Plants initiate leaf senescence to reallocate energy and nutrients from the aging to developing tissues for optimizing growth fitness and reproduction at the end of growing season or under stress.  

Circadian clock is a ubiquitous molecular time-keeping mechanism in higher plants. It provides an adaptive advantage to higher plants by synchronizing internal growth behaviors with external daily changing environments. 

Jasmonate (JA), a lipid-derived phytohormone, is known as an important endogenous signal in inducing leaf senescence. However, whether and how circadian clock gates JA signaling to induce leaf senescence in plants remains elusive. 

Researchers from the Institute of Botany of the Chinese Academy of Sciences discovered that the Evening Complex (EC), a core component of circadian oscillator, negatively regulates leaf senescence in Arabidopsis thaliana. 

The transcriptomic profiling analysis reveals that EC is closely involved in JA signaling and response, consistent with accelerated leaf senescence unanimously displayed by EC mutants upon JA induction.  

They further found that EC directly binds the promoter of MYC2, which encodes a key activator of JA-induced leaf senescence, and represses its expression.  

Genetic analysis further demonstrated that the accelerated JA-induced leaf senescence in EC mutants is abrogated by myc2myc3myc4 triple mutation. Collectively, their results reveal how the core component of circadian clock gates JA signaling to regulate leaf senescence. 

This work entitled "Circadian Evening Complex represses Jasmonate-induced leaf senescence in Arabidopsis" has been published in Molecular Plant.  

The study was supported by the National Natural Sciences Foundation of China, Youth Innovation Promotion Association CAS, 'Youth 1000 plan' and the Chinese Academy of Sciences. 

A proposed model of the role of circadian Evening Complex in repressing jasmonate-induced leaf senescence. (Image by WANG Lei)