Comparative transcriptome analysis of ethylene- and cytokinin-regulated leaf senescence

Abstract

Leaf senescence involves degenerative but active biological processes that require balanced regulation of pro- and anti-senescing activities. Ethylene and cytokinin are major antagonistic regulatory hormones that control the timing and progression rate of leaf senescence. To identify the roles of these hormones in the regulation of leaf senescence in Arabidopsis, global gene expression profiles in detached leaves of wild type, an ethylene-insensitive mutant (ein2/ore3), and a constitutive cytokinin response mutant (ahk3/ore12) were investigated during dark-induced leaf senescence. Comparative transcriptome analyses revealed that genes involved in oxidative or salt stress response were preferentially altered in ein2/ore3 mutant, whereas genes involved in ribosome biogenesis were affected in ahk3/ore12 mutant during dark-induced leaf senescence. Similar results were also obtained in developmental senescence. Extensive molecular and physiological analyses in ein2/ore3 and ahk3/ore12 during dark-induced leaf senescence, together with responses treated with ethylene inhibitor and cytokinin, were concluded that ethylene acts as a senescence-promoting factor via the transcriptional regulation of stress-related responses, whereas cytokinin acts as an anti-senescing agent by maintaining cellular activities and preserving the translational machinery. These findings provide new insights into how plants utilize two antagonistic hormones, ethylene and cytokinin, to regulate the molecular programming of leaf senescence.