[WRKY33A positively regulates disease resistance in soybean ()].

The WRKY transcription factor gene family is a plant-specific transcription factor that plays important roles defense responses. Studies in model plant demonstrated that WRKYs function downstream of mitogen activated-protein kinase (MAPK) signaling cascade and participate in defense responses through activating the expression of defense-related genes. However, the roles of WRKYs in defense responses have not been previously investigated in paleopolyploidy soybean. Bioinfomatic analysis revealed that there are three pair of genes in the soybean genome. The identity of first two pair of GmWRKY33 genes is greater than 84% (named as ). The identity of genes within the same pair is greater than 95%. A 300 bp fragment highly homologous to these four was chosen to clone into bean pod mosaic virus (BPMV)-based silencing vector (BPMV-VIGS) to achieve the goal of silencing four genes simultaneously. In this study, we simultaneously silenced four homologous genes of using a bean pod mottle virus (BPMV) vector carrying a single fragment of . Comparing the silenced plants with the vector control plants, no evident morphological phenotypes were observed. However, the silenced plants exhibited significantly reduced resistance to pv. (), pv. (), as well as to soybean mosaic virus (SMV). Furthermore, we demonstrated that silencing these genes significantly inhibited the activation of MPK3/MPK6 induced by infection. Collectively, our results suggest that WRKY33As are involved in soybean immunity through regulating the transcription of genes or activating the kinase activities of MPK3/6. Taken together, our results demonstrated that WRKY33As are positive regulators of soybean immune responses.