WRKY12 represses GSH1 expression to negatively regulate cadmium tolerance in Arabidopsis

The WRKY transcription factor WRKY12 negatively regulates Cd tolerance in Arabidopsis via the glutathione-dependent phytochelatin synthesis pathway by directly targeting GSH1 and indirectly repressing phytochelatin synthesis-related gene expression. Cadmium (Cd) is a widespread pollutant toxic to plants. The glutathione (GSH)-dependent phytochelatin (PC) synthesis pathway plays key roles in Cd detoxification. However, its regulatory mechanism remains largely unknown. Here, we showed a previously unknown function of the WRKY transcription factor WRKY12 in the regulation of Cd tolerance by repressing the expression of PC synthesis-related genes. The expression of WRKY12 was inhibited by Cd stress. Enhanced Cd tolerance was observed in the WRKY12 loss-of-function mutants, whereas increased Cd sensitivity was found in the WRKY12-overexpressing plants. Overexpression and loss-of-function of WRKY12 were associated respectively with increased and decreased Cd accumulation by repressing or releasing the expression of the genes involved in the PC synthesis pathway. Transient expression assay showed that WRKY12 repressed the expression of GSH1, GSH2, PCS1, and PCS2. Further analysis indicated that WRKY12 could directly bind to the W-box of the promoter in GSH1 but not in GSH2, PCS1, and PCS2 in vivo. Together, our results suggest that WRKY12 directly targets GSH1 and indirectly represses PC synthesis-related gene expression to negatively regulate Cd accumulation and tolerance in Arabidopsis.