Topic/s number/s: SFS-2B-2015: Sustainable crop production - Assessing soil- improving cropping systems Project Description: Alleviating drought stress: The role of Aquaporins in regulating hydraulic conductivity in response to drought and ABA in selected crop species. Partners search: UK experts in plant abiotic stress tolerance, especially drought stress, water and ion channels (aquaporins, transporters); experts in the evolution of plant drought stress tolerance. Organization: Hebrew University of Jerusalem, Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Rehovot Contact person: Dr. Menachem Moshelion (Senior Lecturer) – PI Professor (Emeritus) Arie Altman -

Alleviating drought stress tolerance: The role of Aquaporins in regulating the bundle sheath and endodermis hydraulic conductivity in response to drought and ABA The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, and Food and Environment, Rehovot, The Hebrew University of Jerusalem Dr. Menachem Moshelion (Senior Lecturer) – PI and Professor (Emeritus) Arie Altman Abiotic stress tolerance, especially drought and salinity, is nowadays the single most important trait of relevance to sustainable crop production. It is a complex trait to breed for, however solvable in part

-, - The complexity of plant responses to abiotic stress Acquired Plant Stress Tolerance Plant Breeding and Molecular markers (e.g.QTL’s) Genetic transfor- mation Stress-associated metabolites Carbon, Amino acid, Fatty acids metabolism Other stress- response mechanisms (eg.Apoptosis) Osmolytes, Osmoprotectants Hormones, Polyamines, ROS scavengers Stress-associated genes and proteins Signaling pathways, Transcription Factors Ion and water transporters, aquaporins HSP’s/ chaperones and LEA proteins ROS scavenging and detoxification Vinocur and Altman (2005) Current Opinion in Biotechnology

Unique anatomic structure implies the role of two tissues controlling plant water conductance (Taiz and Zeiger, 2002) The root endodermis The shoot bundle sheath (BS) BS

The main mediators: Aquaporins – water channels Trans-membrane water channels proteins which facilitate the transport of water and/or small neutral solutes (urea, glycerol, boric acid). In plants, AQPs are classified into 4 subfamilies (PIPs, TIPs, NIPs, SIPs). Their function is regulated by several processes, such as gene expression, protein activity and protein trafficking. Aquaporins involvement in leaf hydraulic conductance regulation It is most likely that AQPs evolution across plant species is of great relevance their water transport efficiency (Maurel C. 2007)

The radial hydraulic conductivity of the leaf - K leaf K leaf determined as the ratio of water flow rate through the leaf to the flow driving force. K leaf decreases dramatically in response to many environmental and abiotic stresses. (AQPs involvement). Logically, the anatomical location of the BS layer should expose it to long-distance signals coming from the roots. In dehydrated plants, the concentration of the stress phytohormone abscisic acid (ABA) progressively increased in the xylem sap. BS

The bundle sheath cells (BSCs) and endodermis play a key role in controlling leaf and root hydraulic conductivity (K) in response to ABA stress signal, going through the vascular system. Hypothesis Mesophyll Vein ending tracheid Bundle sheath (Taiz and Zeiger, 2002) The root endodermis

Objectives To understand AQPs evolution across relevant crop plants by: Characterizing the transcript levels of all (35) aquaporins expresed in the BSc and endodermis cells under well- irigated and drought conditions. Characterize their expresssion profile in response to ABA added directly to the protoplasts. Examine the BSc and endodermis role in the regulation of K in response to drought and ABA. Identify, by silencing, those BSCs AQPs which mediate K leaf decrease in response to xylem application of ABA All experiments are assessed by both genotyping and phenomics, thus bridging the genotype to phenotype gap

Sade et. al., (2009) New Phytologist. 181: 651–661. Selected Publications (M. Moshelion et al.)

Shatil-Cohen et. al,.(2011) The Plant Journal 67: 72–80. And more…