Ralstonia solanacearum type III effector RipAS associates with potato type one protein phosphatase StTOPP6 to promote bacterial wilt

Abstract

The bacterial pathogen Ralstonia solanacearum (R. solanacearum) delivered type III secretion effectors to inhibit the immune system and cause bacterial wilt on potato. Protein phosphatases are key regulators in plant immunity, which pathogens can manipulate to alter host processes. Here, we show that a type III effector RipAS can reduce the nucleolar accumulation of a type one protein phosphatase (PP1) StTOPP6 to promote bacterial wilt. StTOPP6 was used as bait in the Yeast two-Hybrid (Y2H) assay and acquired an effector RipAS that interacts with it. RipAS was characterized as a virulence effector to contribute to R. solanacearum infection, and stable expression of RipAS in potato impaired plant resistance against R. solanacearum. Overexpression of StTOPP6 showed enhanced disease symptoms when inoculated with wild strain UW551 but not the ripAS deletion mutant, indicating that the expression of StTOPP6 facilitates the virulence of RipAS. RipAS reduced the nucleolar accumulation of StTOPP6, which occurred during R. solanacearum infection. Moreover, the association also widely existed between other PP1s and RipAS. We argue that RipAS is a virulence effector associated with PP1s to promote bacterial wilt.

Acknowledgements

We thank Dr Caitilyn Allen and the late Dr Philippe Prior for providing us with R. solanacearum strains. We also thank all members of the potato group in Huazhong Agricultural University for supporting this project. This work was funded by the National Natural Science Foundation of China (32201789) and the China Agriculture Research System of MOF and MARA (CARS-09).

Author contributions

Conceived and designed the experiments: B.W., B.S., H.C. Performed the experiments: B.W., W.H., M.H., Y.W., Y.L., C.M. Analysed the data: B.W., W.H., L.Y., D.Z., D.C. Prepared the manuscript: B.W., M.H., B.S., H.C. Revised the manuscript: B.W., M.H., J.F., C.M., D.Z., D.C., N.T., B.S., H.C.

Data availability

All data supporting the findings of this research are available within the paper and within its supplementary data published online.

Conflict of interest

The authors declare no competing interests.

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