The role of pyrophosphatase in mitochondrial function and drought stress response in rice

Soluble pyrophosphatase (sPPase) plays a crucial role in plant stress resistance, but its role in mitochondrial function remains poorly understood. In this study, eight OsPPase gene family members were identified in rice. Among them, OsPPa3 (LOC_Os04g59040) exhibited dual localization to mitochondria and nucleus. OsPPa3 knockout impaired mitochondrial function, manifested by reduced mitochondrial membrane potential, ATP levels, and mitochondrial complex V activity, alongside an increased ROS (reactive oxygen species) accumulation. Under drought stress, osppa3 mutants displayed heightened sensitivity, including accelerated leaf wilting, water loss, reduced proline, chlorophyll levels, elevated MDA (malondialdehyde) content, and impaired SOD (superoxide dismutase) and CAT (catalase) activities. Transcriptome analysis revealed drought-induced downregulation of light-harvesting chlorophyll genes (OsLhca/OsLhcb) in osppa3 mutants, associated with decreased expression of the transcription factor OsWRKY50. Yeast one-hybrid (Y1H) and dual-luciferase assays confirmed OsWRKY50 directly bound to the promoter of OsLhcb5, a representative W-box-containing OsLhca/OsLhcb gene, and activated its expression. Furthermore, the downregulation of OsWRKY50 in the osppa3 mutants under drought stress also correlated with reduced expression of peroxidase (OsPrxs) genes, thereby contributing to impaired ROS scavenging capacity. These findings reveal a novel mechanism by which OsPPa3 enhances rice drought resistance via coordinated mitochondrial energy homeostasis, OsLhca/OsLhcb regulation, and OsWRKY50-dependent transcription, identifying a potential target for the development of stress-resistant crops.