Professor Institute of Molecular Biology, Academia Sinica Taipei, Taipei, Taiwan (Republic of China)
Mitochondria, as the powerhouse in eukaryotic cells, are affected by various biotic and abiotic stresses. Our studies indicate that maintaining functional and flexible mitochondrial metabolisms via retrograde regulation of nuclear genes facilitates plant adaption to stressful environments. We identified an oxidase gene (OX) that is functioning in mitochondria for metabolic and signaling homeostasis in response to hypoxia in rice. We observed that H2O2 activates the expression of OX and genes encoding enzymes involved in H2O2 homeostasis in mitochondria, as well as genes that regulate sugar production, glycolysis, and ethylene biosynthesis essential for rice seedling development under hypoxia/submergence. We also identified several protein kinases and transcription factors that could be involved in hypoxia signaling. We demonstrated that OX is necessary and sufficient for germination and seedling development, as well as H2O2 accumulation, in rice under both aerobic and anaerobic conditions. Moreover, ectopic expression of OX enhances lateral root emergence that enhance root system under submergence, as well as photosynthesis rates and grain yield in the field under regular and limited irrigation conditions. Our discoveries reveal new insights into a unique regulatory mechanism for regulating seedling development in rice under submergence, and highlight genes as potential targets for crop improvement.