Rice ONAC005 inhibits precocious leaf senescence through a feed-forward regulatory loop involving OsNAP

Leaf senescence is a highly regulated biological process that marks the final stage of leaf development. The initiation and progression of this process are precisely controlled by complex regulatory networks involving numerous endogenous factors. Here, we demonstrate that ONAC005 functions as a negative regulator of the onset of leaf senescence. ONAC005 expression gradually declines during both natural and dark-induced senescence. onac005 mutants generated by T-DNA insertional and CRISPR/Cas9-mediated mutagenesis exhibited precocious leaf yellowing under natural and dark-induced conditions, while ONAC005-overexpressing plants retained leaf greenness much longer than the wild type. ONAC005 overexpression downregulates the expression of senescence-associated genes and chlorophyll degradation genes, whereas onac005 mutation upregulates their expression. ONAC005 reduces the response to abscisic acid, thereby delaying abscisic acid-induced senescence. Through in vivo and in vitro DNA-binding assays, we demonstrated that ONAC005 directly binds to the promoters of OsNAP and OsNAP-regulated chlorophyll degradation genes, leading to transcriptional repression. Furthermore, we identified specific DNA motifs that ONAC005 preferentially recognizes. Taken together, these results suggest that ONAC005 acts as a repressor of leaf senescence by repressing the OsNAP-mediated senescence signaling pathway.