
China Agricultural University, Guangzhou 510642, China 12
b Department of Plant Biology, Ecology, and Evolution, Oklahoma State University, 301 13
Physical Sciences, Stillwater, OK 74078, USA 14
One sentence summary: Arabidopsis CEL6 and MAN7 proteins affect cell morphology and 15
silique dehiscence, which can be manipulated to different degrees by altering their activities. 16
* These authors contributed equally to this work. H.H., H.W., and M.Y. designed the 17
experiments. H.H., M.B., P.T., and Y.H. conducted the experiments. H.H., H.W., and M.Y. 18
analyzed the data. M.Y., H.H., and H.W. wrote the paper. 19
1 This work was supported by grants from the National Natural Science Foundation of China 20
(project nos.31070159 and 31470293) to H.W., funds from South China Agricultural University 21
to H.H., and grants from Oklahoma Center for the Advancement of Science and Technology 22
(PSB08-021 and PS13-006) to M.Y. 23
24
Address correspondence to [email protected] or [email protected] 25
26
The authors responsible for distribution of materials to the findings presented in this article in 27
accordance with the policy described in the Instructions for Authors (www.plantphysiol.org/) 28
are: Hong Wu ([email protected]) and Ming Yang ([email protected]). 29
Plant Physiology Preview. Published on January 18, 2018, as DOI:10.1104/pp.17.01494
Copyright 2018 by the American Society of Plant Biologists
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ABSTRACT 30
31
Cellulases, hemicellulases and pectinases play important roles in fruit development and 32
maturation. Although mutants with defects in these processes have not been reported for 33
cellulase or hemicellulase genes, the pectinases ARABIDOPSIS DEHISCENCE ZONE 34
POLYGALACTURONASE 1 (ADPG1) and ADPG2 were previously shown to be essential for 35
silique dehiscence in Arabidopsis. Here we demonstrate that the cellulase gene CELLULASE 6 36
(CEL6) and the hemicellulase gene MANNANASE 7 (MAN7) function in the development and 37
dehiscence of Arabidopsis thaliana siliques. We found that these genes were expressed in both 38
vegetative and reproductive organs, and that their expression in the silique partially depended on 39
the INDEHISCENT (IND) and ALCATRAZ (ALC) transcription factors. Cell differentiation 40
was delayed in the dehiscence zone of cel6 and man7 mutant siliques at early flower 41
development stage 17, and a comparison of the spatio-temporal patterns of CEL6 and MAN7 42
expression with the locations of delayed cell differentiation in the cel6 and man7 mutants 43
revealed that CEL6 and MAN7 likely indirectly affect the timing of cell differentiation in the 44
silique valve at this stage. CEL6 and MAN7 were also found to promote cell degeneration in the 45
separation layer in nearly mature siliques, as cells in this layer remained intact in the cel6 and 46
man7 mutants and the cel6-1 man7-3 double mutant, whereas they degenerated in the wild-type 47
control. Phenotypic studies of single, double, triple and quadruple mutants revealed that higher-48
order mutant combinations of cel6-1, man7-3, and adpg1-1 and adpg2-1 produced more severe 49
silique indehiscent phenotypes than the corresponding lower-order mutant combinations, except 50
for some combinations involving cel6-1, man7-3, and adpg2-1. Our results demonstrate that the 51
ability of the silique to dehisce can be manipulated to different degrees by altering the activities 52
of various cell wall modifying enzymes. 53
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INTRODUCTION 55
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Cellulose, hemicellulose, and pectin are common components of plant cell walls (Keegstra, 2010) 57
that need to be modified or degraded during cell differentiation and organ abscission and 58
dehiscence in plants. Cellulases, hemicellulases, and pectinases in plants are responsible for the 59
modification or degradation of the three cell wall components, respectively. Although the 60
biochemical reactions catalyzed by these enzymes are generally understood, knowledge of their 61
biological functions in developmental processes is limited. Most notably, genetic studies of a 62
combined effect of loss of function in more than one type of these enzymes on a plant 63
developmental process have not been conducted. Such studies can yield insight into how the 64
three types of enzymes together affect the same plant developmental process, which may be 65
relevant to improving agriculturally important traits of crops. For example, the kinetics of 66
ripening, abscission, and dehiscence of crop organs or seeds can conceivably be manipulated by 67
altering the activities of one or more of these enzymes. 68
Plant pectinases are responsible for degrading pectin that is mostly located in the middle 69
lamella where cell-to-cell adhesion occurs. Pectinases are expected to play a major role in cell 70
separation during abscission and dehiscence. Indeed, multiple investigations have provided 71
experimental evidence for the role of pectinases in abscission and dehiscence. The endo-72
polygalacturonase (PG, a pectinase) gene RDPG1 in Brassica napus has been found to be 73
expressed in the fruit dehiscence zone (Petersen et al., 1996). A promoter region of this gene also 74
drives expression of the β-glucuronidase (GUS) gene in abscission and dehiscence zones and the 75
style during pollen tube growth in Arabidopsis thaliana (Sander et al., 2001). Conversely, the 76
promoter of ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1), 77
an Arabidopsis homolog of RDPG1, drives expression in the anther and fruit dehiscence zones 78
and the seed abscission zone in B. napus (Jenkins et al., 1999). positional sterility 2 (ps-2), a 79
pectinase in tomato, is a homolog of ADPG1 in Arabidopsis and is required for anther 80
dehiscence (Gorguet et al., 2009). These findings suggest functional conservation of pectinases 81
in abscission and dehiscence in plants. In Arabidopsis, five PG genes have been found to be 82
expressed at locations where cell separation occurs, which include the abscission zones of floral 83
organs and the dehiscence zones in anthers and siliques (González-Carranza et al., 2007). Loss of 84
function in ADPG1 caused delayed shedding of Arabidopsis floral organs (González-Carranza et 85
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al., 2007). Ogawa et al. (2009) reported that the three closely related Arabidopsis PGs, ADPG1, 86
ADPG2, and QRT2, are involved in multiple cell separation events in reproductive organs, with 87
ADPG1 and ADPG2 being essential for silique dehiscence. Ogawa et al. (2009) also showed that 88
the expression of ADPG1 and ADPG2 in the silique dehiscence zone and the seed abscission 89
zone, and the expression of ADPG1 in these two cell separation zones depends on the 90
transcription factors INDEHISCENT (IND) and HECATE 3 (HEC3), respectively. IND is 91
known as a regulator of cell division and differentiation in the dehiscence zone in the silique, and 92
is required for silique dehiscence (Liljegren et al., 2004; Wu et al., 2006; van Gelderen et al., 93
2016). In tomato (Solanum lycopersicum), expression of genes encoding pectinases in the pedicel 94
abscission zone depends on the MADS-box transcription factors J, MC, and SIMBP21, and a 95
similar mechanism is predicted to occur in apple (Nakano et al., 2015). Parallel to their roles in 96
abscission and dehiscence, pectinases also participate in fleshy fruit ripening (García-Gago et al., 97
2009; Roongsattham et al., 2012; Fabi et al., 2014). 98
Plant cellulases degrade cellulose, which is a major component of the cell wall. Cellulases are 99
also known to be associated with abscission and dehiscence processes in many plant species 100
(Abeles, 1969; Lashbrook et al., 1994; del Campillo and Bennett, 1996; Gonzalez-Bosch et al., 101
1997; Trainotti et al., 1997; Lane et al., 2001; Du et al., 2014). Along with the pectinase genes, 102
expression of a cellulase gene in the pedicel abscission zone is also dependent on the J, MC, and 103
SIMBP21 transcription factors in tomato (Nakano et al., 2015). Genetic evidence shows that the 104
cellulase encoded by the RSW2 gene functions in anther dehiscence in Arabidopsis (Lane et al., 105
2001). Like pectinases, cellulases also act in fleshy fruit ripening (Christoffersen et al., 1984; 106
Lashbrook et al., 1994; Harpster et al., 1997). 107
In addition to the abovementioned functions in late developmental processes, pectinases and 108
cellulases also act in cell differentiation in early developmental processes. The pectinase ZePG1 109
is localized on the secondary wall thickenings of differentiating tracheary elements and phloem 110
regions in Zinnia elegans, suggesting a role for ZePG1 in the differentiation of tracheary 111
elements and other cells (Nakashima et al., 2004). A tomato pectinase is also predicted to 112
function in vascular tissue differentiation in addition to its role in seed germination (Sitrit et al., 113
1999). Expression of the tomato cellulase, Cel4, is correlated with rapid cell expansion in pistils, 114
hypocotyls, and leaves (Brummell, et al., 1997). Similarly, the Arabidopsis cellulase 115
KORRIGAN is also correlated with rapid cell elongation, and the korrigan mutant is an extreme 116
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dwarf with pronounced alterations in the primary cell wall, revealing that cellulose modifications 117
by KORRIGAN is coupled to cellulose synthesis in the cell wall (Nicol et al., 1998; Lane et al., 118
2001). Interestingly, the pectin composition in the cell wall in korrigan is affected even though 119
KORRIGAN is not expected to directly affect pectin metabolism (His et al., 2001). Homologs of 120
KORRIGAN also participate in cellulose formation in the secondary wall in Populus (Yu et al., 121
2014). Moreover, another xylem-specific cellulase in Populus is required for normal secondary 122
cell wall formation in the xylem (Yu et al., 2013). 123
Because hemicellulose is another common component of plant cell walls (Heredia et al., 1995), 124
plant hemicellulases are expected to play roles similar to those of cellulases and pectinases in 125
plant development. However, available experimental evidence showing the functions of plant 126
hemicellulases in plant development is very limited. To our knowledge, to date, the biological 127
functions of plant hemicellulases have been established only for the seed germination process 128
(Iglesias-Fernández et al., 2011; Martínez-Andújar et al., 2012; Iglesias-Fernández et al., 2013). 129
Twenty-five cellulase genes (Urbanowicz et al., 2007) and eight mannanase (enzyme 130
catalyzing the degradation of mannan, a type of hemicellulose molecule) genes (Yuan et al., 131
2007) have been predicted to exist in the Arabidopsis genome. None of these genes has been 132
shown to act in a dehiscence process in Arabidopsis. Here, we show that CELLULASE 6 (CEL6) 133
and MANNANASE 7 (MAN7) likely indirectly affect the timing of cell differentiation in the 134
silique valve and promote silique dehiscence by facilitating cell disintegration in the separation 135
layer. We also show that loss-of function mutations of CEL6, MAN7, ADPG1 and ADPG2 136
reduce the ability of the silique to dehisce in an additive fashion. Our results may be useful for 137
engineering crops with desired dehiscence kinetics. 138
139
RESULTS 140
141
CEL6 and MAN7 Are Expressed in the Silique and Their Expression Is Partially 142
Dependent on IND and ALC 143
144
To identify genes that encode uncharacterized cell wall-degrading enzymes that function in 145
silique dehiscence in Arabidopsis, we first conducted in silico searches (see Methods). This 146
effort resulted in the identification of 39 cellulase and other cell-wall degrading enzyme genes 147
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(Table S1). To determine which of these genes are expressed at a relatively high level in late 148
silique development, we searched their mean-normalized expression levels in siliques with seeds 149
containing late heart to mid-torpedo embryos using the AtGenExpress Visualization Tool 150
(http://jsp.weigelworld.org/expviz/expviz.jsp?experiment=development&normalization=normali151
zed&probesetcsv). The chosen stage is the latest available for microarray experiments with 152
silique tissue, which should fall within flower development stage 17 (Smyth et al., 1990; Le et al., 153
2010). We decided to select the genes that have a mean-normalized expression level of > 1 at this 154
stage, which yielded 12 genes (Table S2). We next determined which of the 12 genes are 155
coexpressed with the transcription factor gene ALC in ATTED-II (http://atted.jp/) because ALC 156
is a basic helix-loop-helix (bHLH) transcription factor that positively regulates silique 157
dehiscence (Rajani and Sundaresan, 2001). Only two of the 12 genes, AT4G39010 and MAN7 158
(AT5G66460), were found to be within the first 1000 genes coexpressed with ALC. AT4G39010 159
encodes a cellulase (Urbanowicz et al., 2007) and MAN7 encodes a hemicellulase. For 160
convenience and clarity, hereafter, AT4G39010 is named CELLULASE 6 (CEL6), following the 161
previously designated CEL1–5 (Shani et al., 1997; Yung et al., 1999; del Campillo et al., 2004; 162
Urbanowicz et al., 2007). 163
To confirm and further characterize the expression of the above identified genes, we conducted 164
reverse transcription-quantitative polymerase chain reaction (RT-qPCR) experiments for the 165
transcripts of CEL6 and MAN7 during stages 17 and 18 of floral development in the wild type 166
(Col-0). Stage 17 starts when all the floral organs (not including the carpels) shed and ends with 167
the silique turning yellow, and stage 18 is marked by the yellow and yet not dehisced silique 168
(Smyth et al., 1990). In this investigation, we further divide stage 17 into 17A (approximately 4-169
6 days after anthesis) and 17B (approximately 6-12 days after anthesis), stage 18 into 18A (light 170
yellow) and 18B (yellow), and stage 19 into 19A (initial dehiscence) and 19B (dehiscence 171
extended from an initial dehiscence area) (Fig. S1). CEL6 and MAN7 were expressed at 172
relatively high levels throughout stage 17, and MAN7 even attained its highest expression level at 173
stage 18B (Fig. 1A and B). We therefore focused on CEL6 and MAN7 in subsequent 174
investigation for their likely relevance to silique dehiscence based on the expression results. 175
We next determined the expression levels of CEL6 and MAN7 in late stage-17 (10 days after 176
anthesis) siliques of Col-0, the ind-7 mutant, and the alc-3 mutant to test if their expression is 177
regulated by IND and ALC. IND is also a bHLH transcription factor and a major regulator of 178
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silique dehiscence (Liljegren et al., 2004; Wu et al., 2006; van Gelderen et al., 2016), but it was 179
not included in the earlier coexpression screening for silique dehiscence-related wall-degrading 180
enzyme genes because it is absent in the microarray data due to its highly specific expression in a 181
small number of cells in the dehiscence zone. The mutants ind-7 (SALK_058083) and alc-3 182
(SALK_103763) are newly identified alleles that each exhibited an indehiscent phenotype 183
similar to those of previously reported ind and alc alleles (Liljegren et al., 2004; Wu et al., 2006; 184
Rajani and Sundaresan, 2001). RT-qPCR studies indicated that ind-7 and alc-3 were null or 185
nearly null alleles (Fig. S2). We chose ind-7 and alc-3 because they and other plant lines used in 186
this investigation were in the Col-0 background, which provided a condition for consistent 187
comparisons of phenotypes and gene expression levels. The transcript levels of CEL6 in ind-7 188
and alc-3 were approximately 30% and 60% of the wild-type level, respectively (Fig. 1C). The 189
transcript levels of MAN7 in ind-7 and alc-3 were approximately 25% and 35% of the wild-type 190
level, respectively (Fig. 1D). These results indicate that IND and ALC positively regulate the 191
expression of CEL6 and MAN7 in late stage-17 siliques, validating and extending the in silico 192
findings that CEL6 and MAN7 are expressed in stage-17 siliques and coexpressed with ALC. 193
194
Expression Domains of CEL6 and MAN7 Largely Overlap in Vegetative and Reproductive 195
Organs and Shift in Location during Silique Development 196
197
To investigate whether CEL6 and MAN7 are expressed in tissues that are relevant to silique 198
dehiscence, we generated transgenic lines harboring either the pCEL6:β-glucuronidase (GUS) 199
transgene or pMAN7:GUS transgene. In the seedlings of the pCEL6:GUS lines, the GUS signal 200
was detected throughout the cotyledons and first leaf, but the signal was increasingly restricted to 201
the margins and vascular tissue in later formed leaves (Fig. S3A-E). The GUS signal was in the 202
root and root primordia except the mature root tip, and the junction region between the root and 203
the hypocotyl is highly stained for the GUS signal (Fig. S3F-H). The GUS signal was also in 204
parenchyma cells of seed coat origin (Fig. S3I). In the inflorescence, the GUS signal was in all 205
floral organs and pollen, and in young siliques (stages13-16) the GUS signal was mostly in the 206
basal region and the stigma-style region (Fig. S3J-L and Fig. S4A and B). In stage-17 siliques, 207
the GUS signal appeared to diminish (Fig. S4C-F). However, in stage-18 siliques, new GUS 208
signal appeared mostly in the region encompassing the replum and the valve margins and in the 209
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funiculi (Fig. 2A and B). The patterns of GUS signal in the pMAN7:GUS plants were almost 210
identical as those in the pCEL6:GUS plants (Fig. S5 and Fig. 2I and J), except that the signal was 211
also observed in the root cap (Fig. S5F). 212
To further validate the expression patterns of CEL6 and MAN7, we created Arabidopsis lines 213
that expressed the CEL6-GUS fusion protein by the pCEL6:CEL6-GUS transgene or the MAN7-214
GUS fusion protein by the pMAN7:MAN7-GUS transgene. GUS staining of these lines showed 215
that these fusion proteins were expressed in patterns overall similar to those observed with their 216
promoter-GUS lines (Fig. S3-7 and Fig. 2A-D and I-L). The GUS signal was weaker and more 217
restricted to certain regions in some of the vegetative and reproductive organs but stronger in the 218
style before stage 17 in the pCEL6:CEL6-GUS lines than in the pCEL6:GUS lines (Fig. S3, Fig. 219
S4A-L, and Fig. S6). A similar trend was observed in the vegetative organs for the 220
pMAN7:MAN7-GUS and pMAN7:GUS lines, with the GUS signal being weaker in the former 221
lines, except that the GUS signal was stronger in the vasculature in the leaves of pMAN7:MAN7-222
GUS plants than in those of pMAN7:GUS plants(Fig. S5A-I and Fig. S7A-I). The GUS signals in 223
the reproductive organs appeared to be at similar or higher levels in the pMAN7:MAN7-GUS 224
lines compared with those in the pMAN7:GUS lines (Fig. S4M-X, Fig. S5J-L, Fig. S7J-L, and 225
Fig. 2I-L). Compared with the pMAN7:GUS lines, at stages 15 and 16, the GUS signal in the 226
pMAN7:MAN7-GUS lines extended from the base and the style of the silique into the valves, but 227
the valves still appeared to be free of the signal along most of their lengths. In stage-18 siliques, 228
for both CEL6 and MAN7, the GUS signals were overall similar in intensity and location 229
between the promoter-fusion and protein-fusion lines (Fig. 2A-D and I-L). Semi-thin sections of 230
GUS-stained stage-17B siliques of the four types of transgenic lines further showed that the GUS 231
signals were mostly in the valve margins and the replum (Fig. S8). These results indicate that the 232
expression domains of CEL6 and MAN7 largely overlap in vegetative and reproductive organs 233
and developmentally shift in location in the silique. 234
235
Expression of CEL6 and MAN7 Is Reduced in Late Silique Development in ind-7 and alc-3 236
237
Because IND and ALC are specifically expressed in the valve margin in late silique development 238
(Liljegren et al., 2004; Wu et al., 2006; Rajani and Sundaresan, 2001) and the RT-qPCR results 239
showed that the expression of CEL6 and MAN7 are partially dependent on IND and ALC, we 240
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tested whether the reduced expression of CEL6 and MAN7 occurs in the valve margin in the ind-241
7 and alc-3 mutants. We introduced the pCEL6:GUS or pMAN7:GUS constructs into these 242
mutants by crossing and GUS-stained stage-18 siliques from the mutant plants containing one of 243
the two transgenes. The results show that the GUS signal from either pCEL6:GUS or 244
pMAN7:GUS was absent or at a very low level in the valve margins but retained in the replum 245
region and the funiculi in ind-7 (Fig. 2A, B, E, F, I, J, M and N). Similar results occurred with 246
the GUS signals in alc-3 (Fig. 2A, B, G, H, I, J, O and P). These results are consistent with the 247
results in Fig. 1C and D, suggesting that IND and ALC positively regulate the expression of 248
CEL6 and MAN7 in the valve margin. 249
250
Identification of the cel6 and man7 Mutants 251
252
To investigate the functions of CEL6 and MAN7 in silique development, we obtained two T-253
DNA-insertion mutant alleles for each of the two genes (see also METHODS). By conducting 254
PCRs to detect the presence of a T-DNA insertion, we confirmed the locations of the T-DNA 255
insertions in these mutants as described in TAIR (Fig. S9). The cel6-1 mutant (SALK_060505C) 256
had a T-DNA insertion at a position 86 bp upstream of the start codon of CEL6, and cel6-2 257
(WiscDsLox485-488K15) had a T-DNA insertion in the first exon of CEL6 (Fig. 3A). The 258
man7-1 mutant (GABI_747H02), which was previously characterized as a mutant defective in 259
seed germination (Iglesias-Fernández et al., 2011), has a T-DNA insertion in the 5’-UTR (12 260
base pairs from the start codon) of MAN7, and the man7-3 mutant (SAIL_424_H03) has a T-261
DNA insertion in the fourth intron of MAN7 (Fig. 3A). We then investigated the transcript levels 262
of the two genes in stage-17 siliques of the mutants and the Col-0 control by RT-qPCR. Results 263
from this investigation showed that the transcript levels of CEL6 and MAN7 in their respective 264
mutants were approximately 14% (in cel6-1), 6% (in cel6-2), 14% (in man7-1), and 0.2% (in 265
man7-3) of the wild-type level (Fig. 3B and C), suggesting that they were null or nearly null 266
alleles. 267
268
Cell Differentiation in the Dehiscence Zone Is Delayed in Early Stage 17 Siliques of cel6 269
and man7 Mutants 270
271
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In the process of characterizing the phenotypes of the cel6 and man7 mutants, we observed that 272
silique development in these mutants were delayed compared to the wild type. In particular, 273
progression of silique development from stage 15 to stage 18A in Col-0, on average, took 14 274
days, while the same developmental process was significantly delayed by two to three days in the 275
single and the double mutants (t-test, p < 10-36, n =50). Because most of the silique elongation 276
and lateral enlargement occurs in stage 17 and our initial goal of the research was to determine 277
the roles of CEL6 and MAN7 in silique dehiscence, we first focused on the cellular features in 278
the dehiscence zone in stage-17 siliques. The dehiscence zone in an Arabidopsis silique is a 279
longitudinally narrow region where small centrally located parenchyma cells in the separation 280
layer are flanked by a group of cells with thickened and lignified cell walls on the valve side and 281
relatively large parenchyma cells on the replum side (Wu et al., 2006). In siliques of Col-0, four, 282
six, eight, and 10 days after anthesis, the lignified cells in the dehiscence zone were readily 283
observed (Fig. 4A1, B1, C1, D1). It was difficult to detect such cells in the cel6 and man7 single 284
mutants and the cel6-1 man7-3 double mutant four days after anthesis as the cells in the 285
corresponding region had thin cell walls (Fig. 4A2-6). Such cells in the valve margin were 286
convincingly observed in the single mutants 6 days after anthesis (Fig. 4B2-5), but not in the 287
cel6-1 man7-3 double mutant (Fig. 4B6). Only at the subsequent stages, i.e., eight days and 10 288
days after anthesis, did these cells in the double mutant appear to attain wall thicknesses similar 289
to those in Col-0 and the single mutants at the corresponding stages (Fig. 4C1-6 and D1-6). 290
These observations indicate that mutations in these genes cause a delay in secondary wall 291
thickening in this group of cells in the valve margin, and the double mutant had a more severe 292
phenotype in this regard than the single mutants. CEL6 and MAN7 proteins, therefore, normally 293
promote secondary wall thickening in this group of cells in the valve margin. 294
The cells of the separation layer are expected to undergo programmed cell death (PCD) during 295
silique development. Morphological characteristics of plant cell PCD include ameboid-shaped 296
nuclei, condensed chromatin, and cellular disorganization (Vanyushin et al., 2004; van Doorn et 297
al., 2011; Bar-Dror et al., 2011). Ameboid-shaped nuclei and condensed chromatin near the 298
nuclear periphery were observed in the separation layer four days and/or six days after anthesis 299
in the wild type (Fig. S10A-D) and the mutants (Fig. S10G-J and M-P). Degenerated cells 300
without the typical cytoplasm-nuclear organization were observed in the separation layer at late 301
stage 17 (Fig. S10E, F, K, L, Q and R). To further characterize PCD in the separation layer, we 302
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11
conducted the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) 303
assay to detect nuclear DNA fragmentation, a hallmark of PCD (Bar-Dror et al., 2011), with 304
sections of siliques of three to 13 days after anthesis. In Col-0, strong TUNEL signals were first 305
detected in a region that overlapped with the separation layer (between the fluorescent lignified 306
cells in the valve margin and the replum) four days after anthesis (Fig, 5B). Strong signals were 307
also detected five days after anthesis but not at other stages in the same region in Col-0 (Fig. 5A, 308
C and D; Fig. S11A-D). In the cel6-1, cel6-2, man7-1, and man7-3 mutants, strong signals were 309
detected in the same region only five days after anthesis (Fig. 5F, J, N and R) but not at other 310
stages (Fig. 5E, G-I, K-M, O-Q, S and T; Fig. S11E-T). The same results were obtained in at 311
least three siliques for each genotype at each stage. Thus, PCD in the separation layer starts at 312
early stage 17 in the wild type and the mutants, and is delayed in the mutants. In Fig. 5, the 313
fluorescence of the lignified cells in the valve margin apparently resulted from the thickened 314
secondary cell walls. Such fluorescent cell walls first appeared in Col-0 siliques four days after 315
anthesis (Fig. 5B), whereas in the siliques of the mutants it seemed to first weakly appear five 316
days after anthesis (Fig. 5F, J, N and R). The delayed occurrence of the fluorescent cell walls in 317
the valve margin is consistent with the delayed secondary wall thickening in these cells described 318
earlier (Fig. 4). The effects of the mutations on the delay of cell differentiation in the dehiscence 319
zone were observed in cross sections at different locations along the longitudinal axis of the 320
siliques. As reported earlier, the expression of CEL6 and MAN7 in the silique is only in the 321
apical (including the stigma, style, and adjacent fruit wall) and basal regions prior to and during 322
stage 17 (Fig. S4). The observed developmental delay in the dehiscence zone thus likely 323
indirectly results from the loss of function in CEL6 or MAN7. 324
325
Cell Morphology and Integrity in the Separation Layer in Late Silique Development Are 326
Altered in cel6 and man7 Mutants 327
328
Because CEL6 and MAN7 are expressed in the dehiscence zone in late silique development (Fig. 329
2A-D and I-L), we predicted that CEL6 and MAN7 participate in the degradation of cell walls in 330
the separation layer. Indeed, cell walls in the separation layer in the wild type appeared to be 331
weakened towards late stage 17 as the walls were wavy and the neighboring cells were 332
increasingly interdigitated (Fig. S10C-E), in contrast with the lack of such changes in the 333
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mutants even at late stage 17 (Fig. S10I-K and O-Q). The cell size and shape in the separation 334
layer also appeared to differ between the wild type and the mutants presumably due to the 335
difference in cell wall rigidity between them when the cells were under stress and/or strain. We 336
thus measured the cell lengths and widths in the separation layer in TEM images of late stage-17 337
siliques in the wild type and the mutants, and calculated the length-to-width ratio and the area 338
(product of the length and width) of each measured cell. The ratio and area were deemed to be 339
indicators of the cell shape and size, respectively. The average length-to-width ratio of Col-0 340
siliques was 1.44 ± 0.04 (standard error), which was significantly smaller than the averages 341
(between 1.62 and 1.75 with standard errors ranging from 0.05 to 0.1) of the cel-6 and man-7 342
single mutants and the cel6-1 man7-3 double mutant (Fig. 6A; t-test, p ≤ 0.02). The average cell 343
area of Col-0 was 15.0 ± 1.3 µm2, which was significantly larger than those of cel6-1 (10.7 ± 1.1 344
µm2), cel6-2 (10.5 ± 1.0 µm2), man7-3 (11.2 ± 1.1 µm2), and cel6-1 man7-3 (8.6 ± 0.8 µm2) (Fig. 345
6B; t-test, p ≤ 0.03), although it was not significantly different from that of man7-1 (12.3 ± 1.1 346
µm2) (Fig, 6B; t-test, p = 0.13). These results indicate that the mutations altered the cell shape 347
and size in the separation layer in the single and double mutants. The greater effect of the 348
mutations on the cell size in the double mutant compared to that in the single mutants suggests 349
that the mutations in the two genes are additive in affecting cell morphology in the separation 350
layer. 351
To obtain additional evidence that the mutations affect separation layer in late silique 352
development, we further investigated cell morphology in the separation layer in late stage-17 and 353
stage-18 siliques in the wild type and mutants. We first noticed that the cells in the separation 354
layer were not as organized and distinct in the Col-0 accession as in the Ler accession (Fig. 7; 355
Wu et al., 2006). The cells in the separation layer near the inner epidermis were disintegrating at 356
late stage 17 in Col-0 (Arrow, Fig. 7A1), but such cells remained intact in all the single mutants 357
and the double mutant at the corresponding stage (Fig. 7A2-6). At stage 18A, the siliques of Col-358
0 were usually easily shattered along the separation layer during specimen preparation for the 359
TEM study, although most of the cells in separation layer, except the small cells near the inner 360
epidermis, were still intact (Fig. 7B1). The siliques of the single mutants and the double mutant 361
usually remained indehiscent during specimen preparation for the TEM study, and all cells in the 362
separation layer remained intact (Fig. 7B2-6). Cells in the separation layer in Col-0 all seemed 363
broken at stage 18B in the sections (Fig. 7C1). By contrast, most, if not all, cells of the 364
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separation layer in the single mutants and the double mutant remained intact at stage 18B (Fig. 365
7C2-6). These observations suggest that cell walls in the separation layer in the mutants were 366
stronger than those in the wild type, preventing the bursting of these cells during the sample 367
preparation process. CEL6 and MAN7, therefore, are involved in the degradation of cell walls in 368
the separation layer during silique maturation. 369
370
Silique Dehiscence Is Impaired in cel6 and man7 mutants 371
372
The siliques of the cel6 and man7 single and double mutants could dehisce but their dehiscence 373
appeared to occur at lower percentages (dehiscence rates) than the siliques of Col-0 during the 374
transition from stage 18B to stage 19. To quantify these differences, we investigated the 375
dehiscence rates of two consecutive siliques on the same inflorescence stem for the mutant and 376
Col-0 samples. The younger one of these two siliques was at a stage between 18B and 19A (14 377
and 16 days after anthesis for Col-0 and the mutant lines, respectively), i.e., a still hydrated 378
yellow silique that might or might not have dehisced (Fig. S12). By choosing these consecutive 379
siliques in this developmental window, we likely captured siliques that were undergoing initial 380
dehiscence, thus revealing how easily siliques dehisced on a plant. The chosen siliques were 381
subject to careful examination under a dissecting scope to determine if they dehisced. Of the Col-382
0 plants, the average dehiscence rates of siliques at these two slightly different stages were 76% 383
and 100%, respectively (Fig. 6C). The average dehiscence rates of the younger siliques of the 384
single and double mutants ranged from 10-39%, and the average dehiscence rates of the older 385
siliques 42-82%, significantly less than those of Col-0, respectively (t-test, p < 10-5; Fig. 6C). 386
The average dehiscence rates of the younger and older siliques of the cel6 mutants did not 387
statistically differ from those of the double mutant, but they were significantly lower than those 388
of the man7 mutants, respectively (t-test, p < 0.02; Fig. 6C). These results indicate that the cel6 389
and man7 mutations impaired silique dehiscence, and the cel6-1 mutation was epistatic to the 390
man7-3 mutation with respect to the dehiscence rate. 391
To further investigate the functions of CEL6 and MAN7, we overexpressed CEL6 or MAN7 in 392
Col-0 using the cauliflower mosaic virus 35S promoter. We observed that overexpression of 393
CEL6 and MAN7 either did not promote or only moderately promoted silique dehiscence in the 394
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transgenic lines (Fig. S13), indicating that CEL6 and MAN7 are not major limiting factors for 395
silique dehiscence in wild-type Arabidopsis. 396
397
The Silique Indehiscent Phenotypes of adpg1-1 and adpg1-1 adpg2-1 Are Enhanced by the 398
cel6-1 and man7-3 Mutations 399
400
A previous investigation indicated that the pectinases ADPG1 and ADPG2 play a major and 401
minor role, respectively, in silique dehiscence in Arabidopsis (Ogawa et al., 2009). Our 402
investigation demonstrates that a cellulase (CEL6) and a hemicellulase (MAN7) also participate 403
in silique dehiscence. To compare the effects of loss of function in one or more of these genes on 404
silique dehiscence, all possible double, triple, and quadruple mutant lines of these four loci were 405
generated. TEM characterization of cell morphology in the region encompassing the valve 406
margin and the replum in stage-18B siliques was conducted. The adpg1-1 mutant siliques 407
underwent incomplete dehiscence with collapsed or broken cells in the separation layer in the 408
prepared samples (Fig. 8A). The adpg2-1 exhibited complete dehiscence with collapsed or 409
broken cells in the separation layer (Fig. 8E). These observations are consistent with adpg1-1 410
and adpg2-1 having a severe indehiscent phenotype and a mild indehiscent phenotype, 411
respectively. In both of these mutants, cell degeneration occurred at the separation layer. The 412
cel6-1 adpg1-1 double mutant was indehiscent with mostly intact cells at the separation layer 413
(Fig. 8B). The man7-3 adpg1-1 double mutant exhibited cellular morphology similar to that in 414
adpg1-1 but it appeared to have more intact cells in the separation layer than adpg1-1 did (Fig. 415
8A and C). The cel6-1 man7-3 adpg1-1 triple mutant appeared similar in cell morphology at the 416
separation layer to cel6-1 adpg1-1 (Fig. 8B and D). These observations suggest that the effects of 417
the adpg1-1, cel6-1, and man7-3 mutations on the cells in the separation layer were additive, 418
with adpg-1 being primarily defective in cell separation at the middle lamella and cel6-1 and 419
man7-3 being primarily defective in cell lysis. It is also likely that the CEL6 protein plays a 420
greater role in cell lysis at the separation layer than MAN7 does in the normal silique dehiscence 421
process, given the different severity levels of cell disintegration shown in Fig. 8B and C. 422
Similar to the adpg2-1 single mutant, siliques of the double and triple mutants involving 423
adpg2-1, cel6-1, and man7-3 all dehisced, but they showed intact cells in the separation layer in 424
the processed samples (Fig. 8F-H). Siliques of all the other triple and quadruple mutants in Fig. 8 425
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did not dehisce and contained intact cells in the separation layer in the processed samples (Fig. 426
8I-L), further demonstrating that mutations in the pectinases and the cellulase and hemicellulase 427
primarily affect cell separation at the middle lamella and cell lysis in this region, respectively. 428
We also compared the silique dehiscence rates during the stage 18B-19A transition in the 429
above lines. The adpg1-1 mutant had very low dehiscent rates for the two consecutive siliques on 430
the same branch, which were not significantly different from those of the double mutants cel6-1 431
adpg1-1 and man7-3 adpg1-1, and the triple mutant cel6-1 man7-3 adpg1-1 (Fig. 9A; t-test, p > 432
0.05). The double mutant cel6-1 adpg2-1 had lower and higher dehiscent rates than the adpg2-1 433
mutant and cel6-1 mutant, respectively (Fig. 9A; t-test, p ≤ 0.01). The average dehiscence rates 434
of the double mutant man7-3 adpg2-1 did not differ significantly from those of the man7-3 and 435
adpg2-1 single mutants (Fig. 9A; t-test, p > 0.14). These results did not clearly indicate whether 436
cel6-1 or man7-3 further enhanced the silique indehiscent phenotype caused by the adpg1-1 437
mutation. On the other hand, cel6-1, but not man7-3, seemed to enhance the silique indehiscent 438
phenotype caused by the adpg2-1 mutation. 439
Even though the siliques of the cel6-1 adpg1-1 and man7-3 adpg1-1 double mutants and the 440
cel6-1 man7-3 adpg1-1 triple mutant all had low dehiscence rates, and the siliques of the adpg1-441
1 adpg2-1 double mutant, the cel6-1 adpg1-1 adpg2-1 and man7-3 adpg1-1 adpg2-1 triple 442
mutants, and the quadruple mutants were all indehiscent (Fig. 9A), they might still differ in their 443
ability to dehisce under a mechanical force. To test this prediction, we subjected yellow and 444
dried siliques of these genotypes, adpg1-1, and the indehiscent mutants ind-7 and alc-3 to a 445
centrifugation force (18000 g) for one minute in microcentrifuge tubes, and then investigated 446
their dehiscence rates. The results showed that, on average, approximately 80% of the siliques 447
of adpg-1-1 dehisced after the centrifugation, which was significantly higher than those of cel6-1 448
adpg1-1, man7-3 adpg1-1, and cel6-1 man7-3 adpg1-1 (Fig. 9B; t-test, p < 0.04). On average, 449
approximately 27% of the siliques of adpg1-1 adpg2-1 also dehisced after the centrifugation, 450
which was significantly higher than those of man7-3 adpg1-1 adpg2-1 (Fig. 9B; t-test, p < 10-4). 451
The siliques of the cel6-1 adpg1-1 adpg2-1 triple mutant, the quadruple mutant, and the ind-7 452
mutant remained indehiscent after the centrifugation, while the siliques of the alc-3 mutant had 453
an average dehiscence rate of approximately 3% (Fig. 9B). These results revealed that the cel6-1 454
and man7-3 mutations enhanced the silique indehiscent phenotypes caused by the adpg1-1 455
mutation and the adpg1-1 adpg2-1 double mutations. There results also showed that the ind-7 456
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16
and alc-3 mutants exhibited stronger silique indehiscent phenotypes than any of the single and 457
double mutants and two of the triple mutants of the cell wall-degrading enzyme genes (Fig. 9B). 458
459
DISCUSSION 460
461
Multiple Classes of Cell Wall-degrading Enzymes Participate in the Same Developmental 462
Processes 463
464
Cell wall modifications are an integral part of plant development. Multiple components of the 465
cell wall are likely modified during development, and each modification is catalyzed by a 466
distinct class of cell wall-degrading enzyme. In this investigation, we found that cel6 and man7 467
mutants exhibited similar defects in silique development and dehiscence, and their expression 468
patterns are also similar in vegetative and reproductive organs. These observations strongly 469
suggest that cellulases and hemicellulases participate in the same developmental processes. 470
Together with the findings of the roles of ADPG1 and ADPG2 in silique dehiscence (Ogawa et 471
al., 2009), all three major classes of cell wall-degrading enzymes are now found to act in silique 472
dehiscence. It will be interesting to explore whether the three classes of enzymes also modify cell 473
walls in other developmental processes. It may be a paradigm that two or three classes of cell 474
wall-degrading enzymes need to act on the same cell wall in the same time window to efficiently 475
complete the cell wall changes required for normal growth and differentiation of a cell. After all, 476
cellulase-hemicellulase complexes are widely used by bacteria and fungi to efficiently degrade 477
plant materials (Dollhofer et al., 2015; Bensoussan et al., 2017). Regardless of whether or not the 478
enzymes form a complex, the expression of cell wall-degrading enzymes such as CEL6, MAN7, 479
and ADPG1 is likely regulated by the same transcription factors (Ogawa et al., 2009; this 480
investigation). 481
Our GUS-reporters indicate that both CEL6 and MAN7 are expressed in two homologous 482
structures, the leaf margin and the silique valve margin. It is possible that cell differentiation in 483
the leaf margin, as in the silique margin, needs the activities of CEL6, MAN7, and possibly other 484
cell-wall-degrading enzymes. CEL6, MAN7, ADPG1, and/or ADPG2 also share similar GUS 485
staining patterns in the seed coat, funiculus/seed dehiscence zone, leaves, and floral organs 486
(Ogawa et al., 2009; Iglesias-Fernández et al., 2013; this investigation), which suggests that their 487
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17
expression is under the control of a common mechanism and the biological processes require the 488
coordinated actions of the three classes of cell wall-degrading enzymes. 489
490
Dehiscence and Abscission Likely Involve Both Cell Separation and Degeneration in 491
Arabidopsis 492
493
Cell separation must occur in all dehiscence and abscission processes. Cell separation alone, 494
without cell degeneration, can conceivably lead to dehiscence or abscission. However, in 495
Arabidopsis silique dehiscence, as demonstrated in this report, both cell separation and 496
degeneration occur in the separation layer. More importantly, both cell separation and 497
degeneration influence the ability of the silique to dehisce, even though the former plays a bigger 498
role than the latter. Based on the observation that CEL6 and MAN7 are co-expressed in multiple 499
dehiscence and abscission zones in Arabidopsis, it may be predicted that cell degeneration occurs 500
in multiple dehiscence and abscission processes. In fact, cell degeneration has been found to be 501
associated with anther dehiscence in Arabidopsis (Sanders et al., 2000). Drawn upon from the 502
Arabidopsis silique dehiscence case, it appears that the combination of cell separation and 503
degeneration can make a dehiscence or an abscission process occur more easily than just cell 504
separation. 505
506
How Do CEL6 and MAN7 Indirectly Affect Silique Development during Stage 17? 507
508
Studies of various cell wall-degrading enzymes in plants have indicated that cell wall-degrading 509
enzymes are directly involved in cell differentiation during plant development (Brummell, et al., 510
1997; Nicol et al., 1998; Sitrit et al., 1999; Lane et al., 2001; Nakashima et al., 2004; Yu et al., 511
2013; Yu et al., 2014). However, CEL6 and MAN7 seem to be indirectly involved in cell 512
differentiation in the silique dehiscence zone during stage 17, based on their spatio-temporal 513
expression patterns in stage-17 siliques in the promoter- and protein-GUS fusion lines, and the 514
delayed secondary wall thickening and onset of the TUNEL signals in the dehiscence zone in 515
their mutants. Then, how may CEL6 and MAN7 indirectly exert such effects? One possible 516
answer to this question may be that the cel6 and man7 mutations slow down pollen tube growth, 517
which delays fertilization and subsequent cell differentiation in the silique wall. It is known that 518
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the silique does not elongate if no fertilization occurs in Arabidopsis, underscoring the 519
dependence of post-anthesis silique development on the fertilization event. CEL6 and MAN7 are 520
expressed in the pollen, the stigma, and the style prior to and during pollination (Fig. S3 to Fig. 521
S7). Cells at any of these locations in the mutants may negatively impact pollen tube growth. To 522
determine whether pollen tube growth is slowed at a particular step in the pollination-fertilization 523
process and whether fertilization and the subsequent silique development are delayed in the 524
mutants, likely requires extensive studies of in vitro and in vivo pollen tube growth, embryo and 525
seed development, and silique wall development outside the dehiscence zone in the mutants and 526
the wild type. 527
528
The Ability of a Plant Part to Dehisce Can Be Manipulated to Both Large and Small 529
Degrees Depending on the Type of Genes Altered 530
531
The dehiscence rates of the mutants in this investigation vary greatly, ranging from zero even 532
under the centrifugation condition to close to the wild type value when not centrifuged. A pattern 533
also emerged in these plant lines: the mutants of the transcription factors, ind-7 and alc-3, 534
showed the strongest indehiscent phenotype, followed by, in the order of increasing dehiscence 535
rates, the adpg1-1, cel6, man7, and adpg2-1 mutants. These results are consistent with the 536
hypothesis that IND and ALC are at the top of the hierarchy of regulation, and command the 537
expression of numerous downstream genes involved in the dehiscence process. The major 538
pectinase for silique dehiscence, ADPG1, ought to play a bigger role in the dehiscence processes 539
than the cellulase CEL6 and hemicellulase MAN7 since its action on the pectin-rich outer cell 540
wall layer is expected to impact dehiscence much more than the actions of CEL6 and MAN7 on 541
the inner cell wall layer, which is rich in cellulose and hemicellulose. Even the more severe 542
indehiscent phenotypes of the cel6 mutants compared to those of the man7 mutants may be 543
explained by differential contributions of the cellulose and hemicellulose components of the cell 544
wall to maintaining cell integrity in the separation layer. Our observations of the different 545
dehiscence rates among the lines have potential implications to engineering desired dehiscent 546
kinetics in crop species. Crop parts harvested for food often are concerned with the dehiscence of 547
these parts. Different levels of an indehiscent trait may be desired for different crops and/or 548
different storage and harvesting strategies. Our results demonstrate that the ability of a plant part 549
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19
to dehisce can be manipulated to different degrees by targeting the activities of different proteins 550
involved in the dehiscence process. 551
552
CONCLUSION 553
554
By analyzing mutant phenotypes and gene expression patterns, we demonstrate that CEL6 and 555
MAN7 affect cell differentiation in the silique and contribute to silique dehiscence. We also 556
show that the ability of the silique to dehisce is differentially affected by the loss of function in 557
the number and types of genes involved in the process. 558
559
METHODS 560
561
In Silico Screening 562
563
“Cellulase” was first used as a keyword to query www.arabidopsis.org to find cellulase genes. 564
Protein sequences of these genes were used to perform BLAST searches in www.arabidopsis.org 565
and www.ncbi.nlm.nih.gov/blast/Blast.cgi to identify additional cellulase and hemicellulase 566
genes. Further identification of CEL6 and MAN7 as candidates for cell wall-degrading enzyme 567
genes functioning in stage-17 siliques was based on their expression levels and coexpression 568
with ALC according to publicly available microarray data (see also Results). 569
570
Plant Materials and Growth Conditions 571
572
All Arabidopsis thaliana lines used in this study were in the Col-0 background. All mutant lines 573
were obtained from the Arabidopsis Biological Resource Center at the Ohio State University 574
(Columbus, Ohio, USA), except for the man7-1 and adpg1-1 mutant lines that were from 575
Nottingham Arabidopsis Stock Centre at The University of Nottingham (Nottingham, UK). 576
Plants were grown under long-day conditions (16 h light/8 h dark) at approximately 22℃ in a 577
growth room or grow chamber on artificial soil or an agar medium at pH 5.7. The agar medium 578
consisted of 4.3g/L Murashige and Skoog salt mixture (Gibco, Thermo Fisher Scientific, 579
Waltham, Massachusetts, USA), 1% (w/v) sucrose, and 0.8% (w/v) agar. For transgenic plant 580
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20
selection, antibiotics were added to the agar medium when the medium was cooled to 581
approximately 60℃. 582
583
RNA Extraction and Analysis 584
585
RNA samples were extracted using an RNeasy® Plant Mini Kit (QIAGEN, Germantown, 586
Maryland, USA) or E.Z.N.A.® Plant RNA Kit (Omega Bio-tek, Norcross, Georgia, USA) 587
according to the manufacturers’ protocols. The plant materials used for RNA extraction were 10-588
20 siliques at each developmental stage for each genotype. Concentrations of the RNA samples 589
were quantified by a NanoDrop 2000C spectrophotometer (Thermo Fisher Scientific). For cDNA 590
synthesis, a total of 1 μg RNA from each sample was first treated with DNase I to eliminate 591
genomic DNA contamination, and then used as a template for reverse transcription (QuantiTect® 592
Reverse Transcription Kit, QIAGEN). The cDNA samples were used as templates for 593
polymerase chain reactions (PCR) or quantitative qPCR. The primers for the PCR or qPCR are 594
listed in Table S3. The qPCR was performed with the QuantiTect® SYBR® Green PCR Kit 595
(QIAGEN) using the CFX96 Touch™ Real-Time PCR Detection System (Bio-Rad Laboratories, 596
Hercules, California, USA) or LightCycler® 480 Real-Time PCR System (Roche, Indianapolis, 597
Indiana, USA), with three biological replicates and nine technical replicates for each sample type 598
and ACTIN2 as the internal control. Primers for ACTIN2 are GTCGTACAACCGGTATTGTG-3 599
and GAGCTGGTCTTTGAGGTTTC. 600
601
Confirmation of T-DNA Insertion Mutants and Generation of Mutant Combinations 602
603
Homozygous T-DNA insertion mutants were confirmed using PCR with gene-specific and T-604
DNA primers (Table S3) and the PCR Master Mix Kit (QIAGEN). Genomic DNA samples used 605
in the PCR were isolated according to Murray and Thompson (1980). PCR products were also 606
sequenced to confirm the DNA insertion sites in each mutant. Antibiotic selections of transgenic 607
lines were also employed to check the homozygosity of T-DNA insertion mutants, with 608
kanamycin for the SALK lines, Basta for the SAIL line, hygromycin B for the WiscDsLox line, 609
and sulfadiazine for the GABI-Kat line. The man-7-3 mutant was confirmed with GUS staining 610
of its flowers. 611
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21
612
Plasmid Construction and Transformation 613
614
The promoters of CEL6 (1956 bp) and MAN7 (857 bp) were first cloned into the pMD19-T 615
vector (Clontech, Mountain View, California, USA) to create pMD19T-pCEL6 and pMD19T-616
pMAN7. These promoter fragments were used to replace the CMV 35S promoter in the 617
pCAMBIA-1305.1 vector to create the pCEL6:GUS and pMAN7:GUS gene constructs. The same 618
promoter fragments and their corresponding cDNA fragments were combined using the In-619
Fusion Cloning Kit (Clontech, Mountain View, California, USA), and the newly created 620
fragments were used to replace the 35S promoter in the pCAMBIA-1305.1 vector to create 621
pCEL6:CEL6-GUS and pCAMBIA-pMAN7:MAN7-GUS, respectively. For overexpression of 622
CEL6 and MAN7, each of their genomic coding regions was first cloned as two separate 623
fragments into pMD19-T to circumvent the TA-cloning size limit. The two fragments were then 624
combined using the In-fusion cloning system to form the full-length coding region of each gene 625
in the pCAMBIA-1305.1 vector to create the pCAMBIA-OECEL6 and pCAMBIA-OEMAN7 626
gene constructs. The primers used in all of the cloning steps are listed in Table S4. Completed 627
plasmids were sequenced to ensure that the plasmids were correct. Agrobacterium cells with a 628
binary vector system including one of these plasmids were used to transform Col-0 plants 629
(Clough and Bent, 1998). Transformants were selected on agar plates containing 15 mg/L 630
hygromycin B (AG Scientific, San Diego, California, USA). 631
632
GUS staining 633
634
Seedlings, inflorescences, and siliques were incubated overnight in GUS staining solution that 635
contained 10 mM EDTA, 0.1% (v/v) Triton X-100, 100 µg/ml chloramphenicol, 2 mg/ml 5-636
Bromo-4-chloro-3-indoxyl-β-D-glucuronide (X-Gluc), 0.5 mM ferric cyanide, and 0.5 mM 637
ferrous cyanide in 50 mM sodium phosphate buffer (pH = 7.0). The samples were cleared several 638
times in 70% ethanol. Six or more independent lines for each transgene showed similar GUS 639
staining patterns, and one of them is shown in Fig. 2 and Fig. S3-7. 640
641
TUNEL assay 642
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22
643
Small segments of siliques were fixed in 4% (w/v) paraformaldehyde in 0.1 M phosphate-644
buffered solution (PBS) overnight at 4℃, followed by three washes (15 minutes each) in the 645
same buffer. Specimens were dehydrated in a graded ethanol series (15%, 30%, 45%, 60%, 70%, 646
80%, 90%, 100%) and washed two times (20 minutes each) in dimethyl benzene, and infiltrated 647
and embedded in Paraffin. Paraffin sections of 5-7 μm were cut using a rotary microtome 648
(American Optical, USA). The TUNEL assay was performed on these sections using the 649
DeadEnd Fluorometric TUNEL System (Promega, Madison, WI, USA) according to the 650
manufacturer’s instructions. Slides were then immediately stained with 10 μg/mL propidium 651
iodide (Sigma-Aldrich, St. Louis, MO, USA) and mounted with SlowFade Gold antifade reagent 652
(Invitrogen). Samples were observed and photographed under a Leica DM6 B microscope 653
equipped with the Leica DFC550 imaging system (Deng et al., 2014). 654
655
Light Microscopy and Transmission Electron Microscopy for Other Morphological Studies 656
657
For sections for both light and transmission electron microscopy, fresh siliques were first 658
embedded in 1% (w/v) agarose and quickly cut into small segments using a razor blade. Agarose 659
embedding helped maintain the relative positions of the valves and the replum of a dehiscent or 660
nearly dehiscent silique in subsequent tissue processing steps. The small segments of siliques 661
were then fixed in 4% (w/v) paraformaldehyde and 3% (w/v) glutaraldehyde in 0.1 M phosphate-662
buffered solution (PBS) overnight at 4℃, followed by three washes (15 minutes each) in the 663
same buffer. Samples were then post-fixed in 1% (w/v) osmium tetroxide in PBS for 2 h at room 664
temperature (25℃), followed by three washes (15 minutes each) in PBS. Specimens were 665
dehydrated in a graded ethanol series (15%, 30%, 45%, 60%, 70%, 80%, 90%, 100%) and 666
washed two times (10 minutes each time) in propylene oxide, and infiltrated and embedded in 667
Epon 812 (SPI Supplies Division of Structure Probe Inc., USA). Polymerization proceeded for 668
24 h at 40℃, followed by 24 h at 60℃. For light microscopy, specimens were cut into 1-2 μm-669
thick sections using glass knives through Leica EM UC6 ultra-microtome (Leica, Germany), and 670
stained with Toluidine Blue O. Similarly, 1-2 μm-thick sections of GUS-stained siliques were 671
prepared after dehydration in a graded ethanol series starting from 70% ethanol without 672
histological staining. For transmission electron microscopy, 70–90 nm-thick sections of the same 673
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23
embedded specimens were cut using a diamond knife (Diatome, Switzerland) on a Leica EM 674
UC6 ultramicrotome, and collected by 150-mesh cuprum grids. Ultrathin sections were stained 675
with uranyl acetate and lead citrate. 676
Light microscopes used for observation and photographing were a Leica S6D dissecting 677
microscope equipped with the Leica EC3 imaging system (Leica, Wetzlar, Germany), a Leica 678
DMLB microscope equipped with the Leica DFC320 imaging system, and a Nikon Elipse 80i 679
microscope equipped with the Nikon DS-Ri1 imaging system (Melville, New York, New York, 680
USA). The transmission electron microscope used was a Philips FEI-Tecnai 12 (FEI, Eindhoven, 681
Netherlands). 682
683
Characterization of Duration of Silique Development and Dehiscence 684
685
To investigate the duration between stage15 and stage-18 siliques, at least 50 stage-15 flowers 686
from four or more plants per genotype were labeled with colored strings and followed to stage 18. 687
The long and short axes and areas of 50 cells in the separation layer in the transmission electron 688
microscopy images were measured using SigmaScan Pro 5 (Systat Software, San Jose, 689
California, USA) for each genotype. To determine the dehiscence rate, 15 pairs of consecutive 690
siliques per plant and six or more plants per genotype were examined. The younger silique of the 691
pair was yellow but still hydrated without an obviously dehiscent appearance to the naked eye. 692
Silique dehiscence status was determined either by the naked eye if the dehiscence was apparent 693
or under a dissecting microscope if otherwise. The dehiscence rate is expressed as a percentage 694
of the dehiscent siliques of all the siliques examined. To further compare the dehiscence abilities 695
of the genotypes that did not or largely did not naturally undergo dehiscence, a centrifugal force 696
was first applied to dry siliques of these genotypes, and then the siliques were examined under a 697
dissecting microscope. Individual dry siliques in 1.5 ml microcentrifuge tubes were spun at 698
18000 g for 1 minute in a centrifuge (Eppendorf 5414D). For each genotype, six sets of 10 699
siliques per set were centrifuged. Statistical analysis (t-test) was conducted in Microsoft Excel 700
with 2 tails and unequal variance. The standard errors of the samples were calculated in 701
SigmaScan Pro 5. 702
703
Supplemental Data 704
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24
Figure S1. Examples of siliques of Col-0 at stages 17-19. 705
Figure S2. Relative expression of IND and ALC in Col-0 and their respective mutants in stage-706
17 siliques (10D). 707
Figure S3. GUS signals in vegetative and floral organs in pCEL6: GUS plants. 708
Figure S4. GUS signals in stages 15-17 siliques. 709
Figure S5. GUS signals in vegetative and floral organs in pMAN7: GUS plants. 710
Figure S6. GUS signals in vegetative and floral organs in pCEL6:CEL6-GUS plants. 711
Figure S7. GUS signals in vegetative and floral organs in pMAN7:MAN7-GUS plants. 712
Figure S8. GUS signals in semi-thin sections of stage-17B (12D) siliques. 713
Figure S9. Confirmation of the cel6 and man7 mutant alleles by PCR. 714
Figure S10. Transmission electron microscopy images of transverse sections of early and late 715
stage-17 siliques. 716
Figure S11. TUNEL signals at stages not shown in Fig. 5. 717
Figure S12. Col-0 siliques as representatives of the younger siliques used in the dehiscence rate 718
investigation. 719
Figure S13. CEL6 or MAN7 expression levels and silique dehiscence rates in CEL6- and MAN7-720
overexpression lines. 721
Table S1. Thirty-nine cellulase and other cell-wall degrading enzyme genes identified by in 722
silico searches. 723
Table S2. Twelve cellulase and other cell-wall degrading enzyme genes with a relative 724
expression level > 1 in stage-17 siliques according to searches with AtGenExpress Visualization 725
Tool. 726
Table S3. Primers for RT-PCR, qPCR, and T-DNA insertion identification. 727
Table S4. Primers for gene cloning. 728
729
ACKNOWLEDGEMENTS 730
731
The authors thank Yixing Wang at Oklahoma State University and Lizhen Tao at South China 732
Agricultural University for help on molecular experiments. The authors also thank Yaoguang Liu 733
at South China Agricultural University for providing the vectors used in this investigation. 734
735
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25
736
FIGURE LEGENDS 737
738
Figure 1. RT-qPCR analysis of CEL6 and MAN7 expression in siliques of Col-0 and the ind-7 739
and alc-3 mutants. 740
741
(A) CEL6 expression at different developmental stages of Col-0. 742
(B) MAN7 expression at different developmental stages of Col-0. 743
(C) CEL6 expression at stage 17B in Col-0 and the ind-7 and alc-3 mutant. 744
(D) MAN7 expression at stage 17B in Col-0 and the ind-7 and alc-3 mutant. 745
6D-12D in (A) and (B) and similar designations in subsequent figures denote the number of days 746
after anthesis. Shown in each plot are average relative expression levels ± standard errors with 747
the value of the first bar on the left being 1. 748
749
Figure 2. GUS staining patterns in siliques of the GUS-promoter and GUS-protein fusion lines 750
of the CEL6 and MAN7 genes in the wild-type, ind-7, and alc-3 backgrounds. 751
752
(A) and (B) Siliques of a pCEL6:GUS line. 753
(C) and (D) Silique of a pCEL6:CEL6-GUS line. 754
(E) and (F) Silique of a pCEL6:GUS line in the ind-7 mutant background. 755
(G) and (H) Silique of a pCEL6:GUS line in the alc-3 mutant background. 756
(I) and (J) Silique of a pMAN7:GUS line. 757
(K) and (L) Silique of a pMAN7:MAN7-GUS line. 758
(M) and (N) Silique of a pMAN7:GUS line in the ind-7 mutant background. 759
(O) and (P) Silique of a pMAN7:GUS line in the alc-3 mutant background. 760
(B), (D), (F), (H), (J), (L), (N), and (P) Higher magnification images of the rectangular areas in 761
the images immediately to the left, respectively. Red arrows indicate funiculi. In dehisced 762
siliques (B, D, and J), vertically aligned red dots delineate the replum (right two dotted lines in B 763
or two central dotted lines in D and J) and mark the freed valve margins. In non-dehisced 764
siliques (F, H, L, N, and P), the dotted lines mark the junction areas between the valves and the 765
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26
replum. Bar in (A) = 500 μm for (A), (C), (E), (G), (I), (K), (M), and (O). Bar in (B) = 100 μm 766
for (B), (D), (F), (H), (J), (L), (N), and (P). 767
768
Figure 3. Identification of the cel6-1, cel6-2, man7-1, and man7-3 mutants. 769
770
(A) Positions of the T-DNA insertions in At4g39010 (CEL6) and At5g66460 (MAN7). Black 771
boxes and the lines between them represent exons and introns, respectively. Open boxes 772
represent the predicted 5- and 3-untranslated regions. Triangles indicate the positions of the T-773
DNA insertions. 774
(B) Average relative expression levels (± standard errors) of CEL6 in stage-17 siliques of Col-0 775
and the cel6-1 and cel6-2 mutants. The Col-0 expression level is defined as 1. 776
(C) Average relative expression levels (± standard errors) of MAN7 in stage-17 siliques of Col-0 777
and the man7-1 and man7-3 mutants. The Col-0 expression level is defined as 1. 778
779
Figure 4. Transmission electron microscopy images of transverse sections of stage-17 siliques of 780
Col-0 and the cel6 and man7 mutants. 781
782
(A1), (B1), (C1), and (D1) Col-0. 783
(A2), (B2), (C2), and (D2) The cel6-1 mutant. 784
(A3), (B3), (C3), and (D3) The cel6-2 mutant. 785
(A4), (B4), (C4), and (D4) The man7-1 mutant. 786
(A5), (B5), (C5), and (D5) The man7-3 mutant. 787
(A6), (B6), (C6), and (D6) The cel6-1 man7-3 double mutant. 788
(A1-6) Siliques at stage 4D (4 days after anthesis). 789
(B1-6) Siliques at stage 6D. 790
(C1-6) Siliques at stage 8D. 791
(D1-6) Siliques at stage 10D. 792
Red stars in Col-0 indicate lignified cells, and in the mutants either cells presumably destined to 793
be lignified or lignified cells, in the dehiscence zone. Bar = 10 μm for all images. 794
795
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27
Figure 5. TUNEL signals in silique cross sections of Col-0 and the cel6-1, cel6-2, man7-1, and 796
man7-3 mutants. 797
798
All images are merged TUNEL (green) and PI (red; nuclear stain) fluorescence images, except 799
for (C), (G), (K), (O), and (S), which are bright-field images corresponding to images 800
immediately to the left, respectively. Insets show enlargements of the rectangular areas marked 801
in the corresponding images. Bar in the inset in (B) = 5 µm for all the insets, and bar in (A) = 50 802
μm all the other images. 803
804
Figure 6. Silique phenotypes in Col-0 and the cel6 and man7 mutants. 805
806
(A) Average ratios (± standard errors) of long axis to short axis of cells in the separation layer. 807
(B) Average cell areas (± standard errors) of cells in the separation layer. 808
(C) Average dehiscence rates (± standard errors) of two consecutive siliques during the stage 809
18B-19A transition. Black bars are of the younger siliques and open bars of the older siliques. 810
DR-average dehiscence rate. 811
812
Figure 7. Transmission electron microscopy images of transverse sections of stage-17B-to-813
stage-18 siliques of Col-0 and the cel6 and man7 mutants. 814
815
(A1), (B1), and (C1) Col-0. 816
(A2), (B2), and (C2) The cel6-1 mutant. 817
(A3), (B3), and (C3) The cel6-2 mutant. 818
(A4), (B4), and (C4) The man7-1 mutant. 819
(A5), (B5), and (C5) The man7-3 mutant. 820
(A6), (B6), and (C6) The cel6-1 man7-3 double mutant. 821
(A1-6) Siliques at stage 17B (12D). 822
(B1-6) Siliques at stage 18A. 823
(C1-6) Siliques at stage 18B. 824
Red stars indicate lignified cells in the dehiscence zone. Blue triangles indicate presumed 825
separation layer cells. Arrows in Col-0 indicate degenerating cells or wall stubs from 826
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28
degenerated cells in the separation layer, and arrows in the mutants indicate intact separation 827
layer cells. Bar = 10 μm for all images. 828
829
Figure 8. Transmission electron microscopy images of transverse sections of stage-18B siliques 830
in single, double, triple, and quadruple mutants. 831
832
(A) The adpg1-1 mutant. 833
(B) The cel6-1 adpg1-1 double mutant. 834
(C) The man7-3 adpg1-1 double mutant. 835
(D) The cel6-1 man7-3 adpg1-1 triple mutant. 836
(E) The adpg2-1 mutant. 837
(F) The cel6-1 adpg2-1 double mutant. 838
(G) The man7-3 adpg2-1 double mutant. 839
(H) The cel6-1 man7-3 adpg2-1 triple mutant. 840
(I) The adpg1-1 adpg2-1 double mutant. 841
(J) The cel6-1 adpg1-1 adpg2-1 triple mutant. 842
(K) The man7-3 adpg1-1 adpg2-1 triple mutant. 843
(L) The cel6-1 man7-3 adpg1-1 adpg2-1 quadruple mutant. 844
Red stars indicate lignified cells in the dehiscence zone. Blue triangles indicate presumed broken 845
or intact separation layer cells. Bar = 10 μm for all images. 846
847
Figure 9. Average dehiscence rates (± standard errors) in the single, double, triple, and 848
quadruple mutants. 849
850
(A) During the stage 18B-19A transition. Black bars are of the younger siliques and open bars of 851
the older siliques. 852
(B) Stage-19A siliques of naturally indehiscent or nearly indehiscent genotypes after the 853
centrifugation impact. 854
DR-average dehiscence rate. 855
856
LITERATURE CITED 857
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
29
858
Abeles, F.B. (1969). Abscission: role of cellulase. Plant Physiol. 44: 447-452. 859
Bar-Dror, T., Dermastia, M., Kladnik, A., Znidaric, M.T., Novak, M.P., Meir, S., Burd, S., 860
Philosoph-Hadas, S., Ori, N., Sonego, L., Dickman, M.B., and Lers, A. (2011). Programmed 861
cell death occurs asymmetrically during abscission in tomato. Plant Cell. 23: 4146-4163. 862
Bensoussan, L., Moraïs, S., Dassa, B., Friedman, N., Henrissat, B., Lombard, V., Bayer, E.A., 863
and Mizrahi, I. (2017). Broad phylogeny and functionality of cellulosomal components in the 864
bovine rumen microbiome. Environ Microbiol. 19: 185-197. 865
Brummell, D.A., Bird, C.R., Schuch, W., and Bennett, A.B. (1997). An endo-1,4-beta-glucanase 866
expressed at high levels in rapidly expanding tissues. Plant Mol Biol. 33: 87-95. 867
Christoffersen, R.E., Tucker, M.L., and Laties, G.G. (1984). Cellulase gene expression in 868
ripening avocado fruit: The accumulation of cellulase mRNA and protein as demonstrated by 869
cDNA hybridization and immunodetection. Plant Mol Biol. 3: 385-91. 870
Clough, S.J., and Bent, A.F. (1998). Floral dip: A simplified method for Agrobacterium-871
mediated transformation of Arabidopsis thaliana. Plant J. 16: 735-743. 872
del Campillo, E., and Bennett, A.B. (1996). Pedicel breakstrength and cellulase gene expression 873
during tomato flower abscission. Plant Physiol. 111: 813-820. 874
del Campillo, E., Abdel-Aziz, A., Crawford, D., and Patterson, S.E. (2004). Root cap specific 875
expression of an endo-beta-1,4-D-glucanase (cellulase): a new marker to study root 876
development in Arabidopsis. Plant Mol Biol. 56: 309-323. 877
Deng, Y.T., Zou, W.X., Li, G., and Zhao, J. (2014). TRANSLOCASE OF THE INNER 878
MEMBRANE9 and 10 are essential for maintaining mitochondrial function during early 879
embryo cell and endosperm free nucleus divisions in Arabidopsis. Plant Physiol. 166: 853-868. 880
Dollhofer, V., Podmirseg, S.M., Callaghan, T.M., Griffith, G.W., and Fliegerová, K. (2015). 881
Anaerobic fungi and their potential for biogas production. Adv Biochem Eng Biotechnol. 151: 882
41-61. 883
Du, M., Li, Y., Tian, X., Duan, L., Zhang, M., Tan, W., Xu, D., and Li, Z. (2014). The 884
phytotoxin coronatine induces abscission-related gene expression and boll ripening during 885
defoliation of cotton. PLoS One. 9: e97652. 886
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
30
Fabi, J.P., Broetto, S.G., da Silva, S.L., Zhong, S., Lajolo, F.M., and do Nascimento, J.R. (2014). 887
Analysis of papaya cell wall-related genes during fruit ripening indicates a central role of 888
polygalacturonases during pulp softening. PLoS One. 9: e105685. 889
García-Gago, J.A., Posé, S., Muñoz-Blanco, J., Quesada, M.A., and Mercado, J.A. (2009). 890
The polygalacturonase FaPG1 gene plays a key role in strawberry fruit softening. Plant Signal 891
Behav. 4: 766-768. 892
Gonzalez-Bosch, C., del Campillo, E., and Bennett, A.B. (1997). Immunodetection and 893
characterization of tomato endo-beta-1,4-glucanase Cel1 protein in flower abscission zones. 894
Plant Physiol. 114: 1541-1546. 895
González-Carranza, Z.H., Elliott, K.A., and Roberts, J.A. (2007). Expression of 896
polygalacturonases and evidence to support their role during cell separation processes in 897
Arabidopsis thaliana. J Exp Bot. 58: 3719-3730. 898
Gorguet, B., Schipper, D., van Lammeren, A., Visser, R.G., and van Heusden, A.W. (2009). ps-899
2, the gene responsible for functional sterility in tomato, due to non-dehiscent anthers, is the 900
result of a mutation in a novel polygalacturonase gene. Theor Appl Genet. 118: 1199-1209. 901
Harpster, M.H., Lee, K.Y., and Dunsmuir, P. (1997). Isolation and characterization of a gene 902
encoding endo-beta-1,4-glucanase from pepper (Capsicum annuum L.). Plant Mol Biol. 33: 47-903
59. 904
Heredia, A, Jiménez, A, and Guillén, R. (1995). Composition of plant cell walls. Z Lebensm 905
Unters Forsch. 200: 24-31. 906
His, I., Driouich, A., Nicol, F., Jauneau, A., and Höfte, H. (2001). Altered pectin composition in 907
primary cell walls of korrigan, a dwarf mutant of Arabidopsis deficient in a membrane-bound 908
endo-1,4-beta-glucanase. Planta. 212: 348-358. 909
Iglesias-Fernández, R., Rodríguez-Gacio, M.C., Barrero-Sicilia, C., Carbonero, P., and Matilla, 910
A. (2011). Three endo-β-mannanase genes expressed in the micropylar endosperm and in the 911
radicle influence germination of Arabidopsis thaliana seeds. Planta. 233: 25-36. 912
Iglesias-Fernández, R., Barrero-Sicilia, C., Carrillo-Barral, N., Oñate-Sánchez, L., and 913
Carbonero, P. (2013). Arabidopsis thaliana bZIP44: a transcription factor affecting seed 914
germination and expression of the mannanase-encoding gene AtMAN7. Plant J. 74: 767-780. 915
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
31
Jenkins, E.S., Paul, W., Craze, M., Whitelaw, C.A., Weigand, A., and Roberts, J.A. (1999). 916
Dehiscence-related expression of an Arabidopsis thaliana gene encoding a polygalacturonase 917
in transgenic plants of Brassica napus. Plant Cell Environ. 22: 159-167. 918
Keegstra, K. (2010). Plant Cell Walls. Plant Physiol. 154: 483-486. 919
Lane, D.R., Wiedemeier, A., Peng, L., Höfte, H., Vernhettes, S., Desprez, T., Hocart, 920
C.H., Birch, R.J., Baskin, T.I., Burn, J.E., Arioli, T., Betzner, A.S., and Williamson, R.E. 921
(2001). Temperature-sensitive alleles of RSW2 link the KORRIGAN endo-1,4-beta-glucanase 922
to cellulose synthesis and cytokinesis in Arabidopsis. Plant Physiol. 126: 278-288. 923
Lashbrook, C.C., Gonzalez-Bosch, C., and Bennett, A.B. (1994). Two divergent endo-beta-1,4-924
glucanase genes exhibit overlapping expression in ripening fruit and abscising flowers. Plant 925
Cell. 6: 1485-1493. 926
Le, B.H., Cheng, C., Bui, A.Q., Wagmaister, J.A., Henry, K.F., Pelletier, J., Kwong, L., 927
Belmonte, M., Kirkbride, R., Horvath, S., Drews, G.N., Fischer, R.L., Okamuro, J.K., Harada, 928
J.J., and Goldberg, R.B. (2010). Global analysis of gene activity during Arabidopsis seed 929
development and identification of seed-specific transcription factors. Proc Natl Acad Sci USA. 930
107: 8063-8070. 931
Liljegren, S.J., Roeder, A.H., Kempin, S.A., Gremski, K., Østergaard, L., Guimil, S., Reyes, 932
D.K., and Yanofsky, M.F. (2004). Control of fruit patterning in Arabidopsis by 933
INDEHISCENT. Cell. 116: 843-853. 934
Martínez-Andújar, C., Pluskota, W.E., Bassel, G.W., Asahina, M., Pupel, P., Nguyen, T.T., 935
Takeda-Kamiya, N., Toubiana, D., Bai, B., Górecki, R.J., Fait, A., Yamaguchi, S., and 936
Nonogaki, H. (2012). Mechanisms of hormonal regulation of endosperm cap-specific gene 937
expression in tomato seeds. Plant J. 71: 575-586. 938
Murray, M.G., and Thompson, W.F. (1980). Rapid isolation of high molecular weight plant 939
DNA. Nucleic Acids Res. 8: 4321-4325. 940
Nakano, T., Kato, H., Shima, Y., and Ito, Y. (2015). Apple SVP family MADS-box proteins and 941
the tomato pedicel abscission zone regulator JOINTLESS have similar molecular activities. 942
Plant Cell Physiol. 56: 1097-1106. 943
Nakashima, J., Endo, S., and Fukuda, H. (2004). Immunocytochemical localization of 944
polygalacturonase during tracheary element differentiation in Zinnia elegans. Planta. 218: 729-945
739. 946
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
32
Nicol, F., His, I., Jauneau, A., Vernhettes, S., Canut, H., and Höfte, H. (1998). A plasma 947
membrane-bound putative endo-1,4-beta-D-glucanase is required for normal wall assembly 948
and cell elongation in Arabidopsis. EMBO J. 17: 5563-5576. 949
Ogawa, M., Kay, P., Wilson, S., and Swain S.M. (2009). ARABIDOPSIS DEHISCENCE ZONE 950
POLYGALACTURONASE1 (ADPG1), ADPG2, and QUARTET2 are polygalacturonases 951
required for cell separation during reproductive development in Arabidopsis. Plant Cell. 21: 952
216–233. 953
Petersen, M., Sander, L., Child, R., van Onckelen, H., Ulvskov, P., and Borkhardt, B. (1996). 954
Isolation and characterisation of a pod dehiscence zone-specific polygalacturonase from 955
Brassica napus. Plant Mol Biol. 31: 517-527. 956
Rajani, S., and Sundaresan, V. (2001). The Arabidopsis myc/bHLH gene ALCATRAZ enables 957
cell separation in fruit dehiscence. Curr Biol. 11: 1914-1922. 958
Roongsattham, P., Morcillo, F., Jantasuriyarat, C., Pizot, M., Moussu, S., Jayaweera, D., Collin, 959
M., Gonzalez-Carranza, Z.H., Amblard, P., Tregear, J.W., Tragoonrung, S., Verdeil, J.L., and 960
Tranbarger, T.J. (2012). Temporal and spatial expression of polygalacturonase gene family 961
members reveals divergent regulation during fleshy fruit ripening and abscission in the 962
monocot species oil palm. BMC Plant Biol. 12: 150. 963
Sander, L., Child, R., Ulvskov, P., Albrechtsen, M., and Borkhardt, B. (2001). Analysis of a 964
dehiscence zone endo-polygalacturonase in oilseed rape (Brassica napus) and Arabidopsis 965
thaliana: evidence for roles in cell separation in dehiscence and abscission zones, and in stylar 966
tissues during pollen tube growth. Plant Mol Biol. 46: 469-479. 967
Sanders, P.M., Lee, P.Y., Biesgen, C., Boone, J.D., Beals, T.P., Weiler, E.W., and Goldberg. 968
R.B. (2000). The ARABIDOPSIS DELAYED DEHISCENCE1 gene encodes an enzyme in the 969
jasmonic acid synthesis pathway. Plant Cell. 12: 1041-1061. 970
Shani, Z., Dekel, M., Tsabary, G., and Shoseyov, O. (1997). Cloning and characterization of 971
elongation specific endo-1,4-beta-glucanase (cel1) from Arabidopsis thaliana. Plant Mol Biol. 972
34: 837-842. 973
Sitrit, Y., Hadfield, K.A., Bennett, A.B., Bradford, K.J., and Downie, A.B. (1999). Expression of 974
a polygalacturonase associated with tomato seed germination. Plant Physiol. 121: 419-428. 975
Smyth, D.R., Bowman, J.L., and Meyerowitz, E.M. (1990). Early flower development in 976
Arabidopsis. Plant Cell. 2: 755-767. 977
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
33
Trainotti, L., Spolaore, S., Ferrarese, L., and Casadoro, G. (1997). Characterization of ppEG1, a 978
member of a multigene family which encodes endo-beta-1,4-glucanase in peach. Plant Mol 979
Biol. 34: 791-802. 980
van Doorn, W.G., Beers, E.P., Dangl, J.L., Franklin-Tong, V.E., Gallois, P., Hara-Nishimura, I., 981
Jones, A.M., Kawai-Yamada, M., Lam, E., Mundy, J., Mur, L.A., Petersen, M., Smertenko, A., 982
Taliansky, M., Van Breusegem, F., Wolpert, T., Woltering, E., Zhivotovsky, B., and Bozhkov, 983
P.V. (2011). Morphological classification of plant cell deaths. Cell Death Differ. 18: 1241-984
1246. 985
van Gelderen, K., van Rongen, M.., Liu, A., Otten, A., and Offringa, R. (2016). An 986
INDEHISCENT-controlled auxin response specifies the separation layer in early Arabidopsis 987
Fruit. Mol Plant. 9: 857-869. 988
Vanyushin, B.F., Bakeeva, L.E., Zamyatnina, V.A., and Aleksandrushkina, N.I. (2004). 989
Apoptosis in plants: specific features of plant apoptotic cells and effect of various factors and 990
agents. Int Rev Cytol. 233: 135-79. 991
Urbanowicz, B.R., Bennett, A.B., Del Campillo, E., Catalá, C., Hayashi, T., Henrissat, B., Höfte, 992
H., McQueen-Mason, S.J., Patterson, S.E., Shoseyov, O., Teeri, T.T., and Rose, J.K. (2007). 993
Structural organization and a standardized nomenclature for plant endo-1,4-beta-glucanases 994
(cellulases) of glycosyl hydrolase family 9. Plant Physiol. 144: 1693-1696. 995
Wu, H., Mori, A., Wang, Y., and Yang, M. (2006). The INDEHECIENT protein regulates unequal cell 996
divisions in Arabidopsis fruit. Planta. 224: 971-979. 997
Yu, L., Sun, J., and Li, L. (2013). PtrCel9A6, an endo-1,4-β-glucanase, is required for cell 998
wall formation during xylem differentiation in Populus. Mol Plant. 6: 1904-1917. 999
Yu, L., Chen, H., Sun, J., and Li, L. (2014). PtrKOR1 is required for secondary cell 1000
wall cellulose biosynthesis in Populus. Tree Physiol. 34: 1289-1300. 1001
Yuan, J.S., Yang, X., Lai, J., Lin, H., Cheng, Z.M., Nonogaki, H., and Chen, F. (2007). The 1002
endo-beta-mannanase gene families in Arabidopsis, rice, and poplar. Funct Integr Genomics. 7: 1003
1-16. 1004
Yung, M.H., Schaffer, R., and Putterill, J. (1999). Identification of genes expressed during early 1005
Arabidopsis carpel development by mRNA differential display: characterisation of ATCEL2, a 1006
novel endo-1,4-beta-D-glucanase gene. Plant J. 17: 203-208. 1007
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Parsed CitationsAbeles, F.B. (1969). Abscission: role of cellulase. Plant Physiol. 44: 447-452.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Bar-Dror, T., Dermastia, M., Kladnik, A., Znidaric, M.T., Novak, M.P., Meir, S., Burd, S., Philosoph-Hadas, S., Ori, N., Sonego, L.,Dickman, M.B., and Lers, A. (2011). Programmed cell death occurs asymmetrically during abscission in tomato. Plant Cell. 23: 4146-4163.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Bensoussan, L., Moraïs, S., Dassa, B., Friedman, N., Henrissat, B., Lombard, V., Bayer, E.A., and Mizrahi, I. (2017). Broad phylogeny andfunctionality of cellulosomal components in the bovine rumen microbiome. Environ Microbiol. 19: 185-197.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Brummell, D.A., Bird, C.R., Schuch, W., and Bennett, A.B. (1997). An endo-1,4-beta-glucanase expressed at high levels in rapidlyexpanding tissues. Plant Mol Biol. 33: 87-95.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Christoffersen, R.E., Tucker, M.L., and Laties, G.G. (1984). Cellulase gene expression in ripening avocado fruit: The accumulation ofcellulase mRNA and protein as demonstrated by cDNA hybridization and immunodetection. Plant Mol Biol. 3: 385-91.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Clough, S.J., and Bent, A.F. (1998). Floral dip: A simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana.Plant J. 16: 735-743.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
del Campillo, E., and Bennett, A.B. (1996). Pedicel breakstrength and cellulase gene expression during tomato flower abscission. PlantPhysiol. 111: 813-820.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
del Campillo, E., Abdel-Aziz, A., Crawford, D., and Patterson, S.E. (2004). Root cap specific expression of an endo-beta-1,4-D-glucanase(cellulase): a new marker to study root development in Arabidopsis. Plant Mol Biol. 56: 309-323.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Deng, Y.T., Zou, W.X., Li, G., and Zhao, J. (2014). TRANSLOCASE OF THE INNER MEMBRANE9 and 10 are essential for maintainingmitochondrial function during early embryo cell and endosperm free nucleus divisions in Arabidopsis. Plant Physiol. 166: 853-868.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Dollhofer, V., Podmirseg, S.M., Callaghan, T.M., Griffith, G.W., and Fliegerová, K. (2015). Anaerobic fungi and their potential for biogasproduction. Adv Biochem Eng Biotechnol. 151: 41-61.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Du, M., Li, Y., Tian, X., Duan, L., Zhang, M., Tan, W., Xu, D., and Li, Z. (2014). The phytotoxin coronatine induces abscission-related geneexpression and boll ripening during defoliation of cotton. PLoS One. 9: e97652.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Fabi, J.P., Broetto, S.G., da Silva, S.L., Zhong, S., Lajolo, F.M., and do Nascimento, J.R. (2014). Analysis of papaya cell wall-relatedgenes during fruit ripening indicates a central role of polygalacturonases during pulp softening. PLoS One. 9: e105685.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
García-Gago, J.A., Posé, S., Muñoz-Blanco, J., Quesada, M.A., and Mercado, J.A. (2009). The polygalacturonase FaPG1 gene plays a key www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from
Copyright © 2018 American Society of Plant Biologists. All rights reserved.
role in strawberry fruit softening. Plant Signal Behav. 4: 766-768.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Gonzalez-Bosch, C., del Campillo, E., and Bennett, A.B. (1997). Immunodetection and characterization of tomato endo-beta-1,4-glucanase Cel1 protein in flower abscission zones. Plant Physiol. 114: 1541-1546.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
González-Carranza, Z.H., Elliott, K.A., and Roberts, J.A. (2007). Expression of polygalacturonases and evidence to support their roleduring cell separation processes in Arabidopsis thaliana. J Exp Bot. 58: 3719-3730.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Gorguet, B., Schipper, D., van Lammeren, A., Visser, R.G., and van Heusden, A.W. (2009). ps-2, the gene responsible for functionalsterility in tomato, due to non-dehiscent anthers, is the result of a mutation in a novel polygalacturonase gene. Theor Appl Genet. 118:1199-1209.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Harpster, M.H., Lee, K.Y., and Dunsmuir, P. (1997). Isolation and characterization of a gene encoding endo-beta-1,4-glucanase frompepper (Capsicum annuum L.). Plant Mol Biol. 33: 47-59.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Heredia, A, Jiménez, A, and Guillén, R. (1995). Composition of plant cell walls. Z Lebensm Unters Forsch. 200: 24-31.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
His, I., Driouich, A., Nicol, F., Jauneau, A., and Höfte, H. (2001). Altered pectin composition in primary cell walls of korrigan, a dwarfmutant of Arabidopsis deficient in a membrane-bound endo-1,4-beta-glucanase. Planta. 212: 348-358.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Iglesias-Fernández, R., Rodríguez-Gacio, M.C., Barrero-Sicilia, C., Carbonero, P., and Matilla, A. (2011). Three endo-β-mannanasegenes expressed in the micropylar endosperm and in the radicle influence germination of Arabidopsis thaliana seeds. Planta. 233: 25-36.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Iglesias-Fernández, R., Barrero-Sicilia, C., Carrillo-Barral, N., Oñate-Sánchez, L., and Carbonero, P. (2013). Arabidopsis thaliana bZIP44:a transcription factor affecting seed germination and expression of the mannanase-encoding gene AtMAN7. Plant J. 74: 767-780.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Jenkins, E.S., Paul, W., Craze, M., Whitelaw, C.A., Weigand, A., and Roberts, J.A. (1999). Dehiscence-related expression of anArabidopsis thaliana gene encoding a polygalacturonase in transgenic plants of Brassica napus. Plant Cell Environ. 22: 159-167.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Keegstra, K. (2010). Plant Cell Walls. Plant Physiol. 154: 483-486.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Lane, D.R., Wiedemeier, A., Peng, L., Höfte, H., Vernhettes, S., Desprez, T., Hocart, C.H., Birch, R.J., Baskin, T.I., Burn, J.E., Arioli, T.,Betzner, A.S., and Williamson, R.E. (2001). Temperature-sensitive alleles of RSW2 link the KORRIGAN endo-1,4-beta-glucanase tocellulose synthesis and cytokinesis in Arabidopsis. Plant Physiol. 126: 278-288.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Lashbrook, C.C., Gonzalez-Bosch, C., and Bennett, A.B. (1994). Two divergent endo-beta-1,4-glucanase genes exhibit overlappingexpression in ripening fruit and abscising flowers. Plant Cell. 6: 1485-1493.
Pubmed: Author and Title www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
CrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Le, B.H., Cheng, C., Bui, A.Q., Wagmaister, J.A., Henry, K.F., Pelletier, J., Kwong, L., Belmonte, M., Kirkbride, R., Horvath, S., Drews,G.N., Fischer, R.L., Okamuro, J.K., Harada, J.J., and Goldberg, R.B. (2010). Global analysis of gene activity during Arabidopsis seeddevelopment and identification of seed-specific transcription factors. Proc Natl Acad Sci USA. 107: 8063-8070.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Liljegren, S.J., Roeder, A.H., Kempin, S.A., Gremski, K., Østergaard, L., Guimil, S., Reyes, D.K., and Yanofsky, M.F. (2004). Control offruit patterning in Arabidopsis by INDEHISCENT. Cell. 116: 843-853.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Martínez-Andújar, C., Pluskota, W.E., Bassel, G.W., Asahina, M., Pupel, P., Nguyen, T.T., Takeda-Kamiya, N., Toubiana, D., Bai, B.,Górecki, R.J., Fait, A., Yamaguchi, S., and Nonogaki, H. (2012). Mechanisms of hormonal regulation of endosperm cap-specific geneexpression in tomato seeds. Plant J. 71: 575-586.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Murray, M.G., and Thompson, W.F. (1980). Rapid isolation of high molecular weight plant DNA. Nucleic Acids Res. 8: 4321-4325.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Nakano, T., Kato, H., Shima, Y., and Ito, Y. (2015). Apple SVP family MADS-box proteins and the tomato pedicel abscission zoneregulator JOINTLESS have similar molecular activities. Plant Cell Physiol. 56: 1097-1106.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Nakashima, J., Endo, S., and Fukuda, H. (2004). Immunocytochemical localization of polygalacturonase during tracheary elementdifferentiation in Zinnia elegans. Planta. 218: 729-739.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Nicol, F., His, I., Jauneau, A., Vernhettes, S., Canut, H., and Höfte, H. (1998). A plasma membrane-bound putative endo-1,4-beta-D-glucanase is required for normal wall assembly and cell elongation in Arabidopsis. EMBO J. 17: 5563-5576.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Ogawa, M., Kay, P., Wilson, S., and Swain S.M. (2009). ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE1 (ADPG1), ADPG2,and QUARTET2 are polygalacturonases required for cell separation during reproductive development in Arabidopsis. Plant Cell. 21:216–233.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Petersen, M., Sander, L., Child, R., van Onckelen, H., Ulvskov, P., and Borkhardt, B. (1996). Isolation and characterisation of a poddehiscence zone-specific polygalacturonase from Brassica napus. Plant Mol Biol. 31: 517-527.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Rajani, S., and Sundaresan, V. (2001). The Arabidopsis myc/bHLH gene ALCATRAZ enables cell separation in fruit dehiscence. CurrBiol. 11: 1914-1922.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Roongsattham, P., Morcillo, F., Jantasuriyarat, C., Pizot, M., Moussu, S., Jayaweera, D., Collin, M., Gonzalez-Carranza, Z.H., Amblard, P.,Tregear, J.W., Tragoonrung, S., Verdeil, J.L., and Tranbarger, T.J. (2012). Temporal and spatial expression of polygalacturonase genefamily members reveals divergent regulation during fleshy fruit ripening and abscission in the monocot species oil palm. BMC PlantBiol. 12: 150.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Sander, L., Child, R., Ulvskov, P., Albrechtsen, M., and Borkhardt, B. (2001). Analysis of a dehiscence zone endo-polygalacturonase inoilseed rape (Brassica napus) and Arabidopsis thaliana: evidence for roles in cell separation in dehiscence and abscission zones, and
www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
in stylar tissues during pollen tube growth. Plant Mol Biol. 46: 469-479.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Sanders, P.M., Lee, P.Y., Biesgen, C., Boone, J.D., Beals, T.P., Weiler, E.W., and Goldberg. R.B. (2000). The ARABIDOPSIS DELAYEDDEHISCENCE1 gene encodes an enzyme in the jasmonic acid synthesis pathway. Plant Cell. 12: 1041-1061.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Shani, Z., Dekel, M., Tsabary, G., and Shoseyov, O. (1997). Cloning and characterization of elongation specific endo-1,4-beta-glucanase(cel1) from Arabidopsis thaliana. Plant Mol Biol. 34: 837-842. See comment in PubMed Commons below
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Sitrit, Y., Hadfield, K.A., Bennett, A.B., Bradford, K.J., and Downie, A.B. (1999). Expression of a polygalacturonase associated withtomato seed germination. Plant Physiol. 121: 419-428.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Smyth, D.R., Bowman, J.L., and Meyerowitz, E.M. (1990). Early flower development in Arabidopsis. Plant Cell. 2: 755-767.Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Trainotti, L., Spolaore, S., Ferrarese, L., and Casadoro, G. (1997). Characterization of ppEG1, a member of a multigene family whichencodes endo-beta-1,4-glucanase in peach. Plant Mol Biol. 34: 791-802.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
van Doorn, W.G., Beers, E.P., Dangl, J.L., Franklin-Tong, V.E., Gallois, P., Hara-Nishimura, I., Jones, A.M., Kawai-Yamada, M., Lam, E.,Mundy, J., Mur, L.A., Petersen, M., Smertenko, A., Taliansky, M., Van Breusegem, F., Wolpert, T., Woltering, E., Zhivotovsky, B., andBozhkov, P.V. (2011). Morphological classification of plant cell deaths. Cell Death Differ. 18: 1241-1246.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
van Gelderen, K., van Rongen, M.., Liu, A., Otten, A., and Offringa, R. (2016). An INDEHISCENT-controlled auxin response specifies theseparation layer in early Arabidopsis Fruit. Mol Plant. 9: 857-869.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Vanyushin, B.F., Bakeeva, L.E., Zamyatnina, V.A., and Aleksandrushkina, N.I. (2004). Apoptosis in plants: specific features of plantapoptotic cells and effect of various factors and agents. Int Rev Cytol. 233: 135-79.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Urbanowicz, B.R., Bennett, A.B., Del Campillo, E., Catalá, C., Hayashi, T., Henrissat, B., Höfte, H., McQueen-Mason, S.J., Patterson,S.E., Shoseyov, O., Teeri, T.T., and Rose, J.K. (2007). Structural organization and a standardized nomenclature for plant endo-1,4-beta-glucanases (cellulases) of glycosyl hydrolase family 9. Plant Physiol. 144: 1693-1696.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Wu, H., Mori, A., Wang, Y., and Yang, M. (2006). The INDEHECIENT protein regulates unequal cell divisions in Arabidopsis fruit. Planta.224: 971-979.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Yu, L., Sun, J., and Li, L. (2013). PtrCel9A6, an endo-1,4-β-glucanase, is required for cell wall formation during xylem differentiation inPopulus. Mol Plant. 6: 1904-1917.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Yu, L., Chen, H., Sun, J., and Li, L. (2014). PtrKOR1 is required for secondary cell wall cellulose biosynthesis in Populus. Tree Physiol.34: 1289-1300.
Pubmed: Author and Title www.plantphysiol.orgon June 17, 2020 - Published by Downloaded from Copyright © 2018 American Society of Plant Biologists. All rights reserved.
CrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Yuan, J.S., Yang, X., Lai, J., Lin, H., Cheng, Z.M., Nonogaki, H., and Chen, F. (2007). The endo-beta-mannanase gene families inArabidopsis, rice, and poplar. Funct Integr Genomics. 7: 1-16.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
Yung, M.H., Schaffer, R., and Putterill, J. (1999). Identification of genes expressed during early Arabidopsis carpel development bymRNA differential display: characterisation of ATCEL2, a novel endo-1,4-beta-D-glucanase gene. Plant J. 17: 203-208.
Pubmed: Author and TitleCrossRef: Author and TitleGoogle Scholar: Author Only Title Only Author and Title
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![REFERENCES - INFLIBNETshodhganga.inflibnet.ac.in/.../2683/16/16_references.pdf[49]. Agrahari S., Wadhwa N., “Isolation and characterization of Feather degrading enzymes from Bacillus](https://img.pdfslide.us/doc/110x75/5e9a43f235a6b6333f0d8d8c/references-49-agrahari-s-wadhwa-n-aoeisolation-and-characterization-of.jpg)
