Phosphorylation-dependent association of a bacterial effector with plant 14-3-3 proteins enhances effector stability and bacterial virulence.

Gram-negative bacterial pathogens inject effector proteins inside plant cells using specialized secretion systems. These effectors manipulate plant cellular functions and suppress the plant immune system in order to promote bacterial proliferation. Although bacterial effectors are exogenous proteins that could be targeted by protein degradation systems within plant cells, they are able to perform their virulence functions. In this study, we found that RipBM, an effector protein secreted by the bacterial wilt pathogen Ralstonia solanacearum, undergoes phosphorylation at specific residues within plant cells, which enhances its stability. This phosphorylation promotes the interaction of RipBM with plant 14-3-3 proteins, which contributes to its deubiquitination and stabilization. Furthermore, we demonstrated that RipBM contributes to Ralstonia virulence in tomato plants and that its phosphorylated residues, required for 14-3-3 interaction, are essential for this virulence function. These findings suggest that RipBM hijacks plant 14-3-3 proteins to promote its own stability and virulence activity. This highlights effector stability and degradation in plant cells as a critical molecular battleground in the coevolutionary arms race between plants and pathogens.