GmSGT1 is differently required for soybean Rps genes-mediated and basal resistance to Phytophthora sojae.

Using RNAi approach, we demonstrate that GmSGT1 is an essential component in soybean against Phytophthora sojae, but not required for Rps 2 or Rps 3a-mediated resistance. Utilization of disease resistance in soybean is a major approach to combat root and stem rot disease, which is caused by Phytophthora sojae and poses a growing threat to soybean safety production. The SGT1 protein is essential for disease resistance in many plant species. Here, we analyzed and characterized functions of GmSGT1 gene family in R protein-mediated resistance and basal defense in this important crop. Five candidate genes of GmSGT1 were identified and they were grouped into three clades. Transcriptional levels of all the tested genes were highly induced upon P. sojae infection in four soybean cultivars that confer different resistant levels. Using a gene silencing system in soybean cotyledons, we demonstrated that silencing GmSGT1 genes comprised race-specific resistance in soybean lines carrying genes at the following loci for race-specific resistance to P. sojae: Rps1a, Rps1c, Rps1d, Rps1k, and Rps8. In contrast, the resistance mediated by Rps2 or Rps3a was not affected. Silencing GmSGT1 genes in cotyledons also reduced resistance to this pathogen in a moderately partial resistant cultivar. We further showed that transient overexpression of GmSGT1-1 in Nicotiana benthamiana could enhance the resistance to P. capsici. These results suggest that GmSGT1 is an essential component for soybean in resisting the pathogen and pathways of Rps-mediated disease resistance are diverse in soybean.