Poster: Education

Abs # 30: Regulation of dark-induced leaf senescence in P_SAG12-IPT transgenic and wild type tobacco by cytokinins and ethylene

Presenter:	Singh, Santokh , santokh@interchange.ubc.ca
Authors	Singh, Santokh  (A)   Penugonde, Rashmi  (A)   Li, Michelle  (A)   Mehroke, Jarnail  (A)
Affiliations:	(A): Department of Botany, University of British Columbia

Effect of cytokinins and ethylene on dark-induced leaf senescence in wild-type and transgenic tobacco plants (Nicotiana tabacum cv. Wisconsin) expressing ISOPENTENTL TRANSFERASE (IPT) (gene encoding isopentenyl transferase) with the SAG12 promoter (P_SAG12 - a highly specific senescence associated gene) was investigated. Tobacco plants containing P_SAG12-IPT retarded senescence in intact leaves as well as in leaf disks in the dark. Application of cytokinins, zeatin (Z), dihydrozeatin (DZ) or benzylamino purine (BAP) at 10^-4 M retarded senescence of leaf disks of wild-type tobacco but had little effect on leaf senescence of P_SAG12-IPT transgenic plants. On the other hand, 2-chloroethyl phosphonic acid (CEPA - an ethylene releasing compound) (10^-4 M) accelerated senescence of leaf disks of wild-type tobacco but had little effect on leaf senescence of P_SAG12-IPT transgenic plants. Cytokinin levels in wild-type and P_SAG12-IPT transgenic plants were analyzed by enzyme-linked immunosorbent assay. Leaves of P_SAG12-IPT transgenic plants had higher levels of Z, DZ and their ribosides in comparison to WT. The possible involvement of cytokinins and ethylene in leaf senescence in wild-type and P_SAG12-IPT transgenic plants will be discussed.