Signalling Pathways of Auxin

8/13/2019 Signalling Pathways of Auxin

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The article was published in Journal: Biopolymers and cell, 2005, V. 21, N.1,

. 1!" # 21$ %&n 'uss.(.

)*N*T&+ N- *&)*N*T&+ +NT'/ /NT )'T N-

-*V*/3*NT. 3/*+4/')*N*T&+ +NT'/ 46&N

7&)N/7: T'N73&77&N N- '*/&8T&N

1 Victoriya . Tsy9ano;a, 1 /arysa . )alina, 2/udmila &. 3usateno, 2

' A?. 7&. &7. 74'p &dc@p &dc83p 6cp.p TI. genes of proteins(members of ubiuitin-protein ligase complex) and &64 genes of proteins (members of the

multi-subunit protein regulatory complex of &B"C signalosome) - components of the

ubiuitin;proteasome-mediated way degradation of Aux;IAA proteins repressing

transmission of auxin signals, The hypothetical model of regulation of gene expression by

the IAA is considered,

>ey words: the indole-3-acetic acid (IDD) receptors secondary messengers of IAA protein-

transporters of IAA auxin-regulated genes ubiuitin;proteasome-mediated way degradation

of protein-repressors of IAA,

&ntroduction. &uring the last fe' years considera(le )rogress has (een made in

the fundamental studies of )hytohormone (iosynthesis )ath'ays and their

molecular mechanisms* Physical+chemical techniues using radioactie isoto)e+

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la(elled -".,1/C, or 10N e2ogenous )hytohormones as standards as 'ell as

molecular genetic techniues ena(ling the identification of mutant genes, their

cloning, and further inestigation of these gene e2)ression )roducts -regulatory

)roteins )artici)ating in the transmission of signals of arious )hytohormone

classes 'ere used*

%he molecular mechanisms of )hysiological action of fie (asic)hytohormones classes3 au2ins, cytokinins, gi((erellins, ethylene, and a(scisic

acid are most inestigated )resently4 studies of the other hormone+like regulators

of )lant gro'th identified recently, e**, 5asmonates and (rassinosteroids, are also

)romising* No dou(t that it is of great interest t6 research the molecular

mechanisms of the interactions (et'een arious )hytohormone classes, forming

the )lant endogenous integral )hytohormonal system, 'hose e2istence has (een

)roed (y many e2)erimental data concerning (oth the narro'ly+s)ecific

)hytohormone effects and their cascade effects + )rocesses 'hen one hormone

induces the synthesis of the other hormones )roducing a s)ecific )hysiologicaleffect 71, "8*

%his fact has (een confirmed (y the results of many studies, 'hich hae

gien eidence that some increase in the adentie roots gro'th, as a result of

au2in and cytokinin effects, is caused (y the induction of the synthesis in cells of

1+aminocyclo)ro)an+1+car(o2ilate synthetase, inoled in the (iosynthesis of

ethylene, 'hich e2hi(its the a(oe mentioned )hysiological effect -e**,

stimulation of the adentie roots gro'th that is ty)ical for it 7/, $84 indole+/+

acetic acid -IAA and cytokinins inhi(it synthesis of each other, 'hile IAA

stimulates the ethylene synthesis 7184 au2in induces a )ost+translation )rocessing

of 9+2ylotransferase, an actie en:yme, limiting cytokinins synthesis 7084 the

)roducts of e2)ression of rol genes Agrobacterium rhizogenes modify the

gi((erellin meta(olism, (locking the actiity of gi((erellin+o2idase 70, ;8* %hus,

'ithout taking into account the hormone inter+influence, an unam(iguous

decision of uestion a(out s)ecificity of )hysiological action of each

)hytohormone is )ro(lematic -i*e* the cascade mechanism of )hytohormone

action ham)ers determination of mechanism of action each of them*

%he )hytohormones e2ecute im)ortant functions in coordinating )lant

gro'th and deelo)ment3 acting as chemical messengers during ontogenesis,

)hytohormones )artici)ate in controlling the organism


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In addition t6 the ma5or glyco)rotein ABP1, t'o more highly glycosylated

)oly)e)tides 'ith the molecular mass of3 "1 k&a -ma5or and "! k&a -minor

glyco)roteins 7"/ + "08 hae (een isolated electro)horetically and )urified from

coleo)tiles and mesocotiles of monocotyledonous )lants -corn, 'heat, and oats

using .P>C* %he follo'ing tendency has (een o(sered during the )lant

deelo)ment )eriod3 'ith an increase in si:e of coleo)tiles and mesocotiles, acorres)onding decrease in the au2in+(inding ca)acity and res)onse -elongation

t6 that )hytohormone occurs 710, ";8*

A differentiated intracellular and intratissue locali:ation of au2in rece)tors

has also (een studied on dicotyledonous )lants* Sus)ension and callus cultures of

to(acco cells, for e2am)le, hae (een found t6 hae mem(rane and cyto)lasmic

rece)tors, dis)laying the s)ecificity t6 the IAA (inding, and not sho'ing such

s)ecificity t6 a synthetic au2in ",$+& -",$+dichloro)heno2yacetic acid3 callus

gro'n in IAA+ and kinetin+containing medium formed a considera(le num(er of

roots, 'hile callus cells cultiated 'ith ",$+& did not form any roots 71$, ", "=8* In the )ea, the au2in+induced N+acyl+as)artate synthetase has (een sho'n

t6 (e synthesi:ed, not only in gro'ing tissues, (ut also in non+elongating and

non+res)onding t6 au2in action tissues -mature :ones, 'hose gro'th is limited

(y a deelo)ed cell 'all 7"#8* Similarly, it has (een found 7/!8 that au2in induces

the synthesis of identical kinds of m@NA (oth in elongating -a)ical and non+

elongating -(asal )arts of the soy hy)ocotyl, and, thus, it has (een )roed that

some au2in+regulated changes in gene e2)ression are common for organs

characteri:ed (y different gro'th res)onses*

%here are endogenous modulators of the au2in+(inding sites, 'hich )lay an

im)ortant )art in the gro'th control* Among them are, in )articular,

(en:o2asolinons found in corn and fungal to2in fusicoccin detected in the PM of

monocotyledonous and dicotelydonous )lants* It has (een sho'n that a multi)le

increase in the num(er of microsomal fusicoccine+(inding sites is o(sered

during the corn coleo)tile treatment 'ith IAA at a concentration of 1+1! DM for

1! + #! min 7/1+//8*

%he o(tained data indicate there is tem)orary control of the )lant rece)tor

synthesis* Eor e2am)le, a tem)orary rise of IAA+(inding rece)tor synthesis 'as

o(sered in 'heat roots during incu(ation in !*;= DM IAA for 1 h and in

mem(rane )re)arations of artichoke tu(er sections during a "$ h incu(ation)eriod in solutions 'ith ",$+& -1 DM 7/08*

7econdary messen9ers o? phytohormones. ?*F*Southerland 'as a'arded the

No(el Pri:e in 1#1 )roing that hormones cataly:e arious en:yme )rocesses in

cell+targets (y means of secondary messengers* It is no' 'idely acce)ted that

)lant and animal hormone secondary messengers are cGH -cyclic adenosyne

mono)hos)hate and cH -cyclic guanosyne mono)hos)hate4 'hen a hormone

affects a rece)tor the en:yme of adenylatcyclase, located on the mem(rane and

inoled in the cGH synthesis from A%P, is actiated* %hen cGH enters the

cyto)lasm and actiates arious )rotein kinases 'hich, in turn, may actiates)ecific cell en:ymes through )hos)horylation 7;8*

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Inositoltri)hos)hate is secondary messenger used in signal transduction in

)lant cells 7;, /;8* In this case a hormone effect on a rece)tor causes the

actiation of )hos)holi)ase C, 'hich hydroly:es )hos)hoinositol+$,0+

(i)hos)hate* As a result of this mem(rane com)onent hydrolysis, the t'o

secondary messengers -inositoltri)hos)hate and diacylglycerol are deliered into

the cyto)lasm* &iacylglycerol actiates )roteinkinase C, )laying a leading )art incontrolling a 'ide sco)e of )rocesses through a selectie en:yme

)hos)horylation*

A uniersal regulator for many hormonal signals is cyto)lasmatic calcium

7/8* Inositoltri)hos)hate stimulates calcium channels o)ening in the mem(rane

and, accordingly, coordinates a simultaneous release of secondary messengers

from the mem(rane reuired for the )rotein kinase actiation 7/;8* An increase of

the calcium leel in the cyto)lasm of )lant cells may (e a result of enironmental

effects3 stress, light, cold, )hysical or electrical stimulation as 'ell as hormones

7/=8* Calcium has a considera(le effect on the structural organi:ation, fore2am)le, of tu(uline in microtu(ules, on the mem(rane )ermea(ility ariation,

the actiity of the )rotein kinase en:yme, and in controling cytokinesis* Many cell

)hysiological res)onses t6 light -for e2am)le, )hytochrome functioning in )lants

are effected (y Ca" leels 7/#,$!8* %he most significant )art calcium )lays is in

hormone+controlled )rocesses3 e2ogenous Ca"may enhance effects of each of

fie )hytohormones 7$184 some data indicate that Ca" is a secondary au2in

messenger 7$"8*

Ca"has (een sho'n to e2ecute functions of secondary messenger during

signal transmission as a res)onse t6 the osmotic and other stresses 7$/8* S)ecific

rece)tors of Ca"ions, transmitting Ca"uniersal signals as s)ecific information

inside the cells, are arious Ca"+(inding )roteins -haing arious ?E+hand

domains that ensure Ca"(inding )rocess undergoing significant conformational

changes during Ca" addition* In higher )lants the )roteins of arious families,

such as calmoduline and )roteins related t6 it, act as Ca "Jsensors in res)onse t6

osmotic stress, linking calcium and calcium+de)endent en:ymes3

adenylatcyclases, )hos)holi)ases, NA& kinases, )hos)hodiesterases and,

therefore, are called Jregulatory or Jsensory )roteins of signals Ca"7$$, $08*

In Arabidopsis, for e2am)le, AtCP1 gene 'as identified, encoding a

)rotein similar t6 Ca"Jsensor calmodulin, 'hose e2)ression 'as induced (yNaCl 7$;8, and also t'o genes, encoding Ca"Jsensors similar t6 calciunerin B +

regulatory su(unit of the mammal )hos)hotase, 'ere isolated 7$8* It has (een

sho'n that the e2)ression of one of them L AtCBL1 gene is significantly

enhanced as a res)onse t6 arious stresses including drought, damages, and lo'

tem)eratures* Moreoer, in Arabidopsis there 'ere isolated genes encoding a

grou) of )rotein+kinases interacting 'ith )rotein, encoded (y AtCBL1gene, in a

Ca"+de)endent manner 7$=8* %he gene called SOS3-Salt 9erly Sensitie / has

(een reealed t6 encode the calciunerin su(unit in Arabidopsis 7$#8* Proteins,

encoded (y the SOS3gene, aid in )lant tolerance t6 high salt concentrations4ho'eer, their e2)ression does not change under stressful conditions* It has (een

suggested that calmodulins and calciunerins may control functions inoling

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)+glyco)rotein 1 gene hae sho'n that the hy)ere2)ression of AtP$P1 gene

results in some elongation of hy)ocotyls in seedlings gro'n in dim light4 at the

same time, )henoty)ically, anti+sense co+su))ression ofAtP$P1manifests itself

in some reduction of the hy)ocotyl length in seedlings gro'n in similar

conditions 7;=, ;#8* 9n the (asis of the a(oe o(serations it 'as suggested that

AtPP1 )rotein trans)orted IAA regulatory molecules (asi)etally from the IAA(iosynthesis :one -the seedling to), 'here AtP$P1e2)ression 'as ma2imum*

M&@ )roteins hae also (een inoled in the trans)ort of other )hytohormones

-for e2am)le, gi((erellins and (rassinosteroids 7;=8*

In Arabidopsis AtP$P1 and At!"#1 genes )lay an im)ortant )art in

gro'th control at (oth the 5uenile and mature deelo)ment stages, )artici)ating

in the au2in transfer and distri(ution4 according t6 the @NA (lot+analysis, the

At!"#1e2)ression is o(sered in seedlings, roots, rosette leaes, flo'ers and

a(oeground tissues (efore (olting -rosette leaes )lus shoot a)ical meristem

708* @NA (lot+analysis of trans+gene )lants -)ossessing $ k( u)stream seuenceof theAt!"#1gene, fused 'ith a re)orter gene of%+glucuronidase -$&S, and

'as )laced under an au2in+induced )romoter indicates that the e2ogenous IAA

induces the At!"#1e2)ression, 'hich reached its highest leel in the a)ical

meristem and young leaes of seedlings 70, !, 18* %hese results )roe that the

At!"#1 gene e2)ression is strictly controlled (y au2in*

enetic analysis of mutant atmdr1 and atmdr1atpgp1 seedlings

corro(orates the fact that the AtM&@1 and AtPP1 )roteins regulate the

homeostasis of au2in and are inoled in its distri(ution in all )lant tissues and

organs* It has (een esta(lished, for e2am)le, that At!"#1gene mutations result

in distur(ances of the au2in efflu2 in the )lace of its (iosynthesis L cotyledon

a)ical meristem, )etioles and young leaes of seedlings and in the increase of the

au2in concentration in these tissues a(oe the norm 70, ;#8* Au2in accumulation

in these organs is a result of their e)inastic )henoty)e and in mature )lants4 a high

au2in concentration (rings a(out a reduction of fertility* %he fertility defect

a))ears unrelated to gameto)hyte formation or function* Instead, it can (e

e2)lained (y inefficient deliery of )ollen t6 the stigma of the )istil caused of a

hy)erelongation of stamens 7" + 08* At the same time, At!"#1 andAtP$P1

gene mutations cause distur(ances in the au2in (asi)etal trans)ortation into other

organs and tissues and reducing a)ical domination -a )henomenon in 'hich au2intrans)orted (asi)etally inhi(its the gro'th of (asal lateral (uds* Such )henoty)es

are ty)ical for mutant au2in+resistant a'r1alleles of )lants 7;8*

In e2)eriments, inoling the a))lication of 7/.8+la(elled inhi(itor of au2in

trans)ort L 1+na)hthyl)hthalamic acid -/.+NPA a high degree of s)ecificity in/.+NPA (inding to a fraction of )urified AtNPA1 and AtPP1 )roteins 'as

reealed 7, =8* 9n the (asis of the o(tained data it 'as concluded that in

ArabidopsisAtNPA1andAtP$P1 genes encode au2in+and NPA+(inding )roteins

that regulate au2in distri(ution during )lant gro'th and deelo)ment*

It has (een esta(lished that in )lants the au2in trans)ort modulators arecalled flaonoids* It has, in )articular, (een sho'n that in )um)kin hy)ocotyls the

actiity of M&@ )roteins, inoled in the trans)ortation of IAA and NPA through


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cell PM, is strictly inhi(ited (y uercetin and kaem)ferol 70,#8* Erom the

results of studies on Arabidopsis )lants mutant in the (iosynthesis of

)henyl)ro)anoids also testify t6 a regulating effect of endogenous flaonoids on

the au2in tissue+s)ecific distri(ution 7 + =18*

&etailed genetic and (iochemical inestigations hae sho'n that in

addition t6 M&@+like trans)orters, )artici)ating in an actie A%P+moingtrans)ort of au2in, there are other )roteins im)lementing an energetically )assie

trans)ort of IAA 708* &uring the course of e2)eriments it 'as esta(lished that a

)roton form of au2in dominating in the cell 'all system -a)o)last 'as

electrically neutral and, therefore, its transference reuires an actie trans)ort

inoling M&@ )roteins4 at the same time, the energy )otential of the anion form

of IAA -dominating at a neutral ). of cyto)lasm is much higher inside the cell

than outside* %herefore, the )olar trans)ort of the anion form of au2in from the

(iosynthesis site t6 the a))ro)riate organs and tissues may (e affected )assiely

through PIN channels located in s)eciali:ed cells of the stem 7#, =", =/8*In recent years it has (een esta(lished that the family of P(N genes,

encoding )roteins inoled in the )olar au2in trans)ort 7=$ + =;8, includes a gene

haing seeral names -)(#1,P(N1,A$#1*AtP(N+, ,A-. since it 'as identified

inde)endently of arious mutants characteri:ed (y a distur(ed graitro)ism of

roots3 agr1 -agraitro)ic, /a. -'ay ; and ethylene+insensitie mutants eir1

-ethylene insensitie root 1 7=, ==8*)(#1 gene is a mem(er of the multigene

family in Arabidopsis3 in this )lant genome identified genes hae (een

characteri:ed (y a considera(le degree of homology regarding )(#1, arious

homological e2)ressing tags seuences -?S%s, and t'o similar o)en reading

frames -9@E 7=#8* %he related seuences of the A)01 and A)0+ genes

-homological seuences of the)(#1gene 'ere found in the clones %"(51" and

MK$ of the 1st and 0thchromosomes, res)ectiely* %he seuences similar t6

?S% of the genes3A)01,A)0+and#)01genes* Com)lementory root+s)ecific

k&NA 'ere also identified in rice that testified that)(#1 and its homologies are

classified as a family of genes uniersal for all higher )lants 7=;8*

Studies on eir13mutants hae sho'ed a considera(le restriction of the

e2)ression of the)(#1gene in roots4 at the same time, the agraitro)ic gro'th is

o(sered not only in roots (ut also in other )lant organs* It has (een ascertained

that the)(#1gene encodes the )rotein 'ith a molecular mass of ;# k&a, 'hichcontains 1! trans+mem(rane -%M domains4 )rotein encoded (y )(#1 gene

)ossesses amino acid seuences 'hich are on /0 + $!O identical 'ith those

)resent in (acterial mem(rane )roteins inoled in the trans)ort of arious

molecules through PM 7=0, =;8*

%his fact testifies that the )(#1 gene im)lements a trans)ort function*

Studies on the eir1 mutant )henoty)e hae esta(lised that the )(#1 gene is

inoled in the au2in trans)ort* ith the o(sered sta(ility to ethylene, eir1

)lants hae not e2hi(ited any sensitiity t6 inhi(itor of au2in trans)ort L ",/,0+

triiodo(en:oic acid -%IBA*%he inolement of ?I@1 in the root+s)ecific au2in distri(ution 'as

inestigated (y analysis of au2in+regulated At(AA1 gene e2)ression using the

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structure of the re)orter P($2$&S gene e2)ressing %+glucuronidase under

control of the )romoter geneAt(AA+ 7=;, =#8* As affected (y endogenous au2in

and graistimulation, the At(AA+ gene e2)ression 'as induced for seeral

minutes and occurred strictly in the root meristem of 'ild gro'ing )lants* In 'ild

)lant )rimary roots an asymmetric $&S+colouring in the elongation and

differentiation :ones 'as o(sered, 'hile the e2)ression of the P($2$&Sgenein eir13mutants 'as not influenced (y graistimulation, and it remained limited

in root ti)s* An introduction of e2ogenous au2in NAA -na)hthaleneacetic acid

into the medium caused an induction of the re)orter gene e2)ression in the

meristem and in the :one of root to) elongation (oth in 'ild )lants and in eir13

mutants, 'hich )resered their a(ility t6 res)ond t6 e2ogenous au2in action* It

'as found that eir1mutant roots 'ere less sensitie t6 ethylene and e2hi(ited

some resistance t6 synthetic inhi(itors of the au2in trans)ort 7=0, =;8* Eor

e2am)le, 'hen %IBA 'as used t6 treat eir1mutants they e2hi(ited sta(le leels

of the At(AA+ gene e2)ression, 'hile 'ild )lants dis)layed a reduced At(AA+gene e2)ression*

A reduced sensitiity of eir1mutants t6 ethylene as 'ell as t6 the au2in

trans)ort inhi(itors %IBA and NPA )roides eidence of the e2istence of

common signal com)onents for au2in and ethylene 7=;8* %hese mutant

)henoty)es are similar t6 that of .99K>?SS1 -hls1 mutants of Arabidopsis

7#!8* Since the 0LS1 gene controls the hy)ocotile a)ical :one, hls1 mutants

)ossess no a(ility to (end a to) of hy)ocotile during germination* %he 0LS1gene

e2)ression is induced 'hen )lants are treated 'ith ethylene causing cell

elongation and, at the same time, e2)ression of0LS1gene is re)ressed under the

effect of the au2in trans)ort inhi(itor NPA* ild )lant seedlings gro'n under the

effect of the NPA had the same )henoty)e as hls1mutants* %herefore, au2in

trans)ort inhi(itors cause a )lant res)onse similar t6 a defect res)onse of hls1

mutant a)e2es t6 ethylene influence* In roots of eir1 mutants, similar to those in

the hls1 mutant, a)e2es no graitro)ic effect under the influence of (oth

endogenous and e2ogenous ethylene as 'ell as negatie agraitro)ic effect under

the influence of au2in trans)ort inhi(itors are o(sered* %his cross+insensitiity t6

ethylene and au2in trans)ort inhi(itors is eoked (y mutations defectie in au2in

and ethylene res)onses and e2)lains the interaction (et'een au2in and ethylene

effects* %he a(oe o(serations conclude that ethylene+res)onsie genes maycontrol a cell differentiated gro'th, regulating the au2in distri(ution and its

actiity 7#!, #18*

%he information a(out the )(#1gene inolement in the au2in trans)ort

'as also o(tained in e2)eriments 'ith altered lateral roots -al41 andpin1mutants

Arabidopsis 'here high endogenous au2in leels contri(uted t6 the reduction of

lateral roots elongation 7#"8* In dou(le eir1al41 mutants, eir1 mutations

com)letely restored root elongation and agraitro)ism 'hich 'ere distur(ed as a

result of al41mutations* In studying functions of theP(N gene inpin1mutants the

a(sence of the initiation of flo'er (udding 'as o(sered4 it a))ears that thisdefect is associated 'ith a reduction of the au2in )olar trans)ort that is )roof that

the P(N gene is reuired for the au2in )olar trans)ort 7=08* %he P(N+ gene

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encoding a )rotein, 'hich is ;$O identical 'ith the )rotein encoded (y the P(N1

gene, 'as also identified and cloned 7==8* %he mutant pin+ lines Arabidopsis

mutageni:ed (y the ?n+1 trans)oson of corn sho'ed some defects in root

graitro)ism similar t6 those in eir1mutants* %he a))lication of the method of

res)onse com)lementation (et'een pin+ and /a.5+ mutations -'ith alleles

eir1 and agr1 demonstrated that these mutants are allelic, 'hile the seuenceanalysis confirmed thatP(N+is a gene similar t6)(#1, ,A-., andA$#1genes*

An im)ortant role in mediating the au2in )olar trans)ort through the cell

PM in s)ecific tissues of Arabidopsis is )layed (y the A&61gene encoding a

)rotein identical in its com)osition of $=0 amino acids 'ith )ermeases of

(acteria, fungi, and other )lants 7#/, #$8* %he )resence of 1!+suggested

mem(rane+(inding sites demonstrates AUQ1 )rotein mem(rane locali:ation*

&ata o(tained testify that this )rotein forms com)le2 'ith IAA )rotons and

trans)orts IAA through mem(ranes 'ith )artici)ation of the )roton )um) A%Pase

7#$8* %he AUQ1 )rotein )resence 'as detected in the )roto)hloem, central, and

lateral )arts of the root ca) as 'ell as in elongating e)idermal :ones of roots 7#/,

#$8* Phenoty)ically, A&61 gene mutations in )lants are similar t6 AtP(N3 and

A$#1*AtP(N+gene mutations -'ith distur(ances in the root graitro)ism 7#08

and manifested themseles in a selectie )lant insensitiity t6 au2ins IAA and

",$+& and, at the same time, sensitie t6 NAA -the last )henomenon can

)resuma(ly (e e2)lained (y the fact that the AUQ1 )rotein is not inoled in

NAA transition through mem(ranes 7=;, #$8* A com)aratie analysis of AUQ1,

A@1RAtPIN", and AtPIN/ )rotein functions has sho'n that AtPIN/ regulates

the trans)ortation of au2in through cell mem(ranes in a)ical :ones of the root

ca), 'hile AUQ1 and A@1RAtPIN" are res)onsi(le for the (asi)etal trans)ort

of au2in from the root ca) t6 elongating :ones of )lant organs 7#$ + #;8*

enetic and molecular+(iological analyses 'ere used t6 isolate and clone

the geneA#$1-A>%?@?& @?SP9NS? T @AFI% regulating the actiity

of PIN and AUQ1 )roteins inoled in the au2in )olar trans)ort 7#/8* Studies on

a functional role of A#$1 in mechanisms of the )lant root and hy)ocotyl

graitro)ism hae sho'n that A#$1 encodes a )rotein confined to (asal

)eri)heral mem(ranes of s)eciali:ed graity+sensitie e)idermal and cortical

cells -statocytes containing statolithes + amylo)lasts in the elongating :ones ofroots -central )art of the root ca) and shoots -coleo)tiles, hy)ocotyls, and

internodes 7#8* It has (een ascertained that the amylo)last shift and

sedimentation actiate an asymmetric redistri(ution of au2in through gro'ing

organ mem(ranes and that is accom)anied 'ith the accumulation of au2in high

concentrations in the a)ical :ones of roots resulting in some retardation of root

cell elongation and, at the same time, t6 some enhancement in the shoot cell

elongation 7#=8* %hese )rocesses cause a graitro)ic differentiated gro'th of

organs3 roots + do'n'ards and shoots L u)'ards* It has (een esta(lished that the

amylo)last sedimentation occurred inside the net of actinic filaments denselyinterlaced 'ith the cortical ?@ and attached their ends t6 the )lasmatic mem(rane

7##8* It is suggested that cytoskeleton and ?@ restructuring that occurred under

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mechanical influences actiated the transition of graitro)ic signals (y means of

the mem(rane channels actiity regulation 71!!8* In com)liance 'ith this

suggestion, transition ariations in the Ca" ions flo' and shift the cyto)lasm ).

t6 the alkali side and are classified as cell res)onses t6 graitational stimulation

7## + 1!/8*

It 'as ascertained that the main )art in these res)onses of )lant cells t6graitro)ic signals 'as )layed (y the &naV+like )rotein, encoded (y the A#$1

gene, associated 'ith PM, INC?P% )roteins of the cytoskeleton -cytoskeleton+

interacting )roteins, 'ith mem(ranes of ?@ and trans+olgi net'ork -%N and

)ossessing a conseratie V domain, located at the N+end and contiguous t6 the

hydro)ho(ic and C+terminal s)iral+sha)ed regions 7#/, 1!18* &na(V+)roteins are

also 'idely s)read in )scherichia coli, fungi, and humans4 the conseratie

tri)e)tide .P& aaila(le inside the V domain of these )roteins 'as found t6 (e

reuired for the )romotion of A%Pase actiity in the molecule of )rotein

cha)erone .s)! -and its homologues, 'hich interacts 'ith &na(V+like )roteins71!$8* Among many intra+cellular functions im)lemented (y &na(V+like )roteins,

together 'ith .s)!s and other heat+shock )roteins in arious organisms, the

most im)ortant are3 induction of )rotein coagulation as a res)onse t6 heat stress

in)scherichia coli71!$84 inolement of yeast &na(V+like d51)RMas0) )roteins

in the trans)ort of arious )roteins in ?@ and mitochondria 71!084 interaction of

&na(V+like )roteins + au2illins -found in fungi and mammals 'ith cha)erone

.sc! follo'ed (y a disassem(led clathrin triskelia from clathrin+coated esicles

during endocytosis 71!;84 cha)erone .sc! stimulation of the release from

endocytosis esicles of the mem(rane+associated trans)ort )rotein kinesin

-containing the V domain in regions of tandem re)eats regulating the a2onal

organelle motion in suid 71!8*

Although &na(V+like )roteins are )resent in all ta2onomic grou)s of

lo'er and higher organisms, homologues of the A@1 )rotein hae (een detected

only in nematodes and )lants 7#/, 1!18* It has (een esta(lished that in )lants these

)roteins im)lement s)ecial regulatory functions consisting in3 control of the )olar

distri(ution of s)ecific mem(rane )roteins in a diiding cell )late during

cytokinesis, regulation of the motion of endocytosis esicles -synthesi:ed in ?@

or %N containing au2in trans)orters -for e2am)le, AtPIN1 and A@RAtPIN"

)roteins in Arabidopsis or .+A%Pases of )lasmatic mem(ranes (et'een theintracellular com)artments and PM as 'ell as transmission of early graitro)ic

signals inside statocytes 7 #/, 1!= + 11!8*

%he role of the A@1 )rotein in the regulation of graitro)ism in

Arabidopsishas (een studied in detail3 it has (een found that this )rotein affects

the Jalkali:ation of cyto)lasm -increasing its ). from *" t6 *0 and, at the

same time, causes some reduction in the a)o)last ). that (ring a(out conditions

reuired for normal root graitro)ism -that is setting different gradient of . ions

necessary for the )olar trans)ort of the anion form of IAA 71!", 1!/, 1118* No

increase has (een detected in the cyto)lasm ). of statocytes of roots andhy)ocotyls of agr1+mutant )lants as a res)onse t6 graistimulation -Eig* 14

conseuently, cells of the root ca) of ertically gro'ing roots of agr1+mutant

11


12/50

)lants accumulate higher -than in normal )lants leels of au2ins and the au2in

)olar trans)ort through mem(ranes of mutant cells is distur(ed and that is one of

the reasons 'hy the (asi)etal au2in efflu2 from the root ca) cells t6 the

elongation :one sto)s 7#/8* %he data o(tained gie )roof to the hy)othesis that

A@1 is inoled in the transmission of graitro)ic signals in statocytes 'here it

(rings a(out changes in ). and distri(ution of au2in*%he results indicating that the au2in )olar trans)ort may (e regulated

through )rotein )hos)horylation 'ere o(tained 711"8* It has (een ascertained that

this )rocess is controlled (y the heterotrimer )rotein )hos)hotase "A -PP"A,

'hich is a regulatory com)le2 consisting of catalytic C and regulatory A and B

su(units modulating the en:yme actiity of PP"A and mediating its interaction

'ith other )roteins 711/, 11$8* Biochemical and )harmacological inestigations

indicate that the role of PP"A in mediating )lant res)onses t6 the influence of

)hytohormones, )athogens, and lo' tem)eratures is significant4 it 'as esta(lished

that PP"A )artici)ated in the regulation of many )hysiological )rocesses, in)articular, in the regulation of stoma cell ion channel actiity, in the control of

cell diision and elongation, and )lant mor)hogenesis as a 'hole 7110, 11;8*

By using of molecular+genetic techniues, it has (een esta(lished that the

num(er of heterotrimer isoforms PP"A in the genome of Arabidopsis is a(out

"004 genes encoding 0 catalytic C su(units and also /A and 1B regulatory

su(units hae (een identified 711/8* A high leel of the re)orter gene e2)ression

under the )romoters of four of these genes has (een o(sered in seedlings, leaes,

and floral organs of transformed )lants 711;8*

9nly " mutant lines of Arabidopsis L rcn1 -roots curl in

na)hthyl)hthalamic acid and ton+*4ass*gordo + hae (een isolated 7110 + 118* It

has (een ascertained that the gene #CN1 encodes A1 or W isoform of the

regulatory su(unit A, 'hile the gene 7ON+*8ASS*$O#"Oencodes the B su(unit*

In ton+*4ass*gordomutants the mor)hogenesis is distur(ed, the arrangement of

microtu(ules in cells is disorgani:ed, the ethylene synthesis increases, and au2in

concentration rises 711084 'hereas the rcn1 mutation (rings a(out differentiated

defectie )hysiological res)onses including distur(ances in the cell elongation,

au2in )olar trans)ort, graitro)ism of roots and shoots, increases in ethylene

(iosynthesis as 'ell as distur(ances in )hysiological res)onses t6 the action of

ABA* 9n one hand, increased au2in accumulation in the rcn1 )lants hy)ocotyl-as a result of the distur(ance of its trans)ort into roots enhances these )lants

rece)tiity for the au2in trans)ort inhi(itor L na)hthyl)hthalamic acid -NPA +

the a))lication of 'hich results in agraitro)ism -i*e*, hy)ercurling in these

)lant roots 711", 11;, 118* 9n the other hand, it has (een sho'n that an

e2ogenous treatment of 'ild )lants 'ith lo' doses of the inhi(itor PP"A causes

)henoty)ic features ty)ical of rcn1mutant )lants 711$, 11;8*

In the 'ork 711"8 the mutant gene rcn1'as introduced into transferred+

&NA and flanking seuences )roiding t+&NA (uilding into the genome 'ere

cloned* %he analysis of the k&NA #CN1gene in transformed )lants hae sho'nthat the insertion of t+&NA 'ith the gene rcn1 destroys the gene of the regulatory

su(unit A of the )rotein+)has)hotase "A -PP"A+A a su(stance+target 'hich may

1"


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(e PIN+trans)orters* %he #CN1 gene conerts mutant )henoty)es rcn1 of

Arabidopsis and tem)erature+sensitie trd31-resulting from mutation PP"A+A

of Sacharomyces cereisiae into a normal )henoty)e* %hese results sho' that

PP"A+A )erforms a regulatory function in au2in trans)ort*

%he e2)erimental data o(tained in recent years indicate that in addition t6

the a(oe t'o kinds of intra+ and inter+cellular trans)ort of au2in L actie A%P+controlled trans)ort of IAA -effected (y the M&@+)rotein family and

energetically )assie )olar trans)ort of IAA -inoling PIN )roteins, the )lants

and fungi also )ossess the esicular intra+cellular trans)ort of au2in* Studies on

the mechanisms of IAA esicular trans)ort hae led t6 the discoery of a

numerous family -7( genes of SNA@? )roteins+rece)tors -solu(le NSE -N+

ethylmaleimide+sensitie factor attachment )rotein rece)tors inoled in the

au2in trans)ort t6 organelles, formed (y the endomem(rane system -?@, %N,

PFC, acuole and endosomes 711=8*

In com)liance 'ith their differentiated locali:ation and functions, SNA@?sare diided into t'o grou)s L esicular SNA@?s -+SNA@?s 711#8 and

locali:ed in mem(rane+targets t+SNA@?s -haing s)iral+sha)ed domains reuired

for the interaction 'ith +SNA@? )roteins 71"!8* It has (een found that each

three mem(rane t+SNA@? rece)tors form the cis+SNA@? com)le2 that is

)erceied (y one esicular +SNA@? rece)tor ena(ling their s)iral+sha)ed

domains t6 form four s)iral (unches* %his com)le2 formation contri(utes t6 the

fusion of esicular mem(ranes and mem(rane+targets, resulting in a SNA@?+

trans)orted au2in )enetration into com)artment+targets follo'ed (y the formed

com)le2 dissociation -it has (een found that this energy+consuming )rocess

reuires the )resence of solu(le NSE and W+SNAP )roteins and the return of

restored +SNA@?s into the initial com)artments*

More than 00 SNA@?s, encoded (y the multigene family that em)hasi:es

the e2istence of the )lant com)le2 endo+mem(rane system, hae (een identified

inArabidopsis using genetic and molecular+(iological techniues 711=, 1"1+1"/8*

At )resent, the most studied and characteri:ed family is that of -7( genes

consisting of three closely related mem(ers3 -7(11, -7(1+, and -7(134 a high

leel of their e2)ression is o(sered in all organs 711=8* It has (een ascertained

that the )roteins encoded (y -7(11 and -7(1+ genes hae ;!O amino acid

seuence similarity and e2hi(it "0 O seuence identity to yeast Fti1) )roteinssimilar t6Fti1a )roteins )resent in mammals 71"18*

enetic engineering techniues hae esta(lished that F%I11 and F%I1"

)roteins trans)ort esicles containing arious )roteins along arious )ath'ays*

Eor e2am)le, it has (een sho'n that during the transformation of ti1

tem)erature+sensitie and :ero mutant ti1 alleles of yeast -com)lementary t6

-7(11 and -7(+ alleles of )lants (y the -7(11 gene they e2hi(it some

su))ression of )henoty)ical gro'th defects resulting from the distur(ance in the

)rotein trans)ort along the CP )ath'ay -through PFC* At the same time, the

transformation of these mutants (y the -7(1+gene (rings a(out a resum)tion ofthe API )roteins trans)ort from cyto)lasm t6 acuole -along the Cyt )ath'ay

and along the A>P )ath'ay -through the olgi a))aratus 711=, 1"$8* According

1/


14/50

t6 the results of studies, the F%I11 )rotein functions as +SNA@?s3 confined t6

%N mem(ranes this )rotein makes com)le2es 'ith the ?>P rece)tor )rotein

s)ecifically (inding )roteins trans)orted from acuoles4 in case of its locali:ation

in PFC mem(ranes the F%I11 )rotein forms com)le2es 'ith grou)s of SP" and

SP0 )roteins Lsynta2ins sho'ing a s)ecificity in the interaction 'ith N%PP

)roteins trans)orted (y esicles from %N t6 PFC 71"/ + 1";8*A genetic analysis of Arabidopsis'ith mutant -7(11and -7(1+ genes has

confirmed their differentiated regulatory role* It has (een sho'n that ti1+

mutants gro'n on medium rich in nutrients dis)lay a normal )henoty)e, 'hile

)lants gro'n on medium )oor in nutrients dis)lay an accelerated aging that

em)hasi:es the im)ortant role of -7(1+ in )lant auto)hagy 711=, 1"8* -7(11

gene mutations 'ere identified in zig mutants characteri:ed (y a )ronounced

distur(ance in shoot graitro)ism -similar )henoty)e is ty)ical of pin3 mutants

71"84 ti11zigmutant 'ere sho'n t6 hae defects in the ascular structure and

distur(ed au2in trans)ort 71"=8* .ystologic studies hae sho'n that zig mutantendodermal cells do not dis)lay the sedimentation of amylo)lasts acting as

statolithes in 'ild and ti1+ mutant )lants 711=8*

It has (een ascertained that -7(11 encodes XIRS@$+SNA@? )rotein

'hose mutations cause defects in the shoot graitro)ism 71"#8* Besides, )roteins

encoded -7(11 and -7(1+ genes hae (een found to (e a(le t6 re)lace one

another during the formation of SNA@?s com)le2es* Studies of crosszig ti1+

mutations as 'ell as ti11 ti1+mutations 'ere sho'n that these mutations are

similar t6 lethal for em(ryo cl1-acuoles 1 mutations in 'hich the em(ryo

deelo)ment terminates at the tor)edo stage 71/!8*Arabidopsis -CL1gene has

(een determined t6 encode the )rotein homologue F)s1;) of the yeast )rotein L a

com)onent of the FPS com)le2 of class C controlling the trans)ort of )roteins

from the olgi a))aratus into acuoles* In yeast the FPS com)le2 of class C

mediates the intrusion of trans+SNA@? )roteins in the Ftil)+Fam+Fam/

com)le2 71/184 inArabidopsis the mem(ers of the FC>1 com)le2 are )rotein+

synta2ins of the SP" ty)e, 'hich interact 'ith F%I11 )roteins 71"", 1"/, 1"0,

1/"8* It is suggested that 'ith dou(le ti11 ti1+ mutations the au2in and )rotein

esicular trans)ort is distur(ed as a result of the distur(ance in the FC>1

com)le2 formation and that is the reason 'hy the em(ryo dies at this same stage

of deelo)ment as it is o(sered in cl1 mutants 711=8* %he results of thesestudies )roe undou(tedly of the key role of the -7(11 gene encoding the

XIRS@$+SNA@? )rotein during the intracellular esicular trans)ort of au2in*

By no', the data )roing the e2istence of )rotein+trans)orters of au2in

con5ugates (eing IAA reseres hae (een o(tained* Eor e2am)le, it has (een

esta(lished that the )rotein+trans)orter AtM@P0 71//8 'as inoled in the

trans)ort of con5ugated IAA forms although the free IAA -formed 'ith the

)artici)ation of I>@1, IA@1, IA@/ hydrolases 71/$, 1/08 has (een sho'n t6 (e

trans)orted from hy)ocotyl cells t6 other tissues ofArabidopsismore freuently

than its con5ugates 70, ;"8*u=inre9ulated 9enes. A great num(er of au2in+controlled families ofAu'*(AA,

SA-Small Au2in U) @NA and $03genes has (een isolated from elongating

1$


15/50

:ones of ethyolated hy)ocotyls or e)icotyls at such )lants as a )ea -for e2am)le,

PS(AA2*5, PS*(AA. and SA genes, soy -for e2am)le, $mAu'++9 $mAu'+:

and $031genes, corn -for e2am)le,ZmSA+gene, (ean, to(acco, tomato,

and Arabidopsis-more than "!Au'*(AAgenes and !AtSA homoloues 71/;

+1$/8* %heAu'*(AAgene family has also (een found in monocotyledonous and

gymnos)erms )lants 71/#8* Besides, there are also aaila(le data concerning aregulating au2in effect on the e2)ression of the family ofA$Sgenes encoding the

synthase of 1+aminocyclo)ro)an+1+car(onic acid L a key en:yme of the ethylene

synthesis, the family of NAC1genes and glutation+S+transferase 7"", "0, 1/;,

1$$8*

It has (een esta(lished that au2in induces the e2)ression of Au'*(AA,

SA C03, andACSgenes for seeral minutes s)ecifically in the a(sence of the

)rotein (iosynthesis de nooon the (asis of 'hich these genes are classified as

au2in )rimary+regulated genes 71/# + 1$/8* %he au2in induction of Au'*(AA9

SA C03, and ACSgenes e2)ression is also o(sered in the )resence of an)rotein synthesis inhi(itor cyclohe2imide -C.Q that )roides eidence of the

au2in a(ility t6 de+re)ress the transcri)tion or t6 control the m@NA synthesis

71/; + 1/#, 1$$8*

%he Au'*(AA gene family is most thoroughly descri(ed for Arabidopsis*

Some genes, for e2am)le, CS(AA19 CS(AA+, and CS(AA3hae (een cloned4

the k&NA am)lified regions of these genes hae (een found t6 encode )rotein

amino acid seuences identical 'ith those )resent in )roteins encoded (y the

(AA++ gene -$O of soy, (y (AA; genes -01O and (y (AA2 genes -0#O in

Arabidopsis 71/8* Au2in+regulated genes hae (een esta(lished as haing a

tissue+s)ecific tendency of e2)ression that indicates that different tissues are

characteri:ed (y the diersity in au2in res)onses*

%he use of genetic analysis techniues has sho'n that semidominant

mutations of au2in+controlled S0


16/50

-containing a re)orter $&S gene of %+glucuronidase )scherichia coli under a

)romoter of the au2in+regulated S0


17/50

gated ion channel )rotein, and many other )resently identified genes for the

detailed list refered t6 in the reie' 71$/8*

%he genetic analysis data hae indicated that the re)ression of the )rimary

au2in+induced genes inoles(AA+:andA6#+*(AA=genes 'hich, along 'ith the

S0


18/50

com)arison 'ith 'ild )lants transformed (y the BA$&S ector* %he tissue+

s)ecific increase in sensitiity t6 the au2in 'as accom)anied (y a high leel of

the $&S gene actiity in other )arts of mutant seedlings, too*

Studies on the $&S gene actiity in the root elongating :one of age+

mutants transformed (y BA$&Shae esta(lished that the e2)ression leel of

this gene is similar t6 that of the 'ild )lant treated 'ith 1!+=

or 1!+

M IAA, 'hilean increase in the $&Sgene actiity in ascular tissues of roots and hy)ocotyl

does not de)end on the au2in effect* Com)aratie studies on the influence of

age1 and age+mutations on the e2)ression of earlyR)rimary au2in+res)onsie

genes hae sho'n that in age 1seedlings the transcri)tion leel of early au2in+

res)onsie(AA19 (AA2, and(AA5 genes increases after the au2in effect (ut does

not reach that high leel o(sered in 'ild )lants, 'hile in com)arison 'ith 'ild

)lants, the age+mutants in the a(sence of the au2in accumulate higher leels of

the(AA1 and(AA1+ gene transcri)ts and the leels of(AA2gene transcri)ts are

similar t6 those of 'ild )lants* It has (een found that in age1and age +mutantsthe hy)ere2)ression of the t'o earlyR)rimary au2in+induced genes causes a

ty)ical mor)hology defectie for the au2in effect3 (oth s)ecies are shot and

(ushy, ho'eer, age1)lants also hae a distur(ed mor)hology of leaes and

roots and a different )eriod of flo'ering 710$ + 10;8*

A family of SAgenes, first isolated from soy elongating hy)ocotyl cells,

is also classified as )rimary au2in+regulated genes* In recent years SA genes

hae (een identified in many other )lants3 mung (ean, soy(ean, rYdish, )ea,

Arabidopsis, to(acco, a))le+tree, and most recently in corn 71/#, 1$", 10=8* In

com)liance 'ith the genome analysis results,Arabidopsishas (een found t6 hae

more than ! homologues of SA genes, and as it has no' (een esta(lished

that only 11 of them encode )roteins L au2in signal com)onents -it has (een

sho'n that the e2)ression of 1! SA genes is induced and only one SA.

gene is re)ressed (y au2in 71/#8* %he au2in induction effect on the SAgene

e2)ression is )roed (y the results of e2)eriments giing eidence that in shy+

mutant seedlings of Arabidopsis -)roducing a hy)ere2)ression effect on

S09 SA SA SA., and

SA+5genes is com)letely remoed -in com)arison 'ith 'ild )lants, 'hile its

re)ressie effect on the SA.gene e2)ression and lack of any changes ine2)ression of SA9 SA+9 SA+9 andSA. genes -that are not au2in+

regulated genes are similar t6 these of 'ild )lants 71$", 1$/8*

Similar results hae (een o(tained in the shy+mutant under transformation

(y the SAAC1$&Sgenetic structure -containing a re)orter $&Sgene under

an au2in+regulated )romoter of the SA gene -initially called SAAC1* It

has (een sho'n that the SAAC1$&Se2)ression is o(sered in elongating

:ones of hy)ocotyls gro'n in darkness and in hy)ocotyls, cotyledons, )rimary

leaes, and moderately in roots of 'ild )lants gro'n in light4 at the same time, in

shy+ mutants (oth in darkness and in light the SAAC1$&Se2)ression leelis much lo'er than that of 'ild )lants and reaches its lo'est leel in com)arison

'ith hy)ocotyls in cotyledons and meristems* %he data o(tained corro(orate that

1=


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the au2in dis)lays its tissue+s)ecific regulating effect on the SA gene

e2)ression in 'ild )lants and )roe that in shy+mutants the transmission of

au2in signals is distur(ed (y S."RIAA/ )roteins+re)ressors*

%here are some other data giing eidence of an au2in stimulating effect on

the SAgene e2)ression* It has, for e2am)le, (een sho'n that in au2in+treated

hori:ontally gro'ing soy seedlings the SA gene e2)ression (ecomesasymmetric as a result of 'hich the leel of m@NA SAon the lo'er side of

hy)ocotyl increases in com)arison 'ith that of the o))osite u))er side 71;8* %he

results of these studies )roe that the asymmetric e2)ression of SA genes is a

conseuence of a lateral au2in distri(ution in graitro)ically stimulated stems -in

com)liance 'ith the Kholodny+ent hy)othesis* It has also (een sho'n that the

au2in induces an emergence of SA m@NA transcri)ts for "+0 min -i*e*,

)roduces a regulating effect at the transcri)tion leel4 C.Q treatment neither

inhi(its nor enhances the au2in+induced transcri)tion actiity of SAgenes4 on

the contrary, the leel of SA transcri)t increase, as affected (y the au2in, issimilar t6 that of C.Q+untreated )lants 71/#, 10#8* %he seuence analysis of three

SA k&NA of soy has sho'n that they are deoid of intrones and contain o)en

reading frames -encoding )roteins 'ith a molecular mass of #+1! k&a 'ith a

high degree of homology of C+terminal seuences )resent 71;!8* %he SAgenes

e2)ression is tissue+s)ecific, dominant in the elongating :one of hy)ocotyls and

more moderate in e)idermal and cortical cells4 the au2in dis)lays its stimulating

effect on the SAgenes e2)ression in all these tissues 71/#8*

Eunctional features of SAgenes inArabidopsishae also (een studied

in detail 71$"8* All SA genes in Arabidopsis -e2ce)t AtSA hae (een

found t6 (e deoid of intrones4 m@NA encoded (y these genes are unsta(le 'ith

a uick turnoer -i*e*, (iosynthesis and decom)osition 'hich a))ears t6 (e

controlled at the leel of the conseratie &S% element of /Z+non+translated

region of m@NA and also (y elements inside 9@E+ encoding regions of m@NA

71;! + 1;/8* %he SAgene e2)ression has (een sho'n t6 (e controlled not only

at the transcri)tional, (ut also at the )ost+transcri)tional and )ost+translational

leels 71/=8* Unlike soy, C.Q induces the au2in+regulated synthesis of SA

m@NA inArabidopsis -for e2am)le, SAAC1transcri)tion*

%he homologue of SA genes 'as identified 'hen )hytohormone+

regulated )hysiological res)onses in corn coleo)tiles L the organs used as a modelsystem t6 inestigate cell gro'th and tro)isms, had (een studied* &uring the gene

k&NA li(rary screening, the k&NA clone, marked asZmSA+according t6 its

SAgene homology, 'as isolated and descri(ed from au2in+treated elongating

corn hy)ocotyls 71$"8* It 'as found that the ZmSA+ gene )ossesses the

characteristics ty)ical of )rimary au2in+regulated genes4 it has, in )articular, (een

sho'n that IAA and its synthetic analogues W+NAA, ",$+& as 'ell as the )rotein

(iosynthesis inhi(itor C.Q induce this gene e2)ression for seeral minutes -a

stimulating effect of C.Q on theZmSA+ gene e2)ression is e2)lained (y the

fact that in the regulation of theZmSA+ gene transcri)tion )artici)ates eitherthe endogenous )ool of re)ressors or (y the la(ility of the nuclease res)onsi(le

for the @NA degradation 71/;, 1$"8*

1#


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%he seuence analysis has reealed N>S -Nuclear >ocali:ation Signal and

&S% seuences -'hich are kno'n t6 )roide a uick degradation of SA

transcri)ts in all mem(ers of the SA gene family 71/#, 1;! + 1;/8*

?2)eriments on the transformation of e)idermal cells in the onion genetic

structure containing the re)orter $&Sgene, installed in /[ end of the encoding

region of the ZmSA+ gene under control of a strong constitutie CaMF-Cauliflo'er mosaic irus /0S )romoter as 'ell as the follo'ing histochemical

analysis of the )rotein encoded (y the chimerical ZmSA+$&S gene gie

su))ort to the e2clusiely nuclear locali:ation of this )rotein 71$"8*

6 determine the half+life )eriod of XmSAU@" )roteins in the cell+free

system of 'heat seedlings in itroin the )resence of 7/0S8+methionineRcysteine,

XmSAU@" )roteins 'ere synthesi:ed on the matri2 of )oly-A m@NA -isolated

from coleo)tiles* Simultaneously, XmSAU@" )roteins in coleo)tiles in io'ere

)ulse+la(elled 'ith 7/0S8+methionineRcysteine in the )resence of the au2in (y

re)lacing the radioactie amino acids 'ith non+radioactie ones* In short interalsof time the XmSAU@" )roteins 'ere )roduced from coleo)tiles and )urified* %he

)roteins synthesi:ed in itro -control and in io -e2)eriment 'ere immuno+

)reci)itated 'ith anti+(odies -'hich 'ere o(tained (y the immuni:ation of

ra((its 'ith recom(inant anti+gene + maltose+(inding )rotein33XmSAU@"

e2)ressed in )?coli and )urified (y affinity chromatogra)hy* By means of the

S&S+)olyacrylamid gel electro)horesis follo'ed the gel radio+autogra)hy, the

radio+actiity leel of )reci)itant XmSAU@" s)ots 'as measured* %he results

o(tained sho'ed that life of XmSAU@" )roteins 'as short and their half+decay

)eriod 'as min 71$"8*

&ata, reealing that the )rotein calmodulin -CaM is s)ecifically (ound in

itro'ith the )rotein encoded (yZmSAgene, e2)ressed in the heterological

system)?coli, or 'ith synthetic )e)tides haing amino acid seuences identical to

those )resent in )roteins encoded (y the cornZmSA>A5gene, (yAtSA

AC1 gene of Arabidopsis and (y soy SA>A5 gene hae (een o(tained*

According to results of these inestigations a suggestion is )ro)osed that

ZmSA+is a calmodulin+(inding )rotein -CaM+(inding )rotein and is )ro(a(ly

inoled in the au2in signal transmission through the Ca"RCaM secondary

messengers system 71$", 10=8*

Su(seuent e2)eriments hae erified this hy)othesis* Eor e2am)le, theseuence analysis of the XmSAU@" )rotein secondary structure reealed W+s)iral

sections in the N+terminal III and IF domains similar t6 am)hi)hilic W+helical

domains found in )lant Ca"RCaM+de)endent )roteinkinases -CCaMK, in the

&NA+(inding transcri)tional factors, interacting 'ith CaM as 'ell as in SAU@

)roteins4 the data concerning the formation of a sta(le com)le2 of 7/0S8+la(elled

XmSAU@" )roteins 'ith CaM (oine )roteins in the )resence of Ca " ions in

itro 'ere also o(tained 71/#, 1$", 10=, 1;$8*

%he family of $03 genes found in dicotyledonous and monocotyledonous

)lants as 'ell as in fungi, (lue+green algae, and "rosophilais also classified as afamily of earlyR)rimary genes 'hose e2)ression is controlled (y au2in 71/#8* It

has, for e2am)le, (een sho'n that in soy seedlings, lacking an e2ogenous au2in,

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the leel of m@NA $03is rather lo' and is mainly associated 'ith the ascular

system4 e2ogenous au2in treatment induces the $03 e2)ression in many )lant

tissues and organs* Unlike au2in+regulatedAu'*(AAand SA m@NA, the leel

of $03 m@NA remains unchanged under influencing of )rotein (iosynthesis

inhi(itor C.Q 71/#8* Presently, a )rotein has (een identified 'ith a molecular

mass of ! k&a, )ossessing a cyto)lasmatic locali:ation and is a mem(er of themulti+gene family of soy ./ )roteins ho'eer4 its functions hae not yet (een

determined 71;08*

%he num(er of Arabidopsismem(ers of the ./ gene family that hae

already (een identified is 1#, the most characteri:ed of 'hich are $0319 $03+9

$0339 $0359 $03.9 $03119 $03129 and $031= genes4 t6 see if their

e2)ression is induced (y au2in, the 9@E of these genes hae (een cloned 71/#8*

%he conducted studies reeal that a 1*0 h treatment (y the synthetic au2in NAA

stimulates the e2)ression of all of the a(oe genes -e2ce)t $031=*

?2)eriments on studying an inhi(iting effect of semidominantshy+ mutations onthe e2)ression of some of the $03 gene family mem(ers -$0319 $03+9 $03

39 $035 hae sho'n that the au2in induction of the $033and $035genes

e2)ression is reduced (y "!+0!O and the $031 gene e2)ression decreases

insignificantly as com)ared t6 that of 'ild )lants4 at the same time, the leel of

the $03+gene e2)ression is )ractically normal, similar t6 that of 'ild )lants

71$/8* %hese data indicate that the $031, $033, and $035 genes are

classified as au2in+regulated ones4 their e2)ression is induced (y the au2in in

'ild )lants and, at the same time, is re)ressed (y S0?SS1 gene thataccom)lishes a differentiated control of cell gro'th during the formation of

hy)ocotyl a)ical hook 7#84 genes of meta(olic en:ymes -e* g*, )roteins of the

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cytochrome family P$0!, similar t6 mytochonria )roteins A%Pase, IAA+%+

glycosyltransferase -controlling au2in+regulated reactions (y means of IAA

con5ugation4 genes of )roteins L transcri)tional trans+factors -au2in+res)onse

factor LA@E and )rotein similar t6 the translational factor ?E+1W4 >?A ->ate

?m(ryogenesis A(undant genes of )roteins + dehydrins -'hich )rotect cell

mem(ranes and other cell )roteins against high 'ater losses and many otherau2in+induced genes*

A2in+re)ressed genes are 71$/83 genes of some transcri)tional factors -for

e2am)le, Xinc finger )rotein, @IN+." finger )rotein @.A$a, @"@/+MB

transfactor, and @K &NA+(iding )rotein4 genes of rece)tor )roteins -e* g*,

those similar t6 histidinekinase and )roteinkinase4 genes of trans)ort )roteins

-e*g*, those similar t6 nodulin+";4 genes of meta(olic en:ymes -e*g*, )ero2idase,

endochitinase, )ectinesterase, )rotein from the family cytochrome P$0!4 gene of

the @NA+(inding )rotein4 geneNP03-non)hototro)ic hy)ocotyl+/ inoled in

the )hototro)ism control and other genes*%he a(oe information is surely )roof that the au2in controls the

e2)ression of the 'hole gene net'ork and, as a result, controls the )rotein

turnoer*

3olecular mechanisms o? the 9ene e=pression control by au=ins. Ithas no'

(een esta(lished that the key role in the au2in signal mediation is )layed (y

regulatory Au2RIAA, SAU@, and ./ )roteins as 'ell as (y the au2in res)onse

factors -A@E )roteins 71/; + 1/#, 1; + 1"8*

%he family of au2in+regulatedAu'*(AAgenes ofArabidopsis -com)rising

"# mem(ers has (een sho'n t6 encode )roteins, a molecular mass of "0+/0 k&a,

)ossessing the common conseratie I L IF domains and t'o conseratie signals

of the nuclear locali:ation -N>S3 N+terminal and C+terminal that s)eaks for their

nuclear locali:ation 71/#, 1! + 1"8* It has (een sho'n that the half+decay )eriod

of many nuclear Au2RIAA )roteins is 0 t6 1! min -e* g*, the half+decay )eriod of

nuclear PS+IAA $ and PS+IAA ; )roteins of )ea is similar t6 that of XmSAU@"

)roteins and amounts t6 ;+= min 7!, 1/=, 1$"84 an im)ortant role in the

Au2RIAA )roteins desta(ila:ing )rocess is )layed (y the II domain -containing a

seuence of 1/ amino acid residues called degron (eing a target for the )roteins

u(iuitination and their further degradation in the )roteasome 7"", 1/, 1$8* %he

immunological techniue inoling the use of 7/0S8+la(elled )roteins determinedthat the leel of Au2RIAA )roteins in )lants, mutant in the II domain of

IAA1RAQ@/ )roteins, increases and the time of their e2istence in com)arison

'ith 'ild )lants is longer 711, 108* A functional role of the Au2RIAA )roteins

III domain, 'hich is a )art of the am)hy)athic \WW+fold seuence similar t6 \+

ri((on multimerisation and &NA+(inding domain -&B& of the )rocariot Arc and

MetV re)ressor )roteins, has no' clearly (een esta(lished 71$=, 1;84 it is

suggested that this \WW+seuence is inoled in the dimeri:ationRmultimeri:ation

of Au2RIAA )roteins and heterodimeri:ation of Au2RIAA )roteins 'ith A@E

)roteins 711, 10, 18* @ecently, the function of the I domain -that maintainsthe Au2RIAA )roteins sta(ility, )roides their homodimerisation and ena(les

them t6 e2hi(it re)ressor functions has also (een studied4 at the same time, the

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)roteins, synthesi:ed in )lant )roto)lasts transformed (y A#8 genes, containing

medium domains rich in )roline or serine, e2hi(ited features ty)ical of

transcri)tion re)ressors, 'hile A@E0 + A@E= and A@E1# )roteins, )ossessing

domains rich in glutamine, 'ere transcri)tion actiators 71=8*

@ecently conducted genetic and )hysiological inestigations of

Arabidopsis 'ith / mutant A#839 A#85, andA#8= genes t6 esta(lished theirroles in the )lant au2in+controlled gro'th* It has (een sho'n that mono)terous

mp*ar45 mutations cause the termination of em(ryonic a2is formation and

ascular system deelo)ment 71=$8, 'hile np42*ar4= mutations cause the

distur(ance of arious mor)hogenesis stages 71=08* An im)ortant functional role

of the ?%%INRA@E/ transcri)tional factor, inoled in the mediation of the au2in+

regulated initiation of germ and floral organ gro'th in Arabidopsis, has (een

reealed 71=;, 1=8* It has (een found that ettin -ett mutations (ring a(out

)leiotro)ic effects on flo'er deelo)ment including an increase in the num(er of

)erianth and distur(ances in the re)roductie organs< differentiation* Some of theettmutant )henoty)ic features -for e2am)le, reduction of oary dimension are

similar t6 those of )inoid -pid and mono)teros -mp mutants + the au2in )olar

trans)ort of 'hich is distur(ed 71=$, 1==, 1=#84 on the (asis of this analogy it has

(een concluded that the au2in signal transmission is distur(ed as a result of ett

mutations*

Moreoer, the )henoty)ic features of 'ild+ty)e )lants, treated 'ith the

na)hthyl)hthalamic acid -NPA L a )olar au2in trans)ort inhi(itor, resulted ina

reduction of oary relatie t6 a)e2 of the )istil and to (asal internode -sti)e,

effectiely )henoco)ying au2in res)onse mutant ett, au2in signaling mutantpid,

and the au2in trans)ort mutant)in+formed 1 -pin1 71=; L 1=#8* %he data

o(tained suggested that the)77gene controls the oary deelo)ment inside the

gynoecium and its functional actiity de)ends on the au2in gradient 71=, 1#!8*

%he seuence analysis has ascertained that the ?%% )rotein -called A@E/

transcri)tional factor (elongs t6 the A@E )rotein family* .o'eer, unlike its

other mem(ers -)ossessing the III and IF C+terminal domains, )roiding their

heterodimeri:ation 'ith the Au2RIAA )rotein+re)ressors family, the ?%% )rotein

has one uniue C+terminal domain rich in serin and conseuently the )ossi(ility

of its heterodimeri:ation 'ith Au2RIAA )roteins is im)ossi(le 71/#, 1=, 1#18*

Eurther researches for modifiers of the ett mutant )henoty)e hae lead t6the identification of the S?USS -S)& gene regulating the e2)ression of the floral

homeotic gene AAM9US -A$ that encodes the MA&S+(o2 transcri)tional

factor controlling the homeotic transformation of )etals in mosaic car)els,

stamens, or se)als 71#"8* seu3 mutations hae (een ascertained to reduce

classical res)onses t6 e2ogenous au2in effects -such as a)ical dominance,

initiation of the lateral roots formation as 'ell as distur(ance of the leaf and flo'

'horl formation, 'ith dou(le ett= seu3 andpid1 seu3mutations synergetic

enhancement of mor)hological defects 'ere o(sered -ty)ical of ett and pid

mutants, resulting in a com)lete termination of the flo' deelo)ment 71=8*Based on the o(tained data it has (een concluded that S)& and)77genes are

res)onsi(le for the floral organs deelo)ment 5ointly controlling the au2in+

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regulated genes transcri)tion* 9n one hand, it is suggested that S?U links ?%%

'ith other regulatory molecules such as A@E andRor Au2RIAA )roteins, (ut, on

the other hand, the results of studies on the yeast t'o+hy(rid system gie )roof of

the interaction of floral S?U homologues only 'ith one transfactor L ?%%RA@E/

and the ina(ility of S?U t6 (ind, )articularly 'ith A@E1* Neertheless, since the

S)&and)77*A#83e2)ression is not tissue+s)ecific, i*e*, it is o(sered not onlyin flo'ers, (ut in many other )lant tissues and organs, the regulatory effect of

S?U and ?%%RA@E/ com)le2 on the Au2RIAA gene e2)ression, directly

inoling other transfactors, is still )ossi(le 71#, 1=;, 1=8*

No', there is no definite )roof that the re)ressie effect of Au2RIAA

)roteins result from their indirect (inding 'ith Au2@?s of )romoters au2in+

regulated genes 'ith )artici)ation &NA+(inding A@E4 on the contrary, there are

data su))orting the idea that Au2RIAA )roteins sho' their re)ressie effect

inde)endently 711, 1", 1=!8* Eor e2am)le, )roteins, encoded (y )lasmide

Au'*(AAgenes -for e2am)le,Au'++ and $01 genes of soy as 'ell as PS(AA2*5and PS(AA. genes of )ea, controlled (y a strong constitutie CaMF /0S

)romoter, may act inde)endently as transcri)tional re)ressors that re)ress the

transcri)tion of au2in+regulated re)orter genes in carrot transformed )roto)lasts

71=!8*

By a))lying arious genetic techniues -e*g, deletion analysis, linker+

scanning, site directed mutagenesis, and gain of function analysis Au2@?s

)romoter seuences of many au2in+regulated genes hae no' (een determined*

%he -% %CCCA% seuence has, for e2am)le, (een found in Au2@?s of

)romoters of )eaPS(AA*5genes, %%C%C seuence L in Au2@?s of )romoters

of soy C03genes and (oth kinds of )alindrome re)eats are )resent in Au2@?s of

)romoter of soy SAAgenes 71!, 11, 1=!, 1#/8* %he functional role of

these seuences has (een ascertained3 'ith a lo' leel of au2in Au2@?s re)resses

the transcri)tional actiity of close or remote constitutie elements of &NA and

ice ersa, an increase in the au2in leel causes a de+re)ression of the constitutie

elements of &NA and their actiation*

Another 'ell studied Au2@? of the )romoter au2in+induced gene is the

osc*as1element originally found in the Cauliflo'er Mosaic Firus -CaMF /0S

)romoter 71#$ L 1#8* %he as1 element, consisting of t'o im)erfect

%AC%CA )alindromes, has (een sho'n t6 mediate (oth salicylic acid+ andau2in+induci(le transcri)tion actiation 71#8* %he as1element 'as identified in

gene )romoters of arious )lants including the au2in+induced 7$AandPar genes

of to(acco 71#$ + 1#=8* %AC%CA )alindrome (inding 'ith the nuclear )rotein

ASE+1 com)le2 'as determined (y using electro)horetic mo(ility shift assay

71#08*

%he data that the regulation of e2)ression of genes 'hose )romoters

contain Au2@es of the as1 ty)e inoles trans+actiating factors, (elonging t6

the 7$Agenes family of )roteins, )ossessing (XIP -(asic leucine :i))er &B&

domain and called +(o2 (inding factors, hae also (een o(tained 71#;, 1#=,1##8* It has (een sho'n, for e2am)le, that in transgene )lants that )ossess genes

containing Au2@es of the as1 ty)e, the cis+elements and their trans+actiating

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factors dis)lay a tissue+s)ecific actiity during (inding 'ith )romoters of the

glutation+trans)herase -%S gene 7"!!8* %he trans+actiating factor of the

7$A1a to(acco gene has (een found t6 affect the transcri)tion of regulatory

genes containing Au2@?s of the as1 ty)e as a res)onse t6 2eno(iotic stress

factors3 a relatie num(er of 7$A transcri)ts is e2)ressed in roots and shoots,

correlating 'ith the as1+controlled (asal leel of the $&S transgene e2)ressionand 'ith t'o $7Sgenes* By means of the hy(ridi:ation in situ intact seedlings

hae (een found t6 e2)ress 7$A1a and $7Sgenes mainly in root to) meristems*

Similar data hae (een o(tained (y a genetic analysis ofP$13, a homologue of

the trans+actiating factor 7$A1a, and the assum)tion has (een corro(orated that

the t'o factors are )resent in the )rimary roots and their meristems, 'hich can

affect the isoen:yme e2)ression* It has (een ascertained that the )lant gene

e2)ression regulated (y the trans+actiating factor %A1a or (y its homologues,

inhi(ited (y $7S -$N71 and $N735 genes 'hose actiity is )otentiated (y

au2in through as1* %he 7$A 1aandP$13transcri)ts uantity is correlated 'iththe relatie (asal actiity of as1+regulated genes4 the au2in treatment enhances

this actiity more in shoots than in roots*

Among genes identified in recent years and 'hose e2)ression is )otentially

actiated (y au2in due to their )resence at Au2@?s -osc*as1ty)e there are also

theZ!1 gene of corn -encoding )roteins of )otassium channels,NAC1gene of

Arabidopsisand genes of mitogenic actiated )rotein kinases -MAPK of arious

)lants 71/#, "!1+ "!/8*

@esults of many studies indicate that, de)ending on its intracellular

concentration, the au2in affects the duration of life of Au2RIAA )roteins and their

a(ility t6 re)ress the transcri)tion of earlyR)rimary au2in+regulated genes* It has

(een sho'n, for e2am)le, that during an increase of the au2in concentration in

)lant cells transformed (y chimeric (AAL&Cgene, Au2RIAA )roteins (ecome

less sta(le as a result of marking N+end )roteins (y the target+chain of four

molecules of the )rotein u(iuitin consisting of ; amino acid residues

-discoered (y Professor Ale2andre arshasky of the California %echnological

Institute -USA (y means of the en:yme u(iuitin )rotein ligase* Su(seuently

u(iuitinated -i*e* associated 'ith u(iuitin Au2RIAA )roteins su(5ected t6

degradation in the )roteasome -consisting of t'o su(units L )roteolythic nuclear,

a molecular mass of a(out !! k&a and sedimentation coefficient of "!S, as )artof a more com)le2 )article haing a sedimentation coefficient of ";S and due t6

their re)ressing effect, regarding other au2in+regulated genes, is reduced 711,

"!$, "!08*

%he trans)ort of the Au2RIAA )rotein+re)ressors t6 the location of their

degradation -)roteasome has (een found t6 inole actie )rotein+en:ymes3

en:yme ?1 actiating the molecule of u(iuitin and coneying it t6 the

con5ugating en:yme ?", 'hich, in turn, transfers the actiated molecules t6 the

re)resentatie of the Jlacing en:yme family L t6 u(iuitin )rotein ligase ?/,

coalently Jlacing the u(iuitin chain t6 a )rotein+su(strate 7=#, "!;8* %here)resentaties of ?/ ligase in )lants are SCE+com)le2es -controlling

deelo)ment of floral organs, circadian clock actiity and cell res)onse to

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)hytohormones au2in and ABA consisting of four su(units3 Cdc0/ )roteins of

culline, )roteins encoded (y SKP1 and @BQ1 genes as 'ell as a (ig family of E+

(o2 )roteins 7"!8* %he E+(o2 )rotein function is t6 interact 'ith target )roteins

follo'ed (y their su(seuent degradation in ";S )roteasome* %he E+(o2 )rotein

actiity is controlled (y the SCE+com)le2 so that at first, one of the SCE+com)le2

com)onents + the )rotein culline interacts 'ith the @BQ1 )rotein and then aformed dimer com)le2 attaches the C+terminal domain of E+(o2 )roteins and

SKP1 )roteins -interacting 'ith the N+terminal domain E+(o2 )roteins act as a

link*

Presently, ?/ ligase SCE+com)le2 -called SCE%I@1 inArabidopsis, )laying

a leading )art in the Au2RIAA )rotein degradation, has (een identified and 'ell

descri(ed4 mutations in genes, encoding the SCE%I@1 ligase com)onents, reduce

the au2in res)onse in )lants 71", "!= + "1!8* %he SCE%I@1com)le2 com)osition

includes )roteins, encoded (yAtC&L19 AS1, orAS+and#B61genes, and the

E+(o2 )rotein encoded (y the 7(#1 -%rans)ort Inhi(itor @es)onse 1 gene*Mutations in AS1 or 7(#1 genes manifest themseles in some reduction of

res)onse t6 au2in and, ice ersa, during the 7(#1 gene hy)ere2)ression the

au2in+regulated gene e2)ression is enhanced 7"!=8* %he actiation of %I@1 E+

(o2 )rotein -res)onsi(le for degradation of Au2RIAA )roteins in )roteasome is

effected (y SCE%I@1com)le2 com)onents attaching to leucine+enriched seuences

of the %I@1 E+(o2 )rotein 71"8*

As mentioned a(oe, the desta(ili:ation site of Au2RIAA )roteins is the II

domain containing the seuence consisting from 1/ amino acid residues

-FFPPF@S@K L degron, the central region -PPF of 'hich is

reuired for the interaction of these )roteins 'ith the %I@1 E+(o2 )rotein*

Mutations in the II domain, )laying a central )art in Au2RIAA )roteins, hae (een

sho'n t6 decrease their a(ility t6 interact 'ith the SCE%I@1 com)le2 and t6

increase the sta(ility and functional actiity of these )roteins, re)ressing the au2in

signal transmission*

It has (een esta(lished that the SCE%I@1-?/+ligase com)le2 actiity may (e

regulated through )osttranslation modifications of AtCU>1 )rotein inoling

u(iuitin+like en:yme @UB14 mutations of genes, encoding AtCU>1 )rotein,

manifest themseles in defectie au2in res)onses* It has no' (een esta(lished

that the A6#1gene encodes one su(unit -N+terminal seuences of ?1 ligaseen:yme -actiating u(iuitin+like en:yme @UB1 similar t6 the ?N@") yeast

)rotein, 'hich is a com)onent of the )ath'ay actiely inoling the cyclin+

de)endent kinase inhi(itor + Sic 1) )rotein and 7(#1gene encoding E+(o2 )rotein

interacting 'ith Sic 1) )rotein 71;=8* Another su(unit -C+terminal seuences ?1

ligase en:yme is encoded (y)C#1 gene -?1 C+terminal related* It is su))osed

thatA6#1 and 7(#1genes regulate the meta(olism of different au2in+regulated

)roteins including )roteins inoled in the cell cycle*

It has (een esta(lished that ?" ligase encoded (y #C)1gene is res)onsi(le

for the formation of con5ugates of @UB1+cullin )roteins* %he results gie )roofthe com)onents of )rotein+ligase com)le2es ?1, ?", and ?/ can (e modificated

under coalent attachment of @UB1 )rotein 7=#, "118* It is found, for e2am)le,

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that @UB1 )rotein colla(orates 'ith U(a/) )rotein -containing amino acid

seuences that are identical to the C+terminal seuence of ?1 actiating en:yme

7"1"84 U(a/) form a com)le2 'ith ?nr") )rotein -containing amino acid

seuences, 'hich are identical to ?" en:yme )resenting in yeast e2)ressingA6#1

gene 7"!$84 the formation of con5ugates of @UB1+cullin )roteins is mediated (y

U(a1"), one of 1" ?"+like en:ymes, also identified in yeast 7"1"84 themodifications of Cdc0/) )roteins L cullins -'hich are com)onents of ?/ )rotein+

ligase com)le2 encoded (yAtC&L1gene, 'ith con5ugates of @UB1 )roteins, are

controlled (y A6#1gene -'hich encode ?1 ligase en:yme* It has (een sho'n

that mutations in genes, encoding com)onents of the ?/-SCEcdc$ com)le2, also

affect)N#+p9 Cdc53p9 Cdc2pand Scp1pgenes 7"!$8* %he a(oe+mentioned data

reeal the im)ortant role of u(iuitin+like en:yme @UB1 in )roteasome+mediated

destruction of )roteins in yeast*

SimilarA6#1+controlled )ath'ays of the au2in signal transmission are also

o(sered in )lants* Eor e2am)le, genetic analysis of Arabidopsis< mutant genes-encoding com)onents of u(iuitin+ligase com)le2 sho'ed that ?N@") )rotein

-encoded (y A6#1 gene interacts along the a(oe )ath'ay 'ith the Cdc$)

)rotein -E+(o2 )rotein, encoded (y the 7(#1gene 7=#, "!8, and mutant a'r1 and

tir1)lants are resistant t6 inhi(itors of the au2in )olar trans)ort and are im)erfect

in au2in+mediated )rocesses* &ata that a'r1and tir1 alleles interact synergetically

)roe that they are com)onents of the a(oe )ath'ay and com)ly 'ith the

o(serations concerning the distur(ance of normal )henoty)es in dou(le enr+

cdc2 mutants of yeast* Conseuently, it a))ears that A6#1 and 7(#1 genes,

inoled in the degradation of re)ressie Au2RIAA )roteins in the )roteasome,

follo'ed (y an actiation of the earlyR)rimary au2in+regulated gene family,

mediate au2in signals 7=#, 1!, 11, "!8*

Tne more com)onent of the com)le2 u(iuitinR)roteasome )ath'ay of

)rotein degradation has (een identified recently L a key re)ressor of the

)hotomor)hogenesis, such as C9P# signalosome, that is a multisu(unit

regulatory com)le2 -encoded (y the CSN gene family identified in arious

organisms3"rosophila, nematods, fungi, )lants, and humans 7"1/ L"1#8*

In )lants the C9P# signalosome 'as discoered, using a genetic analysis

of light+regulated seedlings of Arabidopsis, deelo)ing along t'o o))osite

)ath'ays such as )hotomor)hogenesis in light and scotomor)hogenesis orethyolation in darkness 7"1/, "18* %hese studies hae identified 11 locuses,

generally called )leiotro)ic C9PR&?%REUS -constitutieR)hotomor)hogenicR

deetiolatedRfusca genes, res)onsi(le for the scotomor)hogenesis 7"1/, ""! +

"""8* A re)ressie nature of cop*det*4us mutations reeals that COP*")7*8&S

genes encode )roteins L negatie regulators of )hotomor)hogenesis* It has (een

esta(lished that in cop*det*4us)lants, out of all isolated 11 alleles, eight locuses

-CSN1CSN: control the (iogenesis of the C9P# signalosome -'hose mutations

are )henoty)ically dis)layed in slo' gro'th in the early deelo)ment stages of

seedlings and in a lethal outcome at later stages 7""/8* Molecular+genetic studieshae sho'n that su(units of the signalosome CSN=, CSN, CSN$, CSN1, and

CSN/ -encoded (y COP;9 8&S59 COP:*8&S29 COP11, and 8&S11 genes,

"=


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res)ectiely e2ist e2clusiely in the form of the C9P# signalosome com)le2,

'hile CSN0ARCSN0B, CSN;ARCSN;B, and CSN com)onents may (e )resent

(oth as a com)le2 and as monomeric forms 7"1/, ""$, ""08*

A key )art in the disintegration of u(iuitin+la(elled )roteins in the

)roteasome is )layed (y CSN5 and CSN. genes encoding the family Mo/$

)roteins that are com)onents of the C9P# signalosome, elE/ com)le2 -containingelE/+)$ and elE/+)$! L factors of the translation initiation and ";S su(units of

the )roteasome in Arabidopsis7"1/, ""/8* According t6 the conducted seuence+

analysis, Mo/$ )roteins are diided into " classes* %he first class includes

)roteins CSN0 and @)n11 -su(unit ";S of the )roteasome com)le2*%he second

class includes )roteins CSN;, @)n= -su(unit ";S of the )roteasome com)le2 and

also elE/+)$ and elE/+)$! )roteins -su(units of the elE/ com)le2* %hese results

reeal that su(units ";S of the )roteasome and C9P# signalosome are

com)onents of the common )rotein com)le2 formed (y the t'o classes of the

Mo/$ )rotein family*A functional role of the C9P# signalosome in )lant gro'th and

deelo)ment regulation has (een ascertained (y means of genetic and

(iochemical techniues* %he C9P# signalosome is inoled in the )roteasome+

mediated degradation of )roteins -encoded (y P0


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9n the (asis of all a(oe+mentioned data, a hy)othetical scheme of the

au2in regulation of the gene e2)ression is )ro)osed -Eig* $* It consists of the

follo'ing 71/#, 1183 at the lo' concentration of IAA in )lant tissues and cells

the earlyR)rimary au2in+regulated genes -Au'*(AA9 $039 SA and ACS are

actiely re)ressed (y Au2RIAA )roteins -more sta(le at lo' concentrations of the

au2in* %he re)ression of au2in )rimary+regulated genes may )ro(a(ly resultfrom the heterodimerisation of Au2RIAA+re)ressors 'ith A@E transfactors L

transcri)tional actiators -similar t6 A@E0 + A@E= transfactors through the

common C+terminal III and IF domains and from a su(seuent interaction of the

formed com)le2 through glutamine+enriched N+terminal &B& -marked in the

diagram (y the letter of A@E transfactors 'ith site+targets -%%C%C

seuences of Au2@?s )romoters of earlyR)rimary au2in+regulated genes 7"/"8*

%hus heterodimerisation of Au2RIAA )roteins + transcri)tional re)ressors 'ith

transcri)tional actiators A@E re)resses stimulating influence of A@E

transfactors on e2)ression of earlyR)rimary au2in+regulated genes*Some increase in the au2in concentration results in a uick -during "+0

min dere)ressionRactiation of the earlyR)rimary au2in+regulated gene -including

Au2RIAA genes transcri)tion due t6 the dissociation of Au2RIAA and A@E

com)le2, su(seuent u(iuitination -i*e*, association 'ith )rotein u(iuitin of

Au2RIAA )rotein+re)ressors -)ro(a(ly also )hos)horylation of Au2RIAA )roteins

(y )hytochromes 71/8 designated in the diagram (y 7PhyA8 and degradation of

u(iuitinated Au2RIAA )roteins in the )roteasome 7"//8* %he attachment of

released A@E -through glutamine+enriched N+terminal &B& t6 %%C%C

seuences of Au2@?s )resent in )romoters of au2in+regulated genes causes

su(seuent actiation of these genes 'hich may (e )otentiated (y adding

additional transcri)tional actiators -(y means of dimerisationRmultimerisation

through the III and IF domains t6 A@E*

It has (een esta(lished that the e2)ression of Au'*(AA genes, many of

'hich contain %%C%C Au2@?s, also increases 'hen the IAA concentration

rises4 ho'eer, des)ite the fact that m@NA of Au2RIAA )roteins are actiely

translated, Au2RIAA )roteins (ecome unsta(le and are su(5ected t6 a uick

degradation (y the u(iuitinR)roteasome 'ay -if the au2in concentration remains

high* hen the IAA concentration decreases, the Au2RIAA )roteins

accumulation increases -due t6 the continuation of their m@NA traslation and'hen their concentration reaches considera(le leels, re)ressing Au2RIAA+

)roteins inhi(it their o'n e2)ression as 'ell as the e2)ression of other

earlyR)rimary au2in+regulated genes containing %%C%C Au2@?s 71/#, 118*

+onclusion. It should (e noted that the a(oe hy)othetical model of au2in

regulation of gene e2)ression is some'hat sim)lified since it does not define the

inolement of some molecular com)onents of the au2in signal )ath'ays

-(ecause they hae (een identified uite recently and their functions hae not yet

(een finally determined* Eor e2am)le, so far it remains uncertain as to ho'

transcri)tional re)ressors A@E -similar t6 A@E1 and A@E" mediate the au2inregulation of the gene e2)ression -e2)eriments on the t'o+hy(rid yeast system

hae sho'n that A@E1 is (ound e2clusiely 'ith Au2RIAA )roteins through the

/!


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common III and IF conseratie C+terminal domains and, at the same time, do

not interact 'ith the )roteins SAU@ and ./, )ossessing the same III and IF

domains 71#8* 9ne of the suggested mechanisms is that re)ressors A@E might

inhi(it gene transcri)tion similar Au2RIAA )roteins -i*e*, (y attaching A@E

transcri)tional re)ressors to A@E transcri)tional actiators and re)ressing their

actiation functions* %his model does not e2)lain the mechanism of com(inedregulating action of transcri)tion factors on gene e2)ression3 ?%%RA@E/

-dis)laying no a(ility for the heterodimerisation 'ith Au2RIAA+)roteins and

S?U -regulating the e2)ression of floral homeotic MA&S+(o2 transcri)tional

factor 71=8 since not all intermediate com)onents inoled in the )rocess hae

(een identified* So far there is no certainty as to if the au2in regulates the gene

e2)ression only (y dimeric A@E+Au2RIAA com)le2es -in com)liance 'ith this

model4 therefore, it is )ossi(le that higher multimeric A@E+Au2RIAA com)le2es

are inoled in the au2in+regulated )rocess* More detailed additional studies of

all of the a(oe )ro(lems 'ill undou(tedly su))lement and e2)and the list of)resently identified molecular com)onents inoled in the au2in signal

transmission*

'**'*N+*7

1* -ianco D? !?9 8lores 0? )? Control of root formation (y )lant gro'th

regulation* In %he Plant ro'th @egulators in Agriculture and .orticulture* @ole

and Commercial Uses R ?d* Amar5it S* Basra* + Ne' ork3 .a'orth Press, "!!!*

+ P* 1 + "0*

"*Arteca #? Plant ro'th Su(stances3 Princi)les and A))lications* + Ne' ork3

Cha)man and .all, 1##;* + "00 )*

/* Arteca #?.ormonal stimulation of ethylene (iosynthesis* In Polyamines and

?thylene3 Biochemistry, Physiology, and Interactions R ?d* .* ?* Elores, @* N*

Arteca, V* C* Shanon* + @ockille, M&3 American Society of Plant Physiologists,

1##!* L P* "1; + ""/*

$* -ogel D? P?9 ,oeste ? )?9 7heologis A?9 ieber D? D? @ecessie and dominant

mutations in the ethylene (iosynthetic gene ACS5 of Arabidopsis confers

cytokinin insensitiity and ethylene oer)roduction, res)ectiely RR Proc* Nat*

Acad* Sci* USA* L 1##=* L #0* L P* $;; + $1*0* "ehio C?9 $rossman ?9 Schell D?9 Schmulling 7? Phenoty)e and hormonal

status of transgenic to(acco )lants oere2)ressing the rol gene o4 Agrobacterium

rhizogenes %+&NA RR Plant Mol* Biol* L 1##/* L "/* L P* 11## + 1"1!*

;* Leopold A? C? Contem)lations of hormones as (iological regulators* In

.ormone Action in Plant &eelo)ment + a critical a))raisal R ?d* * F* .oad, V*

@* >enton* + >ondon3 Butter'orth and Co -Pu(lishers >%&, 1#=* + P* / + 10*

* Stoddart D? L* Biochemical considerations in deelo)mental studies* In

.ormone Action in Plant &eelo)ment + a critical a))raisal R ?d* *F* .oad, V*

@* >enton* + >ondon3 Butter'orth and Co -Pu(lishers >%&, 1#=* + P* "0 +"=;*

/1


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=* $ruenbaum


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"$*Lbler !?9 lGmbt "?Au2in+(inding )rotein from coleo)tile mem(ranes of

corn* II* >ocalisation of a )utatie au2in rece)tor RR V* of Biol* Chem*+ 1#=0 (* +

";!*+ P* #=0$ + #=0#*

"0*Lbler !?9 lGmbt "?9 Simon ?Au2in+(inding in target tissue RR V* of Cellular

Biochem* + 1#=;* + 1! B* + P* 11 + 1#*

";*earns A? ,?%he search for the au2in rece)tor* + &* Phyl* thesis, Uniersityof Ne' ork* )u(l*, 1#="* + ""= )*

"* Oostrom 0?9 ulescha Z?9 -an -liet 7?B?9 Libenga ?#?Characteri:ation of a

cyto)lasmic au2in rece)tor from to(acco+)ith callus RR Planta + 1#=!* + 1$#* + P*

$$ + $*

"=* !aan A?C?9 -an der Linde P?C?$?9 0arces P?A?A?9 Libbenga ?#?

Correlation (et'een the )resence of mem(rane+(ound au2in (inding and root

regeneration in cultured to(acco cells RR Planta* + 1#=0* + 1;$* + P* /; + /=*

"#* Zudi D? Increases in the ca)acity of )ea tissue to form acyl+as)artic acids

s)ecifically induced (y au2ins RR Ne' Phytologist *+ 1#;;* + ;0* + P* # + "1*/!* Zur4luh L?L?9 $uil4oyle 7?D? Au2in+ and ethylene+induced changes in the

)o)ulation of translata(le messenger @NA in (asal sections and intact soy(ean

hy)ocotyl RR Plant Physiol* + 1#=" ( + ;#*+ P* //= + /$!*

/1*BabaEo A?-? %he functions of fusicoccin+(inding )roteins in higher )lants RR

%hes* @e)* IF Internat* Conf* JPlant gro'th regulators, Mosco'* Pu(*3 Mosc*

State Agrar* Uni* + 1##*+ P*1!*

/"* -enis !?A?9 ,atson P?D? Naturally occurring modifiers of au2in+rece)tor

interaction in corn3 identification as (en:o2a:olinones RR Planta* + 1#=* + 1$"* L

P* 1!/ + 1!*

//* Aducci P?9 8ederico #?9 Ballio A* Eusicoccin rece)tors* ?idence for an

endogenous ligand RR Planta*+ 1#=!*+ 1$=*+ P* "!= + "1!*

/$*Bhatacharya ?9 Bis/as B?B? Induction of a high affinity (inding site for

au2in inAenaroot mem(rane RR Phytochemistry* + 1#="* + "1*+ P* /"0 + /$!*

/0* 7re/aas A?An au2in induces the a))earance of au2in+(inding actiity in

artichoke tu(ers RR Phytochemistry* + 1#=!* + 1#* + P* 1/!/ + 1/!=*

/;*NishiEuza


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$"*0asenstein ?0?9 )ans !?L?Calcium de)endence of ra)id au2in action in

mai:e roots RR Plant Physiol* + 1#=;* + =1* + P* $/# + $$/*

$/*night 0?9 Brandt S?9 night !?#* A history of stress alters drought calcium

signaling )ath'ays inArabidopsisRR Plant V* + 1##=*+ 1;*+ ;=1 + ;=*

$$*Zhang !?9 7anaEa 7?9 (Eura !?Calcium+induced conformational transition

reealed (y the solution structure of a)o calmodulin RR Nat* Struct* Biol* + 1##0* +"* + P* 0= + ;*

$0*ZielinsEi #?)?Calmodulin and calmodulin (inding )roteins in )lants RR Annu*

@e* Plant Physiol* Plant Mol* Biol* + 1##=* + $#* + P* ;# + "0*

$;* Dang 0?D?9 Pih ?7?9 ang S?$?9 Lim D?0?9 Din D?B?9 Piao 0?L?9 0/ang (?

Molecular cloning of a noel Ca"+(inding )rotein that is induced (y NaCl

stress RR Plant Mol* Biol* + 1##=* + /*+ P* =/# + =$*

$* $uerini "? Calcineurin3 not 5ust a sim)le )rotein )hos)hatase RR Biochem*

Bio)hys* @es* Commun* + 1##* + /* + P* =/# + =$*

$=* Shi D?9 im ?N?9 #itz O?9 Albrecht -?9 $upta #?9 0arter ?9 Luan S?9 udla D?Noel )rotein kinases associated 'ith calcineurin B+like calcium sensors in

Arabidopsis RR Plant Cell*+ 1###*+ 11* + P* "/#/ + "$!;*

$#*Liu D?9 Zhu D??A calcium sensor homolog reuired for )lant salt tolerance RR

Science*+ 1##=* + "=!*+ P* 1#$/ + 1#$0*

0!*)lliott "?C?9 Batchelor S?!?9 Cassar #?A?9 !arinos N?$?Calmodulin+(inding

drugs affect res)onses to cytokinin, au2in and gi((erellic acid RR Plant Physiol* +

1#=/* + "* + P* "1# + ""$*

01*elly $?D?Calcium, calmodulin and the action of )lant hormones RR %rends

Biochem* Sci* + 1#=$* + #* + P* $ + 0*

0"* 7anaEa 7?9 Ames D?B?9 0arey 7?S?9 Stryer L?9 (Eura !?Seuestration of the

mem(rane+targeting myristoyl grou) of recoerin in the calcium+fre

Documents

Signalling Pathways of Auxin