ThDIV2, an R-R-type MYB transcription factor of Tamarix hispida, negatively regulates cadmium stress by modulating ROS homeostasis

Cadmium (Cd) is a nonessential and toxic metal that is rapidly taken up by roots and accumulates in various plant tissues, limiting crop growth and productivity. ROS generation and signal transduction play an important role in the detoxification and tolerance of heavy metals (e.g., Cd stress). Nonetheless, the mechanism underlying the regulation of ROS in T. hispida under Cd stress remains largely unknown. Here, we have demonstrated a previously unknown role of the R2R3-type MYB transcription factor ThDIV2 in regulating Cd tolerance by downregulating the expression of ThAO1 and ThAO2. To investigate the role of R2R3-type MYB transcription factor ThDIV2 in regulating Cd tolerance, we monitored the expression level of ThDIV2 in response to Cd stress using qRTPCR. Additionally, we conducted a Qu-2 cell conversion experiment to determine the subcellular localization of ThDIV2. The results demonstrated that ThDIV2, which is localized in the nucleus, was significantly suppressed under Cd stress. To further investigate the function of ThDIV2 under Cd stress, we generated ThDIV2-overexpressing plants and empty an pBI121 vector (used as the control; VC) through transient transformation. Biochemical staining and physiological parameter analysis showed that overexpression of ThDIV2 resulted in higher ROS, H2O2 and proline contents, but lower T-AOC, SOD, POD, and CAT activity, and GSH content compared with VC under Cd treatment. Moreover, expression pattern analysis showed that ThDIV2 repressed the expression of ThAO1, ThAO2, ThAO3, ThSOD1, ThSOD2 and ThSOD3. Further Y1H and ChIP-PCR analyses indicated that ThDIV2 could directly bind to the Myb motif (CAACCA) of the ThAO1 and ThAO2 promoters. In summary, our results suggest that ThDIV2 regulates the expression of ThAO1 and ThAO2, leading to alterations in ROS content and increased sensitivity of T. hispida to Cd stress.