17:30 - 8:30, 2009 בפב רואר 18הפקולטה לחקלאות רחובות',אריוביץאולם

The symposium in sponsored in part by :The Manna Institute for Plant BioSciences at Tel Aviv University

הז מ נה ז ו מה ו וה א יש ור כנ י ס ה ב רכ ב לפ ק ול ט ה לח ק ל א ו ת

Http://www.tau.ac.il/lifesci/ispb

SCIENTIFIC PROGRAM 8:15 Registration and Distribution of Meeting Material 8:50 – 12:30 Morning Session 8:50 – 9:00 Opening Remarks:

Dean of the Faculty of Agriculture, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot

Efraim Lewinsohn Chair: Adi Avni, Tel-Aviv University 9:00 – 9:45 Plenary Lecture:

D1/d2 photosynthetic reaction center heterodimer: Regulation with a twist Meir Edelman, Weizmann Institute of Science

9:45 – 10:10 Evolutionary models of stress and variation Lilach Hadany, Tel Aviv University, Tel Aviv

10:10 – 10:25 Improving plant stress tolerance and yield production: is the tonoplast aquaporin sltip2;2 a key to isohydric toanisohydric conversion? Menachem Moshelion, Hebrew University of Jerusalem, Rehovot

10:25 – 10:40 Over-Expression of The Proline-Rich AtCWLP Forms a Cell Wall-Plasma Membrane-Cytosol Continuum that Improves Drought and Freezing Tolerance Arik Honig, Tel Aviv University, Tel Aviv

10:40 – 11:00 Coffee Break & Poster Viewing

Chair: David Weiss, Hebrew University of Jerusalem, Rehovot

11:00 – 11:25 Tissue identity shapes growth response to brassinosteroids

Sigal Savaldi-Goldstein, Technion, Haifa 11:25 – 11:40 EHD2 inhibits LeEix endocytosis and signaling

Maya Bar, Tel Aviv University, Tel Aviv 11:40 – 11:55 A dynamic maturation schedule underlies Arabidopsis leaf

development Idan Efroni, Weizmann Institute of Science

11:55 – 12:10 Interaction between class 1 homeobox (knoxi) genes and cytokinin

in plant development

Eilon Shani, Hebrew University of Jerusalem, Rehovot 12:10 – 12:25 Myosin dependent cellular movement of organelles and pathogens

Dror Avisar, Agriculture Research Organization, Bet Dagan 12:25 – 13:00 Lunch Break 13:00 – 14:00 Poster Session 13:45 – 14:00 ISPB meeting 14:00 – 17:30 Afternoon Session Chair: Dudy Bar-Tzvi, Ben Gurion University 14:00 – 14:25 Getting to grips with plant metabolism: state of the art, limitations

and the future of metabolic networks analysis Aaron Fait, Ben Gurion University, Beer Sheva

14:25 – 14:40 Strigolactones are new plant hormones that are involved in determination of plant architecture and plant interactions Hinanit Koltai, Agriculture Research Organization, Bet Dagan

14:40 – 14:55 Comparative functional genomics of ephedrine alkaloids biosynthesis in plants Raz Krizevski, Agriculture Research Organization, Newe Yaar

14:55 – 15:10 Intracellular compartmentalization is likely a major factor in directing flux of the MVA pathway in plants Maya Sapir-Mir, Agriculture Research Organization, Bet Dagan

15:10 – 15:25 Bypassing kinase activity of the tomato pto resistance protein with small-molecule ligands Dor Solomon, Tel Aviv University, Tel Aviv

15:25 – 15:45 Coffee Break & Poster Viewing

Chair: Tzion Fahima, University of Haifa 15:45 – 16:00 Micro-structures that enable hygroscopic movement in wheat awns

Rivka Elbaum, Hebrew University of Jerusalem, Rehovot 16:00 – 16:15 Specific AGPS are involved in stamen and pollen development and

function Dganit Richter, Ben Gurion University, Beer Sheva

16:15 – 16:30 Dissection of powdery mildew resistance uncover different resistance types in the triticum turgidum l. Gene pool

Roi Ben David, Inst. of Evolution, University of Haifa 16:30 – 17:15 Plenary Lecture:

Photosynthesis and protection against light stress Itzhak Ohad, Hebrew University of Jerusalem

Oral 1

-1-

D1/D2 PHOTOSYNTHETIC REACTION CENTER HETERODIMER:

REGULATION WITH A TWIST

Meir Edelman1 and Autar K. Mattoo2

1Department of Plant Sciences, The Weizmann Institute of Science, Rehovot, Israel 2U.S. Department of Agriculture, Agricultural Research Service, Sustainable Agricultural Systems Laboratory, Beltsville Agricultural Research Center, Beltsville, MD, USA

The D1/D2 heterodimer core is the heart of the photosystem II reaction center. A characteristic feature of this heterodimer is the differentially rapid, light-dependent degradation of the D1 protein. The D1 protein is possibly the most researched photosynthetic polypeptide, with aspects of structure–function, gene, messenger and protein regulation, electron transport, reactive oxygen species, photoinhibition, herbicide binding, stromal–granal translocations, reversible phosphorylation and specific proteases all under intensive investigation more than three decades after the protein's debut in the literature. The lecture will touch on some treaded areas of D1 research that have, so far, defied clear resolution, as well as cutting edge research on mechanisms and consequences of D1 protein degradation.

Oral 2

-2-

EVOLUTIONARY MODELS OF STRESS AND VARIATION

Lilach Hadany

Department of Plant Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel

Genetic variation provides the raw material for evolutionary change. In most population genetics models, variation is assumed to be generated at a uniform rate, depending on the genes coding for variation but not on the state of the individual. In this talk I discuss the implications of a new assumption - that the generation of genetic variation is itself plastic, so that genetic variation is generated at higher rates under stress. Using computational models, we found that stress-induced genetic variation can evolve under a wide parameter range, and might help explain the evolution of sex and the mechanisms of complex adaptation. Theoretical models and experimental evidence will be discussed.

Oral 3

-3-

IMPROVING PLANT STRESS TOLERANCE AND YIELD PRODUCTION: IS THE TONOPLAST AQUAPORIN SLTIP2;2 A KEY TO ISOHYDRIC TO

ANISOHYDRIC CONVERSION?

Menachem Moshelion1 Nir Sade1, Basia J. Vinocur2, Alex Diber2, Arava Shatil1, Gil Ronen2, Hagit Nissan1, Rony Wallach1,Hagai Karchi2 1Faculty of Agricultural, Food & Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel; 2Evogene Ltd, 13 Gad Feinstein St., Rehovot 76121, Israel; Anisohydric plants are thought to be more drought tolerant than isohydric plants. However, the molecular mechanism determining whether the plant water potential during the day remains constant or not regardless of the evaporative demand (isohydric vs anisohydric plant) is not known. Here, it was hypothesized that aquaporins take part in this molecular mechanism determining the plant isohydric threshold. Using computational mining a key tonoplast aquaporin, tonoplast intrinsic protein 2;2 (SlTIP2;2), was selected within the large multifunctional gene family of tomato (Solanum lycopersicum) aquaporins based on its induction in response to abiotic stresses. SlTIP2;2-transformed plants (TOM-SlTIP2;2) were compared with controls in physiological assays at cellular and whole-plant levels. Constitutive expression of SlTIP2;2 increased the osmotic water permeability of the cell and whole-plant transpiration. Under drought, these plants transpired more and for longer periods than control plants, reaching a lower relative water content, a behavior characterizing anisohydric plants. In 3-yr consecutive commercial glasshouse trials, TOM-SlTIP2;2 showed significant increases in fruit yield, harvest index and plant mass relative to the control under both normal and water-stress conditions. In conclusion, it is proposed that the regulation mechanism controlling tonoplast water permeability might have a role in determining the whole-plant ishohydric threshold, and thus its abiotic stress tolerance.

Oral 4

-4-

Over-Expression of The Proline-Rich AtCWLP Forms a Cell Wall-Plasma Membrane-Cytosol Continuum that Improves Drought and

Freezing Tolerance

Arik Honig1, Ellen Zuther2, Mohamad Abu-Abied3, Eddy Belausov3, Einat Sadot3, Aviah Zilberstein1

1 Department of Plant Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel. 2 Max Planck Institute of Molecular Plant Physiology, 14476, Potsdam-Golm , Germany. 3 Department of Ornamental Horticulture, The Volcani Center, Bet Dagan, 50250, Israel. The Arabidopsis thaliana proline-rich Cell Wall Linker Protein (AtCWLP), has been chosen as a model protein for estimating the role of proline-rich membrane proteins in stress tolerance. Bioinformatical analysis and CWLP::GFP localization results indicated that the CWLP has an external proline-rich N-terminal domain, three trans-cell membrane domains and a cytoplasmic protruding C-terminal end. Dehydration and freezing experiments showed that Arabidopsis plants over-expressing the CWLP or CWLP::GFP (CWLP-OE, or CWLP::GFP-OE) are more tolerant to water shortage and freezing temperatures compared to wild type (WT) plants. Water-shortage-tolerance was also confirmed in transgenic CWLP-OE potato. Plasmolysis experiments with detached leaves revealed that leaf cells of the CWLP-OE plants maintain normal cytoskeleton structure with no protoplast shrinkage (plasmolysis) during exposure to high osmoticum, whereas WT cells are plasmolyzed and their microtubule structure is collapsed. However, when the cytoplasmic-protruding domain or the cell wall anchoring proline-rich-part is missing, resistance to plasmolysis is lost, indicating that both the cell wall-anchored and cytoplasmic domains contribute to the CWLP function. Y2H split-ubiquitin assays, using the CWLP as a bait, identified interactions between AtCWLP and several cell membrane aquaporins, suggesting that AtCWLP may serve as a scaffold for aquaporin positioning in the cell membrane. Taken together, our results indicate the existence of a novel cell wall-plasma membrane-cytosol continuum, formed by the CWLP, which is required for increased tolerance to water- and cold-stress.

Oral 5

-5-

TISSUE IDENTITY SHAPES GROWTH RESPONSE TO BRASSINOSTEROIDS

Sigal Savaldi-Goldstein, Yael Hacham, Neta Holland and Sophie Nissani

Faculty of Biology, Technion, Haifa, 32000, Israel Organ growth depends on coordination between cell proliferation and postmitotic cell expansion. That phytohormone signaling pathways are key regulators of growth is well established but little is known about how their activity is interpreted by distinct cell types. To address this question we are using Arabidopsis roots as a system and perform local perturbation of growth via manipulation of brassinosteroids (BRs) activity. BRs primarily regulate cell expansion. However, we have found that BRs also control the number of cells present in the elongation zone of the root meristem. Interestingly, both cell number and cell expansion are differentially regulated by distinct tissues, thus exposing various levels of cell-cell communication occurrence. Supported by recent works, our results demonstrate that BRs, like other hormones, are acting in selected cells of the plant body to regulate organ growth and serve as a basis for investigating local BR interaction with additional hormone signaling pathways.

Oral 6

-6-

EHD2 INHIBITS LeEIX ENDOCYTOSIS AND SIGNALING

Maya Bar and Adi Avni Department of Plant Sciences, Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv,

Israel

Plants are constantly being challenged by aspiring pathogens. In order to protect themselves plants have developed numerous defense mechanisms both specific and non-specific to the attacker. Pattern recognition receptors can trigger plant defense responses in response to specific ligands / patterns. Bacterial flagellin triggers plant innate immunity via the FLS2 receptor, while EIX (ethylene-inducing xylanase) triggers a defense response via the LeEIX receptor. Endocytosis has been suggested to be crucial for the process in both cases.

We have isolated and characterized two Arabidopsis EH domain containing proteins (AtEHD1 and AtEHD2). EH domain containing proteins function as regulators of endocytosis through their ability to interact with other proteins involved in this process. We showed that the two proteins are involved in endocytosis in plant systems and demonstrate that the Arabidopsis EHD proteins function similarly to mammalian EHDs. Over-expression of AtEHD2 has an inhibitory effect on endocytosis. This was shown in connection with transferrin internalization in mammalian cells as well as FM-464 internalization in plant cells.

Here we show that AtEHD2 inhibits EIX-mediated signaling but not flg22 mediated signaling, suggesting that different endocytosis pathways are involved in the induction of plant defense responses.

Oral 7

-7-

A DYNAMIC MATURATION SCHEDULE UNDERLIES ARABIDOPSIS LEAF

DEVELOPMENT

Idan Efroni, Eyal Blum, Alexander Goldshmidt and Yuval Eshed

Weizmann Institute of Science, Department of Plant Sciences, Rehovot, Israel

Leaf development has been monitored chiefly by following anatomical markers. Analysis

of transcriptome dynamics during leaf maturation revealed multiple expression patterns

that rise or fall with age or that display age specific peaks. These were used to formulate

a digital differentiation index (DDI), based on a set of selected markers with informative

expression during leaf ontogeny. The leaf-based DDI reliably predicted the

developmental state of leaf samples from diverse sources and was independent of mitotic

cell division transcripts. When calibrated by informative root markers, the same

algorithm accurately diagnosed dissected root samples, revealing a maturation transcript

signature that is independent of cell type.

We used the DDI to characterize plants with reduced activities of multiple CINCINNATA

(CIN)-TCP (TEOSINTE BRANCHED 1, CYCLOIDEA, PCF) growth regulators. These

plants had giant curled leaves made up of small cells with abnormal shape, low DDI

scores and low expression of mitosis markers, depicting the primary role of CIN-TCPs as

promoters of differentiation. Out results suggest the existence of an underlying ordered

maturation schedule, or clock, whose timing is regulated by heterochronic factors, such as

the CIN-TCPs, and which permit the development of a flexible and robust leaf form.

Oral 8

-8-

INTERACTION BETWEEN CLASS 1 HOMEOBOX (KNOXI) GENES AND

CYTOKININ IN PLANT DEVELOPMENT

Eilon Shani, Osnat Yanai, Yogev Borko, Hadas Melnik, Yael Berger and Naomi Ori

The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of

Agricultural, Food and Environmental Quality Sciences, The Hebrew University of

Jerusalem, P.O. Box 12, Rehovot 76100, Israel.

Plant meristems retain morphogenetic capacity throughout life. Class I homeobox

(KNOXI) genes are expressed in the shoot apical meristem (SAM), and play central roles

in SAM function and leaf patterning. KNOXI proteins act in part through the regulation

of hormone levels. We found that KNOXI proteins positively regulate cytokinin

accumulation by activating the transcription of the Arabidopsis isopentenyl transferase 7

(AtIPT7) gene, which encodes a cytokinin biosynthesis enzyme. Downregulating the

expression of two Arabidopsis KNOXI genes, BP and STM, in specific tissues using a

synthetic microRNA (miRSTM/BP) enabled us to circumvent the stm severe seedling

lethal phenotype and examine the function of STM and BP later in development.

Expressing an IPT gene and miRSTM/BP through the same promoter resulted in a

suppression of the miRSTM/BP phenotype. Overexpression of IPT or KNOXI genes in

tomato leaves resulted in partially overlapping phenotypes that included reiteration of

leaflet formation. The phenotypes were strongly affected by the exact developmental

timing of the ectopic expression, suggesting that the developmental context strongly

influences KNOXI function. Down regulating cytokinin or KNOXI genes targets in

tomato resulted in a dramatic reduction in leaf complexity, suggesting that both KNOXI

and cytokinin are required for compound leaf development.

Oral 9

-9-

MYOSIN DEPENDENT CELLULAR MOVEMENT OF ORGANELLES AND

PATHOGENS

Dror Avisar1,2, Mohamad Abu-Abeid1, Eduard Belausov1, Valerian V. Dolja2 and Einat

Sadot1 1The Institute of Plant Sciences, The Volcani Center, Bet-Dagan 50250, Israel. 2 Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331.

Plant myosins are diverse molecular motors that possess a head domain that binds actin

and hydrolyses ATP and a tail domain that is involved in cargo binding. Plants have two

classes of myosins, XI and VIII, whose specific functions are poorly understood. Here we

present evidences for differential specific activities of myosins in both Arabidopsis

thaliana (A.t.) and Nicotiana benthamiana (N.b.). Dominant negative mutants, lacking

the head actin binding domain of all 17 annotated A.t. myosin’s and several N.b.

myosin’s were transiently expressed in leaf epidermal cells. By tracking and calculating

organelle velocities in the presence of each myosin we found that six out of the thirteen

XI class myosins, are involved in Golgi stacks, mitochondria and peroxisomes rapid

movement. VIII class myosins had no significant effects on organelle movement, but

were found to be involved in the peripheral targeting of the Beet yellows closterovirus

protein - Hsp70h and the virus cell to cell movement. The inhibitory mutated myosins did

not disrupt the actin network and did not arrest other actin dependent motility of both

chloroplasts and RFP-FYVE labeled particles.

Oral 10

-10-

GETTING TO GRIPS WITH PLANT METABOLISM: STATE OF THE ART,

LIMITATIONS AND THE FUTURE OF METABOLIC NETWORKS ANALYSIS

Aaron Fait

Ben-Gurion University of the Negev, Jacob Blaustein Insts. for Desert Research, French

Associates Institute for Agriculture & Biotechnology of Drylands, Midreshet Ben-Gurion,

84990, Israel.

The emergence of high-throughput phenotyping platforms, such as metabolomics, has

facilitated biochemical and molecular analysis at a previously unprecedented level. Studies

have been conducted on a wide variety of species, generating vast amount of data.

Nonetheless, the complexity of the relationship between gene expression and metabolite

content hampers our understanding of the structure, regulation and dynamics of the plant

metabolic network. Added to this are constrains of technology and method leading to a poor

translation of scientific knowledge into breeding strategies. The reconstruction of metabolic

networks depends on the capability to implement an appropriate analysis of the different

‘omics approaches individually and as a multidimensional integrated matrix. Classical

bioinformatics and multivariate statistics have been recently coupled with significant

advances in network-based methods to generate biologically meaningful hypotheses and

predictions from complex data. This combined approach reduces the dimensions of the

dataset and ease the interpretation of the response of the metabolic network to perturbation,

by deciphering the qualitative and quantitative interaction between its components. Metabolic

network analysis facilitates the correct representation of the biosynthetic reactions of the cell,

which is fundamental to improve crop yield stability and productivity and to help develop

new varieties and cropping systems better suited to the environmental and economic

challenges of the present era.

Oral 11

-11-

STRIGOLACTONES ARE NEW PLANT HORMONS THAT ARE INVOLVED IN DETERMINATION OF PLANT ARCHITECTURE AND PLANT

INTERACTIONS

Hinanit Koltai1, Evgenia Dor2, Joseph Hershenhorn2, Kaori Yoneyama3, Koichi Yoneyama3, Danny Joel2, Eduard Belausov1, Smadar Wininger1, Sivarama Lekalla1, Hagit Shealtiel1, Chatalie Bahattacharya1, Natalie Resnick1, and Yoram Kapulnik1

1Institute of Plant Sciences, Agricultural Research Organization (ARO), the Volcani Center, PO Box 6, Bet Dagan 50250, Israel 2Dept. of Phytopathology and Weed Research, Newe-Ya'ar Research Center, POB 1021, Ramat-Yishay, Israel 3Weed Science Center, Utsunomiya University, 350 Mine-machi, Utsunomiya, Japan

Strigolactones are considered as a new group of plant hormones, participating in determination of plant shoot branching and plant interactions. However, the manner in which strigolactones regulate plant architecture is still unknown. Strigolactones are suggested to be synthesized in roots, and to be derived from the carotenoid pathway. Here, we present evidences for a new biological role for strigolactones, as involved in determination of plant root architecture via regulation of root cell length, root cell number, and root cell cycle. Also, morphological analysis of shoots suggested a role for strigolactones in tomato shoot epical dominancy. Strigolactones were shown to be involved also as signaling molecules for two tomato interactions, with the parasitic plant Orobanche and with the symbiotic arbuscular mycorrhiza fungi; strigolactones induced Orobanche seed germination and mycorrhiza fungi hyphal branching. Also, a cross-talk between strigolactones and auxin pathways in controlling shoot and root architecture may be envisioned.

Oral 12

-12-

COMPARATIVE FUNCTIONAL GENOMICS OF EPHEDRINE ALKALOIDS BIOSYNTHESIS IN PLANTS.

Raz Krizevski1,3 , Einat Bar1 , Shimon Ben-Shabat2 , Yaron Sitrit3,

Jonathan Page4, Peter Facchini5, and Efraim Lewinsohn1

1Newe Ya’ar, ARO, Ramat Yishay, Israel. 2Faculty of Health Sciences, and 3The Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel. 4Plant Biotechnology Institute, National Research Council Canada, Saskatoon, SK Canada. 5Department of Biological Sciences, University of Calgary, Calgary, AL Canada. (1S)(2S)-Norpseudoephedrine, (1S)(2S)-pseudoephedrine, (1R)(2S)-norephedrine and (1R)(2S)-ephedrine are pharmacologically important phenylpropylamino alkaloids collectively known as ephedrine alkaloids. Two plants that belong to different families and taxonomically distant groups are known to accumulate ephedrine alkaloids, Ephedra spp. (Ephedraceae) a gymnosperm widely used in Chinese medicine and an angiosperm Catha edulis (Celastraceae), also known as khat. Khat leaves are traditionally chewed as a stimulant in the Middle East and Eastern Africa. Very little is known about the mechanisms by which plants biosynthesize these compounds. This project is aimed at establishing a solid comparative functional genomics platform to facilitate the study of the biochemical and molecular factors that direct the accumulation of ephedrine alkaloids in plants. Feeding experiments have demonstrated that both plants apparently utilize a similar biosynthetic pathway for the ephedrine alkaloid biosynthesis. Annotated EST databases have been established from which candidate genes in ephedrine alkaloid biosynthesis will be identified by functional expression.

Oral 13

-13-

INTRACELLULAR COMPARTMENTALIZATION IS LIKELY A MAJOR

FACTOR IN DIRECTING FLUX OF THE MVA PATHWAY IN PLANTS.

Maya Sapir-Mir, Anahit Mett, Eduard Belausov, Shira Tal-Meshulam, Ahuva Frydman, Einat Bar, Efraim Lewinsohn, David Gidoni, and Yoram Eyal

Institute of Plant Sciences, The Volcani Center, Agricultural Research Organization, Bet-

Dagan, Israel.

Isoprenoids play numerous vital roles in basic plant processes and are extracted from plants for a variety of applications. The potential benefits from isoprenoid metabolic engineering for improving plant traits and uses is a subject with increasing scientific and applied interest. In higher plants, two independent pathways located in separate intracellular compartments are involved in the biosynthesis of the universal isoprenoid precursors IPP and DMAPP. The MVA pathway, referred to as cytosolic, leads via IPP/DMAPP to FPP the precursor for sesquiterpenes, triterpenes, and sterols, whereas the plastidic MEP pathway leads via IPP/DMAPP to GPP and GGPP, the precursors for monoterpenes, diterpenes, and tetraterpenes. While the flux through the MEP pathway is high in some plant tissues and products such as monoterpenes are abundant, factors regulating flux and channeling of the MVA pathway may constitute limiting factors for high-level production of sesquiterpenes. We will present recent results suggesting that some of the MVA pathway biosynthetic enzymes are located in peroxisomes. In this context, we will discuss a potential role for peroxisomes in isoprenoid biosynthesis and new model for regulation of MVA pathway flux towards sterol vs. sesquiterpene biosynthesis by compartmentalization.

Oral 14

-14-

BYPASSING KINASE ACTIVITY OF THE TOMATO PTO RESISTANCE PROTEIN WITH SMALL-MOLECULE LIGANDS Dor Salomona, Arale Bonshtiena, Maya Mayrosea, Chao Zhangb, Kevan M. Shokatb and Guido Sessaa

aDepartment of Plant Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel. bHoward Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, USA.

The tomato (Solanum lycopersicum) protein kinase Pto confers resistance to Pseudomonas syringae pv. tomato bacteria expressing the AvrPto and AvrPtoB effector proteins. Pto specifically recognizes both effectors by direct physical interactions triggering activation of immune responses. We used a chemical genetic approach to sensitize Pto to analogs of PP1, an ATP-competitive small-molecule inhibitor. By using PP1 analogs in combination with the sensitized Pto (Ptoas), we examined the role of Pto kinase activity in effector recognition and signal transduction. Strikingly, while PP1 analogs efficiently inhibited kinase activity of Ptoas in vitro, they enhanced interactions of Ptoas with AvrPto and AvrPtoB in a yeast two-hybrid system. In addition, in the presence of PP1 analogs, Ptoas bypassed mutations either at an autophosphorylation site critical for the Pto-AvrPto interaction or at catalytically essential residues, and interacted with both effectors. Moreover, in the presence of the PP1 analog 3MB-PP1, a kinase-deficient form of Ptoas triggered an AvrPto-dependent hypersensitive response in planta. Thus, rather than phosphorylation per se, a conformational change likely triggered by autophosphorylation in Pto and mimicked by ligand binding in Ptoas is a prerequisite for recognition of bacterial effectors. Following recognition, kinase activity appears to be dispensable for Pto signaling in planta.

Oral 15

-15-

MICRO-STRUCTURES THAT ENABLE HYRGOSCOPIC MOVEMWENT IN WHEAT AWNS

Rivka Elbaum

The Hebrew University, The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Rehovot 76100, Israel

The dispersal unit of wild wheat bears two pronounced filaments called awns. The awns bend

as they dry and straighten in a damp environment. The hygroscopic movement is explained

based on the orientation of the cellulose fibrils that build the cell wall as follows. The stiff

fibrils are embedded in a soft hygroscopic matrix. When the cell wall dries, the matrix shrinks

but not the fibrils. Therefore, the cell wall contracts in a direction perpendicular to the fibril

orientation. Using X-ray scattering, scanning acoustic microscopy, and scanning electron

microscopy, we identified an active part that contracts as it dries and pulls the awn to a bent

position. In this part, parallel fibrils are arranged in rotated laminas that form a nano-scale

plywood construction. Water molecules absorbed by the matrix probably cause large

microscopic distortions by expanding neighboring layers in perpendicular directions. This

may explain the increased drying rate, as detected by thermal gravimetric analysis. The fast

reaction to changes in the ambient humidity allows the awns to bend and straighten even at

moderate conditions, providing the seeds with the locomotion they need to move along and

into the soil, on their way to successful sowing.

Oral 16

-16-

SPECIFIC AGPS ARE INVOLVED IN STAMEN AND POLLEN DEVELOPMENT AND FUNCTION

Dganit Richter, Bella Levitin, Shani Sa'adon and Moriyah Zik

Ben Gurion University of the Negev, Department of Life sciences, Beer Sheva, Israel

Arabinogalactan proteins (AGPs) are hydroxyproline-rich proteoglycans, found at the cell surface, being attached to the outer surface of the plasma membrane or bound to the cell wall, and can also be secreted from the cell. AGPs are widely distributed within the plant kingdom, expressed in a developmentally-regulated manner in different cell types and tissues. We have recently demonstrated that disrupting the expression of pollen specific AGPs, by point mutations or by activating anti-AGPs RNAi, resulted in male sterility in Arabidopsis through the inhibition of pollen tube growth. We are currently continuing to study the mechanism of AGPs function. First, we are analyzing their subcellular localization using constructs expressing the proteins' coding regions fused to florescence reporter proteins. Further, we are testing the importance of different protein regions and specific amino acids to confer correct subcellular localization and function. This is done by expressing the proteins harboring directed mutations in agp mutant plants and testing their subcellular localization and ability to rescue the mutant phenotype. In addition, we working toward applying the RNAi approach successfully implemented in Arabidopsis, to obtain male sterile tomato plants by downregulating the expression of tomato stamen/pollen specific AGPs.

Oral 17

-17-

DISSECTION OF POWDERY MILDEW RESISTANCE UNCOVER DIFFRENT RESISTANCE TYPES IN THE TRITICUM TURGIDUM L. GENE POOL

Ben David R1, Xie W1, Peleg Z1,2, Saranga Y2, Dinoor A2, Korol AB1 and T. Fahima1

1Dept.of Evolutionary and Environmental biology, Inst. of Evolution, Faculty of Science and Science Education, University of Haifa, Mt. Carmel, Haifa, 31905 Israel

2 The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel

Powdery mildew (Pm hereafter) caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici Em. Marchal (Bgt hereafter), is a foliar wheat disease resulting in yield losses. Two Triticum Turgidum L. spp. lines: G18-16 (T. turgidum ssp. dicoccoides) and Langdon (T. turgidum ssp. durum) were screened with a set of 42 Israeli Bgt isolates and were found to be resistant to 29 and 3 isolates, respectively. These lines were used to generate a single-seed descent recombinant inbreed line population. The 152 RILs were tested for Pm resistance with two contrasting isolates: (i) Bgt#15, collected from T. durum and avirulent on G18-16; (ii) Bgt#66, collected from T. dicoccoides and generating partial resistance response in Langdon. Genetic map was constructed using microsatellite, DArT (Diversity Array Technology) and CAPS (Cleaved Amplified Polymorphic Sequences) markers. Segregation ratio of the RIL population in reaction to Bgt#15 showed that the resistance in G18-16 is controlled by a single dominant gene which is located on the distal end of chromosome arm 7AL. Quantitative trait loci (QTL) analysis of the reaction to Bgt#66 revealed one major QTL on chromosome 1A (LOD 16) and additional four minor QTLs located on other chromosomes 1B, 2B, 3A and 7A.

Oral 18

-18-

NON-RADIATIVE CHARGE RECOMBINATION PROECTS PHOTOSYSTEM II AGAINST OXIDATIVE STRESS

Itzhak Ohad, Aaron Kaplan, Ziv Reich and Nir Keren The Hebrew University, Departments of Biological Chemistry (I.O.), Plant and Environmental Sciences (A.K. and N.O.), Jerusalem, and Weizmann Inst.of Science, Israel (Z.R). Light-induced oxidative stress inactivates PSII oxygen evolution and thus, carbon fixation by phototrophic organisms. Persistence of PSII activity of Microcoleus vaginatus, a cyanobacterium inhabiting biological desert crusts when exposed to high light intensities, indicates presence of an effective protection of PSII against ROS. Short time exposure (20 min) to light intensities higher than required to saturate persistent oxygen evolution triggers a reversible, extensive loss (85-90%) of PSII-radiative charge recombination, (responsible for generation of 1O2), measured as variable fluorescence (Fv, Fv/Fm) and thermo-luminescence (TL). Loss of radiative charge recombination is not inhibited by herbicides binding to PSII-QB site, indicating that reduction of plastoquinone or O2 are not involved. However, a significant up-shift of the PSII-QA redox potential as detected by TL measurements, inhibits radiative charge recombination, thereby lowering generation of singlet oxygen and related oxidative stress. We present a novel model whereby non-radiative charge recombination within PSII lowers photoinactivation under excess illumination. A possible reason why this photo-protective mechanism was apparently lost during the evolution from ancestor cyanobacteria to the higher plant chloroplast will be discussed.

19

Poster 1 BUNDLE SHEATH TRACHEID COMPLEXES ARE LIKELY TO REGULATE

WATER TRANSFER FROM XYLEM TO THE ATMOSPHERE

Arava Shatil and Menachem Moshelion The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of

Agricultural, Food & Environmental Quality Science The Hebrew University of Jerusalem, Rehovot 76100, Israel

Plant growth and development are dependent on the tight regulation of water uptake and transport across cellular membranes and tissues. During transpiration, water is transmitted through plants, and evaporated from the leaves to the atmosphere through the open stomata. In this process water must exit the xylem and cross the single cell layer of the bundle sheath tissue tightly surrounding the entire vascular tissue. Our objective was to measure the water permeability of those cells and assess their role in regulating of the whole plant transpiration. In this work, we extracted specifically labeled protoplasts from bundle sheath and mesophyll cells from Arabidopsis thaliana leaves and measured their osmotic water permeability (Pf) in optimal and in stress conditions induced by ABA. Our result shows a uniform Pf behavior for all the bundle sheath cells in all the leaf areas. These cells show a significantly lower Pf when compared to mesophyll protoplasts (6.3±1 versus 12.3±3 respectively) and unlike mesophyll protoplasts they significantly reduced their Pf to an extremely low Pf value (3.1±0.5) after treatment with 1M ABA. These results suggest a novel stress response mechanism in which the plant reduces its xylem water loss to the leaf in response to stress employing the unique structure of the bundle sheath tracheid complex. Poster 2

WILD ROCKET DIPLOTAXIS TENUIFOLIA MUTANT WITH IMPROVED STORABILITY OF CULINARY AND HEALTHY VALUES

Daniel Chalupowicz, Dalia Maurer, Alona Ovadia, Yelena Shahar-Ivanov, Zion Aharon, Nehemia Aharoni, David Kenigsbuch

Department of Postharvest Science of Fresh Produce, The Institute for Technology and

Storage of Agricultural Products, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

Wild rocket (Diplotaxis tenuifolia) with the common name of rucola belongs to Brassicaceae family and is native to Europe and western Asia. World-wide demand of rucola has increased due to the introduction of "ready to eat" fresh-cut -salads in most modern markets. In the last few years, more and more people have been introduced to the benefits of healthful food consumption containing a wide range of nutrients such as fibers, flavonoids and glucosinolates. In this study we show selection of a wild rocket mutant induced by EMS. This mutant has: i) Improved phenotypic characteristics such as appearance of the leaves: green dark and uniform shape: lanceolate and pinnatisect. ii) Delayed early flowering which facilitates crop handling during the seasons of bolting induction, autumn and spring. iii) Maintenance of postharvest quality for longer time compared to commercial cultivars, due to a delay in post harvest senescence processes and conservation of nutritional values.

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Poster 3 HIGH BORON STRESS IN TOAMATO

David A Szwerdszarf, Ahuva Vonshak, Moshe Silberbush, Micha Guy The Institutes for Desert Research, French Associates Institute �for Agriculture & Biotechnology of Drylands, Ben-Gurion University of the Negev, Sede Boqer Campus The tolerance to high boron (B) concentrations and the B-induced antioxidative response were studied in two cultivated tomato cultivars, a) Lycopersicon escullentum Mill (Lluta) from the Lluta valley; b) L. escullentum M82 (M82). The Lluta valley region, located in northern Chile, is characterized by high salinity and B concentrations. The tomato plants were grown hydroponically in 0.03 (control), 1 or 5 mM H3BO3 for 20 days. Results: in 5 mM B grown plants, much lower levels of lipid peroxidation and hydrogen peroxide levels were found in Lluta plants as compared with M82. Also, increased activities of key antioxidative enzymes were found in Lluta leaves, including: superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase. In contrast, decreased activities of these enzymes were determined in leaves of M82 plants grown under these conditions. Growth of Lluta plants in the presence of 5 mM B was only slightly decreased where that of M82 decreased by 50%. Lower leaf and root B- contents were found in Lluta plants as compared with M82 It is concluded that Lluta plants are B-tolerant while M82 plants are B-sensitiveIt that the B-tolerance of Lluta plants from the ability of these plants to limit leaf and root B contents and to upregulate the activity of key antioxidative enzymes. Poster 4 DISRUPTION OF A PLASTID NON-INTRINSIC ABC PROTEIN IN ARABIDOPSIS RESULTS IN THE HYPER-ACCUMULATION OF TRANSITION METALS AND IN

ABERRANT CHLOROPLAST STRUCTURES

Einav Shimoni*, Miriam Hassidim* and Nir Keren

The Alexander Silberman Institute of Life Sciences, the Department of Plant

& Environmental Sciences, the Hebrew University of Jerusalem, Israel. Plastids are the major sink for Fe in shoot tissues. The large Fe requirement is common to plastids and to their evolutionary progenitors, the cyanobacteria. Therefore, it was interesting to examine whether iron transport mechanisms are conserved throughout the evolution of photosynthetic organisms. We examined two plant orthologs of the cyanobacterial FutC protein, Fe transporter, AtNAP11 and AtNAP14. We analyzed insertional mutants in the genes encoding for these proteins. Both nap11/nap11 and nap14/nap14 plants exhibited severe growth defects. However, significant changes in transition metal homoeostasis where detected only in nap14/nap14. This mutant was found to be an extreme Fe hyper-accumulator, containing ~18 times more Fe in the shoot tissue than wild type plants. Smaller effects were observed for Mo, Zn and Cu. The increased shoot transition metal content was accompanied by a specific loss of chloroplast structures. Reducing the Fe concentration in the medium resulted in partial rescue of the mutant phenotype. Based on these results we propose that AtNAP14 plays an important role in plastid transition metal homeostasis. One possibility is that AtNAP14 is a part of a chloroplast transition metal transport complex.

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Alternatively, AtNAP14 function may be in regulating rather than in transporting transition metals. Poster 5 DEVELOPMENTAL CONTROL COMPONENTS OF BANANA FRUIT RIPENING

AND THEIR INTERACTIONS WITH ETHYLENE T. Elitzur1,2, E.E. Goldschmidt2, J. Giovannoni3, J. Vrebalov3 and H. Friedman1 1Dept. of Postharvest Science of Fresh Produce, ARO, The Volcani Center, Bet Dagan 50250, Israel; 2Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Kennedy-Leigh Centre for Horticultural Research, Faculty of Agriculture, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot, Israel; 3U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) Plant, Soil and Nutrition Lab and Boyce Thompson Institute for Plant Research, Cornell University, Ithaca, NY 14853, USA

Members of the MADS-box gene family are components of the developmental ripening program. In our study we have cloned from banana MADS-box genes (MaMADS1-6). The genes showed only low homology to tomato RIN, but nevertheless the expression patterns during ripening and in response to ethylene and 1-MCP suggest that some of these genes serve as regulators of ripening. MaMADS2, 4, 5 and to a lesser degree also MaMADS3 preceded increase in ethylene production, but coincided with CO2 respiration peak in the pulp. On the other hand, in the peel, the expression of the genes MaMADS1, 3 and to a lesser degree also MaMADS4 coincided with increase in ethylene production. 1-MCP applied at the onset of increase in ethylene production increased the levels of MaMADS4 and MaMADS1 in pulp, while it decreased MaMADS1, 3 in peel, suggesting that some of the genes only in pulp are negatively controlled by ethylene. Only MaMADS2 is neither induced by ethylene nor by 1-MCP, and it is expressed mainly in pulp. Results strengthen the hypothesis that ripening starts from the pulp and advances toward the peel and reveal the different MADS-box genes participating in the ripening programs of the peel and pulp. MaMADS2 is a major candidate for a master regulator of ripening in banana. Poster 6

IDENTIFICATION OF DROUGHT RESISTANT FRUIT TREE CULTIVARS

Susanna Feldman1, Irit Bar Ya'akov2, Doron Holland2, and Amram Eshel1

1Department of Plant Sciences, Tel-Aviv University 2Newe Ya'ar Research Center, Agricultural Research Organization

The aim of the research is to identify drought resistant fruit-tree cultivars by testing the characteristics of the xylem in young branches. Such laboratory tests will be much faster and cheaper than subjecting whole trees to drought stress in the field. The tests are based on measuring the loss of hydraulic conductivity of the xylem tissue under high water tension due to cavitation. As the soil becomes drier and the plant loses water, the tension in the xylem increases until the water column breaks. This leads to cavitation that causes embolism and loss of hydraulic conductivity of the xylem vessel. We use the "Cavitron" instrument which

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simulates this process in the laboratory. This method has been used in the past for identifying plants adapted to arid habitats. This is the first study that uses it for determining intra-specific differences. Branches of stone-fruit and apple cultivars from the National Deciduous Fruit Tree Collection orchard at Newe Ya'ar research Center, ARO. The relationships between water tension and xylem loss of hydraulic conductivity were expressed by the pressure that caused 50% loss of conductivity (PLC50). Varietal and seasonal differences were tested. Attempts were made to correlate xylem anatomical characteristics with its vulnerability. Poster 7

FUNCTIONAL ANALYSIS OF PROMOTER ACTIVITY OF SUGAR BEETNHX1 GENE

Guy Adler1, Eduardo Blumwald2 and Dudy Bar-Zvi1

1Department of Life Sciences, Ben-Gurion University, Beer-Sheva, Israel. 2Department of Plant Sciences, University of California, Davis, USA.

Expression of the sugar beet NHX1 (BvHNX1), encoding a vacuolar Na+/H+ antiporter, is highly induced by salt stress. A 2.5 kbp promoter sequence of BvHNX1 was cloned. Two 5’ serial deletions of the BvNHX1 promoter sequences fused to GUS were constructed. One contained the 5’ UTR and intron sequences within 5’ UTR, whereas the other series did not. GUS was assayed, both histochemically and enzymatically, in transgenic Arabidopsis plants containing single insertions. While BvNHX1 was expressed in most tissues; highest expression levels were observed in apical meristems, shoot and root vascular tissues and roots branching, but not in root tips. Application of salt-stress, osmotic stress or ABA doubled the BvNHX1 promoter activity. The 5’ UTR and intron are not necessary for expression levels and/or salt induction of the reporter gene. A 336 bp promoter fragment was sufficient to drive gene expression in a salt dependent way. The DNA sequence lacks ABRE and DRE, major cis-acting elements involved in ABA-dependent and ABA-independent regulatory pathways. A number of putative cis-acting elements were identified. To study if these cis-acting elements have a role in the salt-induced activity of this promoter, these sequences were mutated, introduced into Arabidopsis plants, and their activity were assayed. Poster 8

THE EFFECT OF SALINITY ON THE VEGETATIVE AND REPRODUCTIVE PHASES IN TRITICUM SP. AND IN AEGILOPS SP.

Hamutal Inbart-Pompan, Tamar Eilam, Amram Eshel

Department of Plant Sciences, Tel-Aviv University, Tel-Aviv, Israel

Salinity is one of the stress factors which limit wheat crops worldwide. We are looking for salinity resistance traits among wild members of the Triticeae. In previous experiments done in our lab we demonstrated the distinction between salinity resistance in the vegetative and the reproductive phases of the plant development. Only plants that will exhibit resistance in both phases will be useful for improving crop resistance. The current research focuses on the effect of salinity stress on vegetative growth as well as on pollination and grain filling. We have screened accessions of Aegilops kotschyi, A. sharonensis, A. longissima and Triticum

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dicoccoides from the Lieberman Germplasm Bank at the Institute of Cereal Crops Improvement, Tel-Aviv University for growth, ion content, and reproductive parameters. We identified six lines of the above species which have shown relative resistance. Embryos were found in seeds of all lines but only in resistant lines the endosperm was complete. In sensitive lines, the endosperm was only partly developed resulting in empty grains. In all lines, sodium and chloride ions were accumulated in the leaves but only low ion levels were found in the spikes. Two lines of A. kotschyi were the most salt resistant and will be subjected to further studies. Poster 9

INTRA SPECIFIC ANCIENT DIVERSITY OF SPLICING JUNCTION AND PROTEIN SURFACE AT THE WILD WHEAT LR10 CC AND LRR DOMAINS

Hanan Sela, Eviatar Nevo, Tzion Fahima

Department of Evolutionary and Environmental Biology, Institute of Evolution, Faculty of Science and Science Education, University of Haifa, Mt. Carmel, Haifa, 31905 Israel.

Wheat leaf rust resistance gene Lr10, a CC-NBS-LRR gene, was cloned and sequenced from 36 accessions representing 13 populations of wild emmer wheat collected in Israel. Diversity analysis of revealed that the highest nucleotide diversity (Pi) was in the CC domain, while the lowest diversity was in the intron region. The overall Pi was 0.022, while Pi for the coding regions was 0.031. This diversity was moderate relative to R-genes but very high relative to other wheat genes. The CC domain, the most diverse domain was subjected to positive selection. The LRR domain was relatively conserved, but had a hot spot of amino acid variation between two haplotypes in the ninth repeat, that is predicted to be solvent exposed. The same hot spot differed in an alternative splicing junction present in one haplotype while absent in the other one. Those two haplotypes are ancient and were found also in A genome species T. monococcum and T. urartu. Plants were tested for resistance to leaf rust isolate avirulent to Lr10 but no resistance was found. Poster 10

MELON GENETIC MAP HIGHLY ENRICHED WITH FRUIT EST MARKERS AND METABOLIC QTL

Harel-Beja Rotem1, Tzuri Galil1, Portnoy Vitaly1, Lotan-Pompan Maya1, Lev Shery1, Bar Einat1, Yeselson Yelena2, Libhaber Smadar E.1, Meir Ayala1, Cohen Shahar2, Dai Nir2,

Hofstede Rene4, Olier Marc5, Burger Joseph1, Tadmor Yaakov1, Sherman Amir2, Lewinsohn Efraim1, Schaffer Arthur A.2, Ori Naomi3 and Katzir Nurit 1

1Agricultural Research Organization, Newe Ya’ar Research Center, Institute of Plant Sciences, Ramat Yishay, Israel 2Agricultural Research Organization, Volcani Research Center, Institute of Plant Sciences, Bet Dagan, Israel 3Hebrew University, Faculty of Agricultural, Food and Environmental Quality Sciences, The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Rehovot, Israel 4Keygene NV, Business Park, Wageningen, Netherlands 5Syngenta Seeds S.A.S., Saint Sauveur, France

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Melon (Cucumis melo L.) is a highly polymorphic species comprising genotypes with fruits that accumulate different levels of soluble sugars, organic acids, pigments and aroma volatiles. In order to understand the relationship between metabolites and the genes associated with their synthesis and fruit quality attributes, we constructed a genetic map of melon, enriched for fruit traits, metabolic QTLs and markers developed for fruit ESTs. A recombinant inbred line (RI) population was developed from a cross between PI414723 (subspecies agrestis) and 'Dulce' (subspecies melo). Phenotyping was conducted using 99 RI lines over four seasons in two locations (Israel and the US). The map includes more than 700 (SSR, SNP and AFLP) markers, 210 of which were developed from fruit ESTs, including candidate genes belonging to major metabolic pathways. The map covers 1,222 centimorgans (cM) with an average of 2.7 cM between markers. QTL analysis of the fruit metabolic data mapped chromosomal regions involved in the accumulation of fruit metabolites including: sucrose, carotenoids and volatiles such as sesquiterpenes. Interestingly, genes that are involved in the metabolism of sucrose and carotenoids were mapped to different loci than the QTLs of these metabolites, while variation for sesquiterepenes was directly mapped to two sesquiterpene synthases. Poster 11 ANTIVIRAL ACTIVITY OF ETHANOL EXTRACTS OF FICUS BINJAMINA AND

LILIUM CANDIDUM IN VITRO.

Ludmila Yarmolinsky1, Michele Zaccai2, Shimon Ben-Shabat3, David Mills4 and Mahmoud Huleihel1.

1Department of Virology and Developmenral Genetics, 2Department of Life Sciences and Biotechnology Engineering, 3Department of Pharmacology, Faculty of Health Sciences, 4Albert Katz Department of Dryland Biotechnologies, The Jacob Blaunstein Institutes of Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel.

The antiviral activity of plant ethanol extracts against Herpes Simplex Virus -1 and 2 (

HSV-1, HSV-2) and Varicella-Zoster Virus (VZV) were investigated in vitro. The examined plants were Ficus binjamina, resistant to various plant viruses, and Lilium candidum, has a high susceptibility to plant viruses. Leaf extracts of F. binjamina inhibited all studied viruses, while its fruit extracts inhibited only VZV. L. candidum leaf extracts had no effect on VZV but strongly inhibited HSV-1 and slightly HSV-2. All extracts did not show significant cytotoxic effect on uninfected Vero cells even at a concentration as high as 250µg/ml (CC50 > 400 µg/ml). Most effective antiviral effect was obtained when extracts were added to cells at the time of infection, whereas partial inhibitory effect was observed when they were added post-infection. The selectivity index (SI= CC50 / EC50) of F. binjamina (980) was significantly higher than that of Acyclovir (700), the standard medicine used against HSV, and L. candidum (70).

There was an indirect evidence for strong interactions between the plant extracts and the viruses and weak interactions with the cell surface. It is suggested that plant extracts exerted their anti-herpetic effect mainly by blocking the virus access to the host cells.

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Poster 12 ACTIVATION OF THE PLANT PARP1 BY THE STRESS HORMONE ABA

Maayan Avram(1), Xiaohong Ma(1), Malca Cohen-Armon(2), Leonid Visochek(2), Nir Ohad(3),

Moran Oliva(3) and Nava Moran(1)

(1) The RH Smith Inst. of Plant Sciences and Genetics in Agriculture, The RH Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, (2) The Neufeld Cardiac Research Inst., Sackler School of Medicine, and (3)Dept. of Plant Sciences, The GS Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 69978 PARP (poly-ADPribose polymerase), a nuclear protein regulating DNA repair and transcription, has been shown in animal cells to respond to plasma-membrane- initiated signaling mediated by phosphoinositides (PIs) (1). Hypothesizing that such signaling occurs in plants, we assayed PARP1 activity in crudely isolated nuclei of Nicotiana tabacum cultured cells (NT1) in response to abscissic acid (ABA), using 32P protein labeling by 32P-NAD. The highly sensitive radioactive assay detected a distinct PARylation (poly-ADPribose polymerization) band at ~116 kD, about the size of tobacco PARP1 (2), but anti-humanPARP1 antibody detected only two much higher bands, possibly PARP1complexes - lacking PARP activity - with proteins inseparable by standard separation techniques. Short ABA treatment (25 M) of NT1 decreased PARylation in genetically altered NT1 cells with high levels of PtdInsP2 and InsP3 (High PIs) (3). In contrast, ABA increased PARylation in control NT1 cells. We attribute the decrease to a fast, ABA-signaled, IP3-mediated (4) PARP1 PARylation in the High PIs, which lowered the subsequent, "back-32P-PARylation" during 32P-NAD incubation, contrasting with the slower PARP1 activation by ABA in Controls, peaking only during the 32P-NAD assay. References: (1) Homburg et al., 2000, (2) Sun et al., 1999, (3) Im et al., 2007, (4) Ma et al., 2009. Poster 13

CHARACTERIZATION OF FLORAL TRANSITION IN LISIANTHUS (EUSTOMA GRANDIFLORUM)

Maya Lugassi-Ben Hamo and Michele Zaccai

Department of Life Sciences, Campus Bergmann, Ben Gurion University of the Negev, POB 356 Beer-Sheva 84105, Israel

Lisianthus (Eustoma grandiflorum) is an ornamental plant originating from US. Temperature plays a major role in the control of lisianthus growth and flowering, depending on the developmental stage of the plants. Transition from the vegetative rosette to reproductive stage is inhibited by high temperature, while higher temperatures after stem elongation accelerates flowering. In Israel, lisianthus production is directed to winter and spring, when production in Europe is reduced and prices are high. In order to decrease the temperatures at planting (during late fall), growers use shade nets. The objectives of the study were (1) investigate the effects of shade on lisianthus development, floral transition, flowering time and inflorescence quality; (2) to establish the lisianthus meristem proteome before and after floral transition.

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Planting time, largely mediated by temperature, has a strong effect on floral transition, while shade regime significantly affected the plant's yield and quality. Longest and heaviest shade treatments caused greatest delays in flowering and decreased yield. We used IPG Ready Strips (7 CM) MW 4-20% and SYPRO Ruby protein gel stain, in order to optimizing the two-dimensional polyacrylamide gel electrophoresis protocol for generate stage-specific primordia protein maps and isolate differentially-expressed proteins. Poster 14

MOLECULAR MECHANISMS OF EIX ELICITATION

Sharfman Miya, Maya Bar, Silvia Schuster, Adi Avni

Department of Plant Sciences, Tel-Aviv University, 69978 Tel-Aviv, Israel

Plant-microbe interactions involve numerous regulatory systems essential for plant defense against pathogens. An ethylene-inducing xylanase (EIX) of Trichoderma viride is a potent elicitor of plant defense responses. Structural analysis of the EIX (LeEix1 and LeEix2) receptors suggests that they belong to a class of leucine-rich repeat cell-surface glycoproteins with a signal for receptor-mediated endocytosis. Both receptors are able to bind EIX while only LeEix2 transmits the signal for HR induction. The main purpose of the present work is to investigate the molecular mechanisms which allow plants to specifically activate defense responses after EIX elicitation. The brassinosteroid coreceptor, BAK1 (SERK3) was found to be involved in defense signaling through the flagelin receptor. Plant responses to flagelin were found to require the involvement of BAK1, as a BAK1 knock-out mutant was impaired in flagelin responses. Our results demonstrate that BAK1 binds LeEix1 but not LeEix2 in yeast two hybrid and bimolecular fluorescence complementation assay. We have recently found that LeEix1 attenuates EIX induced signaling responses. Interestingly, in BAK1 silenced plants, LeEix1 was no longer able to attenuate plant responses to EIX. Lipids are critical components of plant cell membranes and have been previously shown to play important role in various plant defense responses. N-Acylethanolamines (NAEs) are lipids found in both plants and animals. NAEs are derived from the hydrolysis of the membrane phospholipids and involved in endocannaboid signaling. In plants, NAE levels' are known to increase significantly within minutes post elicitation. We have found that, addition of NAE to tobacco cell suspension/plants treated with EIX inhibited elicitor-actived cell death. Furthermore, overexpression of tomato FAAH (NAE hydrolase) stimulated defense responses. Sharfman Miya and Bar Maya contributed equally to this work.

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Poster 15 DUAL ROLE OF THE WATER/CO2 AQUAPORIN, NTAQP1, IN REGULATING

STRESS-TOLERANCE MECHANISMS IN PLANTS

Nir Sade1, Michaele Gebretsadik1, Ron Seligmann1, Amnon Schwartz1, Rony Wallach2 and Menachem Moshelion1

1The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, and 2Department of Soil and Water Sciences The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100 Effective water transport via living cells is controlled by water channel aquaporin (AQP) activity. The tobacco AQP, NtAQP1, has been reported to facilitate CO2 permeability of mesophyll cells and has been suggested to regulate root hydraulic conductivity. Moreover, under abiotic stress, its expression level in the roots is significantly increased. In this study, we investigated the role of NtAQP1 in water and CO2 balance in whole tomato plants under optimal and abiotic stress conditions. Overexpression of NtAQP1 in tomato plants (SlNtAQP1) revealed a significant increase in whole-plant transpiration rate relative to controls, under both normal and abiotic stress conditions. In addition, SlNtAQP1 plants had larger stomatal aperture and a higher rate of CO2 assimilation, leading to higher fruit yield of these plants under all tested conditions. Reciprocal grafting of SlNtAQP1 and control plants revealed higher CO2 assimilation rates under salt stress only when the scion expressed SlNtAQP1. However, higher transpiration rate was not measured in any of the reciprocally grafted plants. Moreover, under salt-stress treatment, SlNtAQP1 plants exhibited higher root conductivity than control plants. The higher transpiration rate maintained by SlNtAQP1 plants could expose them to embolism damage, particularly under stress conditions. We suggest that by maintaining high root hydraulic conductivity under stress, SlNtAQP1 plants regulate their whole-plant water conductivity, resulting in improved abiotic stress tolerance. Poster 16

ISOLATION, STRUCTURE ELUCIDATION AND EVALUATION OF ANTI CANCER ACTIVIY OF STEROIDAL SAPONINS FROM BALANITIES

AEGYPTIACA Noa Goldschmidt1, Shimon Ben-Shabat1, Zeev Wiesman2 and Bishnu P. Chapagain 2

1Faculty of Health Sciences, Department of pharmacology and 2 Phyto-lipid biotechnology laboratory, Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel. Balanites aegyptiaca Del. Popularly, known as the desert date, is a spiny, evergreen tree commonly grown in the arid regions of Africa, the Middle East, and South Asia. B.Aegyptiaca extracts consider having high concentrations of steroidal saponins that contribute to the molluscidal, antidiabetic, anathematic, antiseptic, antiviral and anti cancer activities. Three steroidal saponins were isolated from the methanol extracts of B. aegyptiaca roots using chromatographic and spectroscopic methods. The structure of the main saponin that was isolated from the roots extract was elucidated by LC-ESI-MS and found to have the molecular ion of [M+H]+ m/z 1017. The anti cancer activity of the isolated saponin was evaluated against various human cancer cell line (Prostate cancer (LNCaP) and breast cancer

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carcinoma (MCF7)) in vitro and compared to a known relative saponin, Dioscin, that used as a positive control. The results showed potent antiproliferative activity of the isolated saponin in comparison with Dioscin the positive control.

Poster 17 GENETIC CONTROL OF SHOOT DEVELOPMENT IN PEPPER AND

COMPARATIVE ANALYSIS TO HOMOLOGOUS MUTATIONS IN TOMATO Oded Cohen1, Tomer Elitzur1, Yelena Borovsky1, Yuval Eshed2 and Ilan Paran1 1Volcani Center, Institute of Plant Sciences, Agricultural Research Organization, Israel. 2Weizmann Institute of Science, Department of Plant Science, Rehovot, Israel. Pepper and tomato are both closely related Solanaceae species with sympodial shoot development. In pepper, each sympodial unit consists of two leaves and a single terminal flower, while in tomato each unit consists of three leaves and an inflorescence. We studied mutants impaired in homologous genes affecting growth habit in both species. We found that fasciculate (fa), a pepper mutation characterized by “determinate” growth is homologous to self pruning (sp) in tomato that causes precocious termination of sympodial shoots. While the function of SP is to suppress sympodial flowering, the function of its homolog in pepper is to promote sympodial shoot elongation. A new pepper mutant, late flowering (lfl), is disrupted in the homolog of tomato JOINTLESS, where it is required for normal inflorescence development. Similarly to JOINTLESS, LFL acts to suppress vegetative growth in the inflorescence meristem. However, in tomato JOINTLESS is also necessary for the formation of abscission zone in the flower pedicel, while in pepper LFL promotes flowering in the primary and in the sympodial shoots. Furthermore, multiple flowers developed in lfl, indicate that the single flower in pepper is a reminiscence of an inflorescence and that LFL along with other factors controls the early termination of the inflorescence meristem. Comparative analyses of homologous mutations in pepper and tomato allow uncovering common and unique functions of homologous genes controlling diversification of shoot architecture in the two species.

Poster 18

ISOLATION OF A LeFW2.2 HOMOLOG IN ‘HASS’ AVOCADO: REGULATION OF ITS EXPRESSION RELATED TO REDUCED CELL DIVISION AND TO

SMALL FRUIT PHENOTYPE.

Revital Rosenfeld, Yardena Dahan and Vered Irihimovitch Volcani Center, Horticulture Department, Bet-Dagan, Israel

‘Hass’ cultivar (Persea americana Mill) produce two populations of fruits; normal (NF) and phenotypically small fruit (SF). Notably, even under favorable conditions, a high portion of SF is produced, contributing to economic losses. SF growth is limited by cell number and not by cell size, indicating that events controlling cell division play a key role in fruit size determination. In tomato, FW2.2 is one of few QTLs controlling fruit size. Cloning of FW2.2 revealed its effect is caused by a single gene (Lefw2.2) encoding a transmembrane-protein proposed to function as negative regulator of fruit cell division. In this study, a full-length

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cDNA (Pafw2.2) encoding a FW2.2-like protein was isolated from SF mesocarp tissue. The identified Pafw2.2 encodes a predicted 180 AA protein, sharing 62% identity with Lefw2.2 and has two predicted transmembrane domains. Sq-RT-PCR analysis revealed that the transcript level of Pafw2.2 strongly increased at phase II of fruit development, in different SF tissues, as compared to NF. During fruit development, mesocarp cell number was significantly higher in NF, yet, no significant differences in cell area between NF and SF were observed. Our results suggest that Pafw2.2 might function in similar fashion as Lefw2.2. Future exploration of Pafw2.2 function is called for. Poster 19

THE ROLE OF THE SIP1 AQUAPORINS SUBFAMILY IN CONTROL OF ENDOPLASMIC RETICULUM OSMOTIC HOMEOSTASIS.

Sefi Geva and Menachem Moshelion

Institute of Plant Sciences and Genetics in AgricultureThe Robert H. Smith

Faculty of Agriculture, Food and Environment The Hebrew University of Jerusalem. Rehovot, Israel

Aquaporins (AQPs) are trans-membranal proteins which have an important role in controlling water movement via plant membranes. SIPs are considered the smallest AQP subfamily with exceptional structure expressing only in multi-cellular plants. Its cellular localization was suggested to be at the rough endoplasmic reticulum (r-ER), yet this information was concluded based on single protoplast transient expression. Considering its absence in the unicellular organisms we assume that SIPs might regulate water balance mechanism in multi-cellular plants. In order to define the role and localization of those proteins in higher plants we expressed SIP1s proteins labeled with eGFP in Arabidopsis plants and cell suspension under the constitutive promoter 35s. The localization pattern of the fused proteins resembled the ER pattern as could confirm with the florescent marker ER-Tracker™ Red, yet limited in its extent. Our results support the suggested ER localization of the SIP subfamily, and provide a stable expression model system to track in vivo localization changes of SIPs in a living multi-cellular culture under normal and stress conditions. Poster 20

ROOT RESPIRATION IN RESPONE TO HIGH SOIL TEMPERATURE AND COMPETITION

Shimon Rachmilevitch

Ben Gurion University, Blaustein Institutes for Desert Research, Midreshet Ben

Gurion, Sede Boqer, Israel

Respiration is a major carbon metabolism process. The current paper presents two different studies that examined root respiratory characteristics associated with high soil temperature and root competition.

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In the first study we examined two Agrostis species: thermal Agrostis scabra, and A. stolonifera. Roots of both species were exposed to high or low soil temperature. Root respiration rate, alternative respiration, specific respiratory costs and the acclimation potentials were significantly different between the two species. The results suggest that acclimation of respiratory carbon metabolism plays an important role in root survival of Agrostis species under high soil temperatures and is related to the capacity to control rates and increase efficiency by lowering maintenance and ion uptake costs.

The second study examined the effects of self/non-self root competition with neighboring plants on root respiration. Roots of pea (Pisum sativum) plants were grown either with split roots (Non self) or without (self) for three weeks. Root respiration increased close to 20% in the non self plants as compared to the self plants.

The studies presented elucidate the importance of root respiration and provide a comprehensive understanding of the role of carbon metabolism in stress adaptation and acclimation to high soil temperature and competition. Poster 21

TOMATO ASR1 ABROGATES THE RESPONSE TO ABSCISIC ACID AND GLUCOSE IN ARABIDOPSIS BY COMPETING WITH ABI4 FOR DNA BINDING

D. Shkolnik and D. Bar-Zvi

Department of Life Sciences, Ben-Gurion University, Beer-Sheva 84105, Israel

Tomato ASR1 (SlASR1) encodes a water-stress, water-stress and ABA regulated plant-specific, highly charged protein. ASR1 is localized both in the nucleus and cytosol. ASR1 possess sequence specific Zn2+-dependent DNA binding activity. Cytoplasmic ASR1 was suggested to have chaperone-like protein protective activity. No ASR1 homologs were found Arabidopsis thaliana. SlASR was expressed in transgenic Arabidopsis under the control of CAM 35 S promoter. Over expressing SlASR Arabidopsis was found to display an abi insensitive4 (abi4)-like phenotype. Quantitative PCR analysis indicated that the expression of ABI4 that is known to be auto regulated, as well as downstream genes regulated by it (ABI5, lea genes) is significantly decreased in the ASR1-OE plants. Electro Mobility Shift Assay (EMSA) confirmed that ASR1 protein is capable of binding the CE motif in the ABI4 promoter DNA sequence. In vivo chromatin immunoprecipitation (ChIP) assay showed that ASR1 is bound specifically to ABI4 and not to other ABI regulated gene promoters. We thus suggest that the overexpressed ASR1 binds the ABI4 binding sites in ABI4 regulated gene promoters, and thus decreases the expression of ABI4 regulated genes such as ABI5 and ABI4 itself. (Shkolnik and Bar-Zvi (2008) Plant Biotechnology Journal 6, 368–378).

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Poster 22 AT THE CROSS ROADS BETWEEN IRON METABOLISM AND OXIDATIVE

STRESS

Sigal Shcolnick1, Lilia Reytman1 and Nir Keren1

1 The Alexander Silberman Institute of Life Sciences, Department of Plant and Environmental Sciences, Hebrew University, Givat Ram, Jerusalem 91904, Israel Iron is an essential nutrient for the survival of all organisms. However, the same redox properties that make iron a valuable cofactor also lead to oxidative interactions resulting in the formation of harmful radicals. Therefore, iron accumulation in the cells is tightly regulated to ensure that very little free iron is present. Synechocystis PCC 6803 contains two ferritin type storage complexes, bacterioferritin and MrgA. The physiological role of MrgA was studied using three disruption mutants: ΔmrgA, ΔBfrAΔBfrB, and ΔBfrAΔBfrBΔmrgA. Deletion of the mrgA gene did not impair the Fe storage capacity. On the other hand, a considerable slow down in the growth rate of ΔmrgA cultures was observed upon transfer from Fe replete to Fe depleted medium, indicating impeded utilization of the plentiful intracellular Fe. The survival of ΔmrgA cells after H2O2 treatment was impaired as compared with wild type, unlike that of ΔBfrAΔBfrB which has 50% of cellular Fe quota. Net 18O2 consumption was higher in ΔmrgA as compared to wild type, which could indicate a higher rate of Fenton reactions. Based on these results, we suggest that MrgA plays an important role at the cross roads between iron metabolism and the reaction to oxidative stress. Poster 23

IDENTIFICATION OF DROUGHT RESISTANT FRUIT TREE CULTIVARS

Susanna Feldman1, Irit Bar Ya'acov2, Doron Holland2, and Amram Eshel1

1Department of Plant Sciences, Tel-Aviv University 2Newe Yaar Research Center, Agriculture Research Organization

The aim of the research is to identify drought resistant fruit-tree cultivars by testing the characteristics of the xylem in young branches. Such laboratory tests will be much faster and cheaper than subjecting whole trees to drought stress in the field. The tests are based on measuring the loss of hydraulic conductivity of the xylem tissue under high water tension due to cavitation. As the soil becomes drier and the plant loses water, the tension in the xylem increases until the water column breaks. This leads to cavitation that causes embolism and loss of hydraulic conductivity of the xylem vessel. We use the "Cavitron" instrument which simulates this process in the laboratory. This method has been used in the past for identifying plants adapted to arid habitats. This is the first study that uses it for determining intra-specific differences. Branches of peach, plum and apple cultivars from the National Fruit Tree Collection orchard at Newe Yaar research Center, ARO. The relationships between water tension and xylem loss of hydraulic conductivity were expressed by the pressure that caused 50% loss of conductivity (PLC50). Varietal and seasonal differences were tested. Attempts were made to correlate xylem anatomical characteristics with its vulnerability.

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Poster 24 PCD IS INVOLVED IN THE ABSCISSION PROCESS

Tal Bar1, Shimon Meir1, Martin B. Dickman2, Sonia Philosoph-Hadas1, Shaul Burd1, Lilian

Sonego1 and Amnon Lers1

1ARO, the Volcani Center, Dept. of Postharvest Science of Fresh Produce, Bet Dagan, Israel 2 Dept of Plant Pathology & Microbiology, Texas A&M University, College Station, Texas,

USA Abscission of leaves, flowers or fruits occurs in the abscission zone (AZ). It is well known that hydrolytic enzymes have a central role in the process. Previously we have demonstrated that inhibiting the expression of the senescence and PCD-associated LX ribonuclease gene resulted in retardation of abscission in tomato. This novel finding led us to hypothesized programmed cell death (PCD) is involved in abscission. The presented experimental results provide evidence supporting the occurrence of a PCD process around the tomato AZ following induction of abscission during the late stage of the process. We observed cell death in the AZ as revealed by Evans Blue staining, activation of nucleases and proteases enzymes, as well as, induction of their encoding genes, accumulation of reactive oxygen species (ROS) in the AZ paralleled by induction of the NADPH oxidase gene and induction of PCD-associated genes including Metacaspase1 and Le-pirin. Furthermore, we observed a delay of abscission in plants over-expressing the anti-apoptotic gene sfIAP. These results suggest that the occurrence of PCD is required for normal progression of abscission in tomato. Poster 25 THE ROLE OF GDSL-LIPASES IN ARABIDOPSIS PETAL DEVELOPMENT AND

FUNCTION Tamar Rosilio-Brami, Bella Levitin, Dr. Moriyah Zik

Life Sciences Department, Ben-Gurion University of the Negev, Beer Sheva, Israel

GDSL-lipases are a subfamily of lipases – hydrolytical enzymes catalyzing the processing of complex lipids. The GDSL-lipase family is a very large gene family in plants, however thus far, the function of only few members has been suggested. Microarray and bioinformatical analyses revealed that different members are differentially expressed in various organs of the plant, including 15 genes that are predominantly or specifically expressed in Arabidopsis petals. These findings indicate their possible involvement in petal development and/or function. GDSL-lipases role in organ development and/or function might entail changes in lipid flux in the cell, which in turn may affect cuticle and/or membrane processing. Alternatively, they might participate in signal transduction pathways by producing lipid secondary messengers. In order to elucidate GDSL-lipases unique and common roles in petals, we initiated a detailed study of their expression pattern, demonstrating that several genes are expressed in late stages of petal development through the proximodistal axis, presumably restricted to the epidermal layer and its specialized cells. In parallel, we are conducting phenotypic analyses of petal GDSL-lipases mutant lines, including the use of light and electronic microscopy and biochemical tools to compare lipid profile and cuticle structure between wild-type and mutant plants.

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Poster 26

GERMINATION AND SEEDLING SURVIVAL IN NACL SOLUTIONS AFTER DESICCATION OF SOME HALOPHYTES FROM THE SOLONCHAK SALINITIES

OF THE KYZYLKUM DESERT IN UZBEKISTAN Tanya Gendler, Yitzchak Gutterman, Japakova Ulbosun and Nicolai Orlovsky. Jacob Blaustein Desert Research Institutes, Ben-Gurion University. Seeds of four species, of the Chenopodiaceae family, inhabiting the salinities of Kyzylkum desert in Uzbekistan; Haloxylon aphyllum, Salsola dendroides, Kochia scoparia and Kochia prostrata, were tested for their seed germination and seedling survival after periods of desiccation. The seeds were tested for germination in distilled water as well as in solutions of up to 3% NaCl. The seeds germinated well in solutions of up to 2% NaCl, but none germinated in 3% NaCl. After wetting for 24 h, the germinating seedlings were transferred to dry filter paper and desiccated in room conditions for 14 or 30 days. Then, the seedlings were rewetted, each with its original solution. Seedlings that continued to grow after rewetting were counted as seedlings that had survived desiccation. Three of the four species were found to have seedlings with high percentages of desiccation tolerance, even after 30 days of desiccation, with the exception of Kochia prostrata which had low percentages of survival after desiccation. The ability of seedlings to germinate, survive and renew their elongation in up to 2% NaCl even after long periods of desiccation is not common and is an important survival strategy for species which inhabit saline deserts with unpredictable amounts and distribution of rain. Poster 27

EVIDENCE OF SIGNAL EXCHANGE BETWEEN THE HOST PLANT (HELIANTHEMUM SESSILIFORUM) AND THE SYMBIOTIC FUNGUS TERFEZIA

BOUDIERI

Turgeman T.1, Kagan-Zur V.2, Bejerano N.2, Kapulnik Y.3, Ben-Asher J.1, and Sitrit Y.1 1. The Jacob Blaustein institutes for desret research, Ben Gurion University of the Negev 2. Life Sciences, Ben Gurion University of the Negev 3. Institute of Plant Sciences, ARO, the Volcani Center, Bet Dagan Mycorrhiza enables plant roots to better absorb nutrients and water from the soil by the external fungal hyphae. In return the fungus acquires from the plant (host) photoassymilates. This type of mutualistic relationship exists in the majority of plant ecosystems and is account for plant-growth and nutrients cycling. Some mycorrhitic fungi produce edible fruit bodies, highly valued due to their organoleptic qualities (e.g truffles). In the Negev desert, the fungus Terfezia boudieri forms mycorrhiza with Helianthemum sessiliforum and produces edible sporocarps during the spring season. In spite of its essential ecological role and economical importance, little is known about the pre-infection stages of mycorrhizal fungus, when signals are exchanged between the host and the fungus. H. sessiliforum plants were co-cultured with T. boudieri isolates. Attraction of the fungus to host was observed under three levels of sucrose (0.25%, 0.5%, and 1%). Interestingly, on 1% sucrose plate, a root repealing phenomenon was observed. Infected plants exhibited short, thick and branched roots. To characterize the saprophytic stage in the fungus life cycle, its ability to grow on different carbon sources was determined. The co-culture model is currently employed to study the signals exchanged between the plant and fungus during the pre-infection stages.

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Poster 28

EXPRESSION OF A BACTERIAL BIFUNCTIONAL FEEDBACK INSENSITIVE CHORISMATE MUTASE/PREPHENATE DEHYDRATASE GENE REVEALS

NOVEL INSIGHTS INTO THE REGULATION OF AROMATIC AMINO ACIDS METABOLISM IN ARABIDOPSIS

VERED TZIN, SERGEY MALITSKY, ASAPH AHARONI AND GAD GALILI Department of Plant Sciences, The Weizmann Institute of Science, Rehovot 76100 Israel Phenylalanine (Phe) is a highly important amino acid in plants being a precursor for metabolites that play multiple roles in growth and interaction with the environment. Plants can synthesize Phe via Arogenate, but it is still unknown whether an alternative route, via Phenylpyruvate, exists, as in many microorganisms. We have expressed in Arabidopsis thaliana plants, a bacterial bifunctional PheA (Chorismate Mutase /Prephenate Dehydretase) gene that converts Chorismate via Prephenate into Phenylpyruvate. Plants expressing PheA gene, displayed a significant overproduction of Phe as well as a number of Phe-derived metabolites. This implied that plants can convert Phenylpyruvate into Phe and also that the level of Phe influences the pattern of its catabolism into various classes of secondary metabolites. Notably, the levels of Homogentisate and Tocochromanol that are derived from Tyrosine catabolism were enhanced in these plants. In addition, PheA expressing plants caused sensitivity to Tryptophan biosynthesis inhibitor. Furthermore, the levels of several Tryptophan catabolic products, including derivatives of the hormone IAA, were reduced in plants expressing the PheA gene. Thus, this study engenders novel insights into the regulation of plant Phe metabolism, its cross-regulation with the network of aromatic amino acids and the regulatory interface between primary and secondary metabolism. Poster 29

A REGULATORY ROLE FOR PROTEIN DISULFIDE ISOMERASE IN ARABIDOPSIS THALIANA CHLOROPLASTS

Gal Wittenberg Alex Levitan, Inbal Dangoor, Hadas Peled-Zehavi, Avihai Danon Department of Plant Science, Weizmann Institute of Science, Rehovot, Israel In plants, members of the thioredoxin superfamily have been implicated as regulators of light-controlled redox signaling. Protein disulfide isomerase (PDI) is an oxidative member of the thioredoxin superfamily. The chloroplast PDI of the unicellular alga Chlamydomonas reinhardtii was shown to regulate translation of psbA mRNA, encoding the PS II core protein D1, in response to light intensity. To study the role of chloroplast PDIs in higher plants, we first identified a PDI (AtPDI6) localized to Arabidopsis thaliana chloroplasts. AtPDI6 was active in catalyzing oxidative refolding of proteins in vitro, suggesting an oxidative role in vivo. Interestingly, AtPDI6 deficient plants (AtPDI6) displayed resistance to photoinhibition in comparison with w.t. plants. Although the steady state D1 levels appeared to be similar in AtPDI6 and w.t. plants under high light conditions, both D1 translation and degradation rates were found to be higher in AtPDI6 compared to w.t. plants. In addition, AtPDI6 mRNA levels increased during exposure to high light. These findings suggest that AtPDI6 is a high light response gene, down regulating D1 turnover when plants are exposed

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to high light. Further studies will focus on uncovering the molecular mechanism of D1 regulation by AtPDI6. Poster 30

THE INVOLVEMENT OF A TOMATO MAPKKK IN PLANT IMMUNITY

Shiri Melech-Bonfil and Guido Sessa

Department of Plant Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel

Resistant plants have evolved the capability to protect themselves from disease-causing organisms by activating a wide array of defense responses. In our lab, we investigate resistance of tomato (Solanum lycopersicum) to two different Gram-negative bacteria: Xanthomonas campestris pv. vesicatoria (Xcv) and Pseudomonas syringe pv. tomato (Pst), which are the causal agents of spot and speck diseases, respectively. These pathogens colonize the aerial parts of the plant and cause economically important loss to tomato yield worldwide. Control of speck and spot diseases by cultural practices or chemicals is not effective and genetic sources of resistance are only limited to certain Pst and Xcv strains. To isolate genes involved in these resistance responses, we used a functional screen based on virus-induced gene silencing (VIGS). Silencing of a MAP kinase kinase kinase, SlMAPKKK, compromised resistance to both bacterial pathogens and its overexpression elicited a pathogen-independent cell death. In addition, by silencing SlMAPKKK in N. benthamiana plants, we found that this gene is a key regulator of cell death mediated by the specific Pto and AvrPto interaction. Moreover, we found that this gene is specifically involved in the development of HR activated by pairs of resistance genes and avirulence genes form tomato and the leaf mold fungus Cladosporium fulvum, respectively. We also tested the hypothesis that SlMAPKKK might play a role in disease susceptibility. Using VIGS, we showed that SlMAPKKK kinase did not affect the bacterial growth in susceptible plants and it is not essential for disease susceptibility. These results reveal a role for SlMAPKKK gene in plant disease resistance and in the elicitation of cell death. Poster 31

SEASONAL CHANGES IN FUNCTIONAL ANATOMY INFLUENCE WATER BALANCE OF CUT BRANCHES OF DODONAEA 'DANA'

Ilana Shtein1,2, Shimon Meir1, Joseph Riov2 and Sonia Philosoph-Hadas1

1ARO, The Volcani Center, Dept. of Postharvest Science of Fresh Produce, Bet Dagan,

Israel; 2The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, The Robert H. Smith Institute of Plant Sciences and

Genetics in Agriculture, Rehovot, Israel Cut branches of Dodonaea 'Dana', a local hybrid, have a high export potential as decorative foliage, but have limited vase life due to leaf wilting and abscission. The wilting problem results primarily from improper water conductance. Our results demonstrate that Dodonaea vase life length changes during the year- when in winter the cut branches wilt after only one

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week and in summer survive 2-3 weeks. Leaf trichome density was correlated to seasonal temperatures - possibly, a mechanism for preventing water loss. Seasonal changes in leaf trichome and stomata density were correlated to branch weight during the vase life. Detached leaves' vase life during the year was longer than whole branches', indicating a higher resistance to water transport in the stem- however, no occlusions or tyloses were found in the stem vessels. Dodonaea branches are sensitive to air embolism, indicated by faster wilting of branches recut in air. Maximum vessel length was higher in cold season, which can suggest different resistance to air embolism. In addition, vessel diameter in the course of the year was negatively related to branch weight during the vase life- also a likely adaptation for preventing air emboli formation. Vessel number was higher during the warm season. In conclusion, Dodonaea 'Dana' branches show seasonal anatomical changes which lead to differential resistance to embolism and water stress. Poster 32

CHARACTERIZATION OF KARYOPHERIN α 1 GENE EXPRESSION IN IAA OVER PRODUCING PLANTS

K. Rand1,2 , I. Kobrinsky 2, D. Dabush2, Y. Levy2, R. Aloni1 and Y. Gafni2 1 Department of Plant Sciences, Tel Aviv University, Israel. 2 Department of Plant Genetics, Volcani Center, Bet Dagan, Israel The Tomato yellow leaf curl disease decreases the yield of tomato production in many tropical and subtropical countries all over the world, causing great economic damage to growers. The disease caused by the Tomato yellow leaf curl virus. (TYLCV ) is transmitted by the whitefly Bemisia tabaci Genadius. TYLCV is an ssDNA virus, therefore it must enter the host cell's nucleus for the replication and transcription of its genome. Macromolecules may transfer between the cytoplasm and the nucleus, only through specific gates - The Nuclear Pore Complexes (NPCs). Transfer through the NPC is contingent upon interaction with the protein which needs to be transferred (cargo) to a receptor named Karyopherin. Recent evidence suggests that specific interaction of the virus Coat Protein (CP) with the tomato's Karyopherin LeKAPα1