WRKY transcription factors down-regulate the expression of H2S-generating genes, LCD and DES in Arabidopsis thaliana

Hydrogen sulfide (H2S) is a gasotransmitter playing a vital role in response to biotic and abiotic stress for plants. In order to understand the transcriptional regulation of the genes that are responsible for endogenous H2S generation, the promoter sequences of l-cysteine desulfhydrase (LCD), D-cysteine desulfhydrase (DCD1, DCD2), desulfhydrase (DES) and nitrogen fixation synthetase (NFS1, NFS2) were analyzed. They are all found to contain a W-box, a characteristic core binding site for the plant WRKY transcription factors, which have important roles in the plant's responses to numerous stresses by modifying the expression patterns of their target genes. An electrophoretic mobility shift assay indicated that WRKY18 and WRKY60 interacted with the W-box in the promoters of the LCD, DCD1, DCD2, DES and NFS2 genes, whereas WRKY40 bound to the W-box of the NFS1 promoter. The expression levels of the LCD, DES and DCD1 genes were up-regulated, but the DCD2 was down-regulated in the plants with WRKY18, WRKY40 or WRKY60 mutations. The plants with double and triple mutations of WRKY18, WRKY40 and WRKY60 had a higher rate of H2S production during cadmium stress and were more resistant to the cadmium stress than the wild type or single mutants. These results suggest that WRKY transcription factors regulate the H2S signaling pathway in plants, allowing them to cope with cadmium stress.