The Role of Light and Circadian Clock in Regulation of Leaf Senescence

Leaf senescence is an integrated response of the cells to developmental age information and various environmental signals. Light, the primary source of energy for photosynthesis, greatly affects plant development including leaf senescence. The molecular mechanisms linking light signaling to leaf senescence have recently emerged, exploring the role of PHYTOCHROME-INTERACTING FACTORS (PIFs) as a central player leading to diverse senescence responses, senescence-promoting gene regulatory networks (GRNs) involving PIFs, and structural features of transcription modules in GRNs. Light sets and activates the circadian clock, which integrates environmental signals and coordinates developmental events throughout the life of the plant. Research advances have led to the discovery of the role of core clock components as senescence regulators and their underlying signaling pathways, as well as the age-dependent shortening of the circadian clock period. These discoveries highlight the close relationship between the circadian system and leaf senescence. Key issues remain to be elucidated, including the effect of light on leaf senescence in relation to the circadian clock, the identification of key molecules linking aging, light, and the circadian clock, and integration mechanisms of various senescence-affecting signals at the multi-regulation levels in dynamics point of view.