BnaMYB73, a Brassica napus L. R2R3-MYB Transcription Factor, Enhances Plant Salt and Osmotic Stress Tolerance

MYB transcription factors (TFs) are crucial for plant growth, development, and response to abiotic stress. However, their exact functions in abiotic stress responses in rapeseed remain largely unexplored. In this study, we identified and characterized <i>BnaMYB73</i>, a member of the R2R3-MYB subfamily, and investigated its role in abiotic stress tolerance. The transcription level of <i>BnaMYB73</i> was significantly upregulated in response to salt and osmotic stress. Transgenic <i>Arabidopsis thaliana</i> lines expressing <i>BnaMYB73</i> displayed significantly enhanced tolerance to salt and osmotic stress, while showing no phenotypic differences in growth compared with wild-type (WT) plants under normal conditions. Physiological analyses revealed that the <i>BnaMYB73</i>-expressing plants accumulated higher proline levels, exhibited elevated superoxide dismutase (SOD) and peroxidase (POD) activities, and reduced malondialdehyde (MDA) content under stress conditions. Moreover, the <i>BnaMYB73</i>-expressing plants significantly upregulated key stress-responsive genes, including <i>AtRD29B</i>, <i>AtDREB2A</i>, <i>AtRAB18</i>, <i>AtP5CS1</i>, <i>AtSOS1</i> and <i>AtCAT1</i>. Collectively, these findings establish BnaMYB73 functions as a stress-responsive transcription factor that enhances abiotic stress tolerance and provide a promising target for breeding stress-resilient rapeseed cultivars.