Potato transcription factor StMYB19 enhances drought tolerance by regulating ROS homeostasis and JA signalling...

The MYB transcription factor family plays important regulatory roles in plant growth and development. In this study, a investigation was conducted to elucidate R1-MYB transcription factor StMYB19 biological function in drought stress response. The tissue-specific expression analysis of the gene revealed that StMYB19 expression differed in various organs of potato variety 'Atlantic', with the highest expression in tubers. StMYB19 was genetically modified in 'Atlantic' to obtain overexpression and RNA interference (RNAi) lines. Phenotypic analysis of the StMYB19 overexpression and suppression lines before and after drought treatment revealed that the drought symptoms were relatively mild in the overexpression lines, whereas growth inhibition and leaf wilting were more pronounced in the suppressed expression lines. Further physiological analysis revealed that after drought treatment, the activities of SOD, CAT, and POD significantly increased in StMYB19-overexpressing lines, whereas the contents of H₂O₂ and MDA were relatively decreased, indicating that StMYB19 regulated the ROS dynamic balance. Meanwhile, the JA content increased significantly in the overexpression lines, suggesting that StMYB19 may enhance drought tolerance by regulating the JA pathway. StMYB19 binds to the MYB-binding motif 'TAACCA' in the promoter of the downstream gene StLOB4 and positively regulates its transcription. At the same time, it promotes the expression of StACX3 through protein interaction. Therefore, by activating these two key genes in the JA pathway, StMYB19 coordinates plant defense and growth under drought conditions. In summary, StMYB19 acts as an important transcription factor in the potato drought response by maintaining ROS homeostasis and activating the JA signaling pathway, thereby enhancing plant drought tolerance.