The UDP-glucuronic acid decarboxylase OsUXS3 regulates Na ion toxicity tolerance under salt stress by interacting with OsCATs in rice.

Overly Na ion in soil caused by salt stress has a significant negative impact on the growth and production of crops, especially rice (Oryza sativa L.). Therefore, it is vital for us to clarify how salt stress tolerance in rice is caused by Na ion toxicity. The UDP-glucuronic acid decarboxylase (UXS) is a critical enzyme in the biosynthesis of UDP-xylose, which is the key substrate of cytoderm synthesis in plants. In this study, we found that OsUXS3, a rice UXS, is a positive regulator to regulate Na ion toxicity under salt stress by interacting with OsCATs (Oryza sativa catalase; OsCAT). The expression of OsUXS3 was significantly up-regulated under NaCl and NaHCO treatments of rice seedlings. Meanwhile, by the genetic and biochemical evidence, knockout of OsUXS3 significantly increased reactive oxygen species (ROS) levels and decreased CAT activity under NaCl and NaHCO treatments in tissue. Furthermore, knockout of OsUXS3 caused excessive accumulation of Na  ion and rapid loss of K ion and disrupts Na/K homeostasis under NaCl and NaHCO treatments. Based on the results above, we can conclude that OsUXS3 might regulate CAT activity by interacting with OsCATs, which is not only characterized for the first time but also regulating Na/K homeostasis, positively regulating the Na ion toxicity tolerance under salt stress in rice.