Transcription Factor OsMYB2 Triggers Amino Acid Transporter OsANT1 expression to Regulate Rice Growth and Salt Tolerance

Amino acid transporters play important roles in plant growth and stress tolerance; however, whether the abscisic acid signaling pathway regulates their transcription in rice (Oryza sativa) under salt stress remains unclear. In this study, we report that the transcription factor OsMYB2 (MYB transcription factor 2) of the abscisic acid signaling pathway mediates the expression of the gene encoding the amino acid transporter OsANT1 (aromatic and neutral amino acid transporter 1), which positively regulates growth and salt tolerance in rice. OsANT1 was mainly expressed in the leaf blade and panicle under normal conditions and transports leucine, phenylalanine, tyrosine and proline, positively regulating tillering and yield in rice. Nevertheless, salt stress induced the accumulation of abscisic acid and strongly increased the expression level of OsANT1 in the root, resulting in enhanced salt tolerance of rice seedlings, as evidenced by higher proline concentration and antioxidant-like enzyme activities and lower malondialdehyde and hydrogen peroxide concentrations. Moreover, we showed that OsMYB2 interacts with the promoter of OsANT1 and promotes its expression. Overexpression of OsMYB2 also improved tillering, yield, and salt tolerance in rice. In conclusion, our results suggest that the transcription factor OsMYB2 triggers OsANT1 expression and regulates growth and salt tolerance in rice, providing insights into the role of the abscisic acid signaling pathway in the regulatory mechanism of amino acid transporters in response to salt stress.