Identification of Peanut Transcription Factors and Their Multiple Roles in Drought Stress Responses.

MYB transcription factors (TFs) comprise a large gene family that plays an important role in plant growth, development, stress responses, and defense regulation. However, their functions in peanut remain to be further elucidated. Here, we identified six genes (, , and ) in cultivated peanut. They are typical R2R3-MYB TFs and have many similarities but different expression patterns in response to drought stress, suggesting different functions under drought stress. Homologous genes with higher expression in each pair were selected for further study. All of them were nuclear proteins and had no self-transactivation activity. In addition, we compared the performances of different lines at germination, seedling, and adult stages under drought stress. After drought treatment, the overexpression of transgenic plants resulted in the longest root length at the seedling stage. Levels of proline, soluble sugar and chlorophyll, and expression levels of stress-related genes, including , , , and , were higher than those of the wild type (WT) at the adult stage. While the overexpression of significantly increased the drought sensitivity of plants at all stages, with differential ABA content, the expression levels of the ABA-related genes and were significantly upregulated and those of and were significantly downregulated compared with the WT. showed similar downregulated expression as under drought stress, but its overexpression in did not significantly affect the drought resistance of transgenic plants. Based on the results, we propose that plays a role as a positive factor in drought tolerance by increasing the transcription abundance of stress-related genes and the accumulation of osmolytes, while negatively regulates drought tolerance through its involvement in ABA-dependent stress response pathways.