Arabidopsis transcription factor WRKY45 confers cadmium tolerance via activating PCS1 and PCS2 expression

Cadmium (Cd) has long been recognized as toxic pollutant to crops worldwide. The biosynthesis of glutathione-dependent phytochelatin (PC) plays crucial roles in the detoxification of Cd in plants. However, its regulatory mechanism remains elusive. Here, we revealed that Arabidopsis transcription factor WRKY45 confers Cd tolerance via promoting the expression of PC synthesis-related genes PCS1 and PCS2, respectively. Firstly, we found that Cd stress induces the transcript levels of WRKY45 and its protein abundance. Accordingly, in contrast to wild type Col-0, the increased sensitivity to Cd is observed in wrky45 mutant, while overexpressing WRKY45 plants are more tolerant to Cd. Secondly, quantitative real-time PCR revealed that the expression of AtPCS1 and AtPCS2 is stimulated in overexpressing WRKY45 plants, but decreased in wrky45 mutant. Thirdly, WRKY45 promotes the expression of PCS1 and PCS2, electrophoresis mobility shift assay analysis uncovered that WRKY45 directly binds to the W-box cis-element of PCS2 promoter. Lastly, the overexpression of WRKY45 in Col-0 leads to more accumulation of PCs in Arabidopsis, and the overexpression of PCS1 or PCS2 in wrky45 mutant plants rescues the phenotypes induced by Cd stress. In conclusion, our results show that AtWRKY45 positively regulates Cd tolerance in Arabidopsis via activating PCS1 and PCS2 expression.