Rice ONAC016 promotes leaf senescence through abscisic acid signaling pathway involving OsNAP

Senescence-induced NAC (senNAC) TFs play a crucial role in senescence during the final stage of leaf development. In this study, we identified a rice senNAC, ONAC016, which functions as a positive regulator of leaf senescence. The expression of ONAC016 increased rapidly in rice leaves during the progression of dark-induced and natural senescence. The onac016-1 knockout mutant showed a delayed leaf yellowing phenotype, whereas the overexpression of ONAC016 accelerated leaf senescence. Notably, ONAC016 expression was upregulated by abscisic acid (ABA), and thus detached leaves of the onac016-1 mutant remained green much longer under ABA treatment. Quantitative RT-PCR analysis showed that ONAC016 upregulates the genes associated with chlorophyll degradation, senescence, and ABA signaling. Yeast one-hybrid and dual-luciferase assays revealed that ONAC016 binds directly to the promoter regions of OsNAP, a key gene involved in chlorophyll degradation and ABA-induced senescence. Taken together, these results suggest that ONAC016 plays an important role in promoting leaf senescence through the ABA signaling pathway involving OsNAP.