The PCY-SAG14 phytocyanin module regulated by PIFs and miR408 promotes dark-induced leaf senescence in Arabidopsis

Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research, identity of the senescence signal and the molecular mechanism that perceives and transduces the signal remain elusive. Using dark-induced leaf senescence as the experimental system, we found that senescence induces rapid reciprocal regulation of plastocyanin, a copper-binding electron carrier in the photosynthetic electron transport chain, and the PCY-SAG14 pair of phytocyanins located on the endomembrane. We also found that PCY-SAG14, which is modulated by PIF3/4/5 and miR408, is both necessary and sufficient to promote senescence. These findings indicate that intracellular copper homeostasis mediated by the PCY-SAG14 module plays an important regulatory role in dark-induced leaf senescence.