Overexpression of a tartary buckwheat R2R3-MYB transcription factor gene, FtMYB9, enhances tolerance to drought and salt stresses in transgenic Arabidopsis

Tartary buckwheat (Fagopyrum tataricum) is a traditional coarse cereal that exhibits strong plasticity in its adaptation to harsh and complicated environmental stresses. In an attempt to study the strong tolerance of tartary buckwheat, the FtMYB9 gene, which encodes an R2R3-MYB transcription factor protein, was functionally investigated. FtMYB9 expression was rapidly and strongly induced by ABA, cold, salt, and drought treatments in the seedling stage. A yeast one-hybrid system assay indicated that FtMYB9 is an activator of transcriptional activity, consistent with its roles as a transcription factor. Its overexpression in plants resulted in increased sensitivity to ABA at the germination and seedling stages compared to wild type. The overexpression of FtMYB9 increased tolerance to drought and salt stresses by the activation of some stress-related genes from both ABA-independent and ABA-dependent pathways in transgenic Arabidopsis. Furthermore, enhanced proline content and the activation of the P5CS1 gene implied that FtMYB9 may be involved in proline synthesis in plants. Collectively, these results suggest that FtMYB9 functions as a novel R2R3-MYB TF which plays positive roles in salt and drought tolerance by regulating different stress-responsive signaling pathways.