StCPP3 interacts with type III secretion protein HrpB7 and negatively regulates plant resistance against Ralstonia solanacearum.

Cysteine-rich polycomb-like proteins (CPP) are crucial in regulating plant stress responses while the underlying functions of CPP involving plant- Ralstonia solanacaearum interaction remain unknown. Here, we showed the expression patterns of a potato CPP gene (StCPP3) under phytohormone treatments, biotic and abiotic stressed and its role in resistance against of R. solanacaearum infection by loss- and gain-of-function approaches. StCPP3 expression were up-regulated with methyl jasmonate (MeJA) and abscisic acid (ABA) while down-regulated under salicylic acid (SA), brassinosteroids (BR), high salt or low temperature treatment. Silencing the homolog gene (NbCPP3) in Nicotiana benthamiana enhanced resistance to R. solanacaearum. Over-expressing StCPP3 in Arabidopsis increased susceptibility and decreased activity of some defense-related enzymes, suggesting its role in suppressing hypersensitive cell death and reducing PR1 gene expression. In addition, we found that StCPP3 could interact with Type III secretion protein HrpB7 from R. solanacaearum. These results provide new insight into the mechanism of CPP's involvement in plant-pathogen interactions.