The PDR-type ABC transporter OsPDR1 is involved in leaf senescence by influencing melatonin biosynthesis in rice

Leaf senescence is a complex developmental process that is regulated by multiple genetic and environmental factors. Understanding the mechanisms underlying the regulation of leaf senescence will provide valuable insights for manipulation of this trait in crops. Here, we report that the ATP-binding cassette (ABC) transporter OsPDR1 is involved in promoting leaf senescence in rice. Mutation and overexpression of OsPDR1 delayed and accelerated natural leaf senescence at the seedling and mature stages, respectively. The level of OsPDR1 transcript in leaves was significantly upregulated by dark treatment. Overexpression of OsPDR1 accelerated dark-induced leaf senescence by enhancing senescence-associated gene expression, whereas its mutation delayed dark-induced leaf senescence. OsPDR1 is coexpressed with the rice N-acetylserotonin methyltransferase gene, OsASMT1, encoding a key enzyme in melatonin biosynthesis. OsASMT1 expression levels and melatonin content were significantly decreased in OsPDR1-overexpressing lines but significantly increased in ospdr1 mutants compared to the wild type. Exogenous melatonin application markedly decreased the accumulation of reactive oxygen species (ROS) and delayed leaf senescence in PDR1.3-overexpressing plants. These results indicated that OsPDR1 plays an important role in the regulation of leaf senescence by influencing melatonin biosynthesis in rice.