<i>OsAGO2</i> controls ROS production and the initiation of tapetal PCD by epigenetically regulating <i>OsHXK1</i> expression in rice anthers

Abstract

Proteins of the ARGONAUTE (AGO) family function in the epigenetic regulation of gene expression. Although the rice (<i>Oryza sativa</i>) genome encodes 19 predicted AGO proteins, few of their functions have thus far been characterized. Here, we show that the AGO protein OsAGO2 regulates anther development in rice. <i>OsAGO2</i> was highly expressed in anthers. Knockdown of <i>OsAGO2</i> led to the overaccumulation of reactive oxygen species (ROS) and abnormal anther development, causing premature initiation of tapetal programmed cell death (PCD) and pollen abortion. The expression level of <i>Hexokinase 1</i> (<i>OsHXK1</i>) increased significantly, and the methylation levels of its promoter decreased, in plants with knocked-down <i>OsAGO2</i> expression. Overexpression of <i>OsHXK1</i> also resulted in the overaccumulation of ROS, premature initiation of PCD, and pollen abortion. Moreover, knockdown of <i>OsHXK1</i> restored pollen fertility in <i>OsAGO2</i> knockdown plants. Chromatin immunoprecipitation assays demonstrated that OsAGO2 binds directly to the <i>OsHXK1</i> promoter region, suggesting that <i>OsHXK1</i> is a target gene of OsAGO2. These results indicate that OsHXK1 controls the appropriate production of ROS and the proper timing of tapetal PCD and is directly regulated by OsAGO2 through epigenetic regulation.