Proteomic analysis of potato responding to the invasion of Ralstonia solanacearum UW551 and its type III secretion system mutant

The infection of potato with Ralstonia solanacearum (R. solanacearum) UW551 gives rise to bacterial wilt disease via colonization of roots. The Type III Secretion System (T3SS) is a determinant factor for the pathogenicity of R. solanacearum. To fully understand perturbations in potato by R. solanacearum Type III Effectors(T3Es), we use proteomics to measure differences in potato root protein abundance after inoculation with R. solanacearum UW551 and T3SS mutant (UW551△HrcV). We identified 21 differentially accumulated proteins (DAPs). Compared to inoculation with UW551△HrcV, ten proteins showed significantly lower abundance in potato roots after inoculation with UW551, indicating those proteins were significantly down-regulated by T3Es during the invasion. To identify their functions in immunity, we silenced those genes in Nicotiana benthamiana and tested the resistance of the silenced plants to the pathogen. Results showed that miraculin, HBP2, TOM20 contribute to immunity to R. solanacearum. In contrast, PP1 contribute to susceptibility. Notably, none of four downregulated proteins (HBP2, PP1, HSP22, TOM20) were downregulated at the transcriptional level, suggesting that they were significantly down-regulated at the post-transcriptional level. We further co-expressed those four proteins with thirty-three core T3Es. To our surprise, multiple effectors were able to significantly decrease the sudied protein abundances. In conclusion, our data showed T3Es of R. solanacearum could subvert potato root immune-related proteins in a redundant manner.