Screening for mutants with delayed leaf senescence in Arabidopsis

Senescence is the last stage of development in plants. During foliar senescence, theleaves experience changes in metabolism, cell structures and gene expression. In thisprocess the limiting nutrients of leaves are relocated from senescing organs to thedeveloping leaves, fruits and buds. The genetic screening to identify senescence mutantsis of utmost importance both for scientific research and for future biotechnology becausethe stay green mutants could increase crop yields.In our experimental setup, the senescence was induced by darkening the individual leavesof Arabidopsis thaliana plants with “mittens” for six days. We have screened 1064Arabidopsis plants for the mutants with delayed senescence phenotypes (stay-green,light-green and slightly light green plants) by measuring chlorophyll content, proteincontent and change in protein levels of the rubisco LSU, COXII, GS1 and GS2 duringdark induced senescence. After senescence induction, the wild type plants had showntypical yellowing and drying of leaves coupled with chlorophyll and protein degradation,while the foliar senescence progresses more slowly in selected stay green mutants. Theselected stay green mutants (19/29, 19/1043 and 19/531) delayed the degradation ofchlorophyll and protein contents even after 6 days of dark treatment. Furthermore, theretention of chloroplast and mitochondrial protein (rubisco LSU and GS2, and COXIIrespectively) and their higher chlorophyll contents may suggest that 19/29, 19/531and19/1043 plants may maintain their photosynthetic and respiratory activities. Thesemutants delay the functional leaf senescence and could be candidates for functional staygreen mutants for upcoming experiments