The NADPH oxidase OsRbohD and OsRbohH negatively regulate saline-alkaline tolerance in rice

Excessive alkaline salt in the soil caused by saline-alkaline stress has significant negative impacts on the growth of rice (Oryza sativa L.). Here, we find OsRbohD and OsRbohH, the rice NADPH oxidase, negatively regulate saline-alkaline tolerance in rice. osrbohd or osrbohh mutants display a greater saline-alkaline tolerance than other osrhohs mutants and WT. Under NaHCO3 treatment, the accumulation of Na+ and loss of K+ in the shoots and roots were decreased, which means OsRbohD or OsRbohH confer the Na+ and K+ variations in the shoots and roots under saline-alkaline stress. Meanwhile, osrbohd or osrbohh mutants have faster K+ influx and H+ efflux in the roots, thus enhancing Na+/K+ and Na+/H+ homeostasis. Furthermore, lacking of OsRbohD or OsRbohH significantly decreases reactive oxygen species (ROS) levels in the tissue under saline-alkaline stress. In conclusion, our studies reveal a novel mechanism in which OsRbohD and OsRbohH negatively regulate saline-alkaline tolerance in rice by regulating Na+/K+ and Na+/H+ homeostasis and the production of reactive oxygen species (ROS) under saline-alkaline stress. That provides an important research direction for breeding saline-alkaline tolerant rice.