Facilitation of auxin biosynthesis and metabolism by salt stress in rice plants

Abstract

Abstract To investigate the effects of salt stress on the auxin in rice plants, we analyzed indole-3-acetic acid (IAA) and its metabolites in hydroponically grown rice plant seedlings (Oryza sativa cv. Nipponbare) and in the culture medium using LC-ESI/MS/MS. We found that the IAA level in the culture medium was increased about 20-fold due to salt stress treatment, while those in the shoots and roots were increased by less than twofold. The culture medium also contained high amounts of oxidized metabolites such as OxIAA, DiOxIAA, DiOxIAA-Glu, and DiOxIAA-Asp. The total amount of IAA and its metabolites in the shoots, roots, and culture medium was significantly increased with salt treatment. A salt stress-responsive increase in the IAA metabolites was observed in nine tested cultivars of rice. The results indicate that salt stress facilitates the metabolic turnover of IAA in rice plants and may open new insight into the role of auxin.