The OsAGO2–OsNAC300–OsNAP module regulates leaf senescence in rice.

ABSTRACT Leaves play a crucial role in the growth and development of rice (<italic>Oryza sativa</italic>) as sites for the production of photosynthesis. Early leaf senescence leads to substantial drops in rice yields. Whether and how DNA methylation regulates gene expression and affects leaf senescence remains elusive. Here, we demonstrate that mutations in rice <italic>ARGONAUTE 2</italic> (<italic>OsAGO2</italic>) lead to premature leaf senescence, with chloroplasts in <italic>Osago2</italic> having lower chlorophyll content and an abnormal thylakoid structure compared with those from wild‐type plants. We show that OsAGO2 associates with a 24‐nt microRNA and binds to the promoter region of <italic>OsNAC300</italic>, which causes DNA methylation and suppressed expression of <italic>OsNAC300</italic>. Overexpressing <italic>OsNAC300</italic> causes the similar premature leaf senescence as <italic>Osago2</italic> mutants and knocking out <italic>OsNAC300</italic> in the <italic>Osago2</italic> mutant background suppresses the early senescence of <italic>Osago2</italic> mutants. Based on yeast one‐hybrid, dual‐luciferase, and electrophoresis mobility shift assays, we propose that OsNAC300 directly regulates transcription of the key rice aging gene NAC‐like, activated by APETALA3/PISTILLATA (<italic>OsNAP</italic>) to control leaf senescence. Our results unravel a previously unknown epigenetic regulatory mechanism underlying leaf senescence in which OsAGO2–OsNAC300<italic>–OsNAP</italic> acts as a key regulatory module of leaf senescence to maintain leaf function. [ABSTRACT FROM AUTHOR]