Overexpression of Arabidopsis phosphoinositide-specific phospholipase C5 induces leaf senescence

Phosphoinositide-specific phospholipase C (PI-PLC) plays a central role in the phosphatidylinositol specific signal transduction pathway. Plant PI-PLCs have been demonstrated to be involved in various stimuli and physiological processes. Five Arabidopsis thaliana PI-PLC genes were overexpressed transiently in tobacco leaves, and one of them, AtPLC5, was stably expressed in transgenic Arabidopsis; a dexamethasone-inducible promoter was used. Expression of AtPLC5 in transiently transformed tobacco resulted in leaf senescence at 72 h after induction, while other AtPLC did not cause any visible changes. Stable overexpression of AtPLC5 in transgenic Arabidopsis resulted in clearly induced visible yellowing at 8 days after induction, meanwhile chlorophyll content was decreased, PI-PLC activity and electric conductivity were increased. qPCR results demonstrated that increased transcription of senescence-associated genes (SAG12, SAG13, SAG15, SAG18 and SAG29) were up regulated after AtPLC5 induction. When AtPLC5 fused with green fluorescent protein was transiently expressed in protoplasts prepared from Arabidopsis mesophyll cells, green fluorescence was clearly observed in the plasma membrane (PM). Moreover, western blot analysis indicated that AtPLC5 was found to be enriched in the PM fraction of transgenic Arabidopsis stably expressing AtPLC5. These results suggest that AtPLC5 is predominantly localized in the PM and may be a regulator of leaf senescence.