|M.Sc Student||Carp Nov Marie Jeanne|
|Subject||Global Identification of Senescence-Associated Genes in|
|Department||Department of Biotechnology||Supervisor||Professor Emeritus Shimon Gepstein|
Senescence-associated genes (SAGs), previously isolated in our laboratory by the suppression subtraction hybridization (SSH) method have been used as a source for the study of large-scale expression profiles. Hybridization of the arrays which contained two-hundred and forty different senescence-associated cDNA clones were performed with mRNA isolated from leaves in different developmental stages; young, mature, early senescent, senescent and late senescent leaves. Results of the macro-arrays indicated the existence of different expression patterns of the senescence-related genes; part of them showed an early elevated expression whereas others were expressed late. Based on the deduced function, several categories of SAGs have been identified. SAGs encoding hydrolases involved in degradation such as cysteine proteases and proteasome related clones were identified. Genes related to recycling and detoxifications processes were isolated indicating the intensive remobilization of the degradation products. Another group of SAGs included genes related to plant defense responses, induced resistance and secondary metabolites synthesis. Some of the isolated SAG clones, which encode regulatory genes such as receptor kinases and zinc finger proteins may indicate their role in regulation of leaf senescence. Many of the isolated SAGs lack deduced known function yet. In summary, more than one hundred and twenty genes identified as SAGs in Arabidopsis complemente the limited information regarding possible physiological and biochemical pathways occurring during leaf senescence. These results aslo suggest the existence of novel cellular and biochemical events during leaf senescence.