On January 22, 2025, researchers at CAS Center for Excellence in Molecular Plant Sciences led by Alberto Macho, published a study in the journal PLoS Pathogens, entitled “A bacterial type III effector hijacks plant ubiquitin proteases to evade degradation”, solving an unanswered question in plant-microbe interactions.

Most bacterial plant pathogens inject effector proteins inside host cells to suppress immune responses and manipulate other plant functions in order to cause disease. These effector proteins are exogenous and dangerous proteins for plant cells, and it is reasonable to think that they could be targeted by the plant protein degradation systems. However, they are able to perform their virulence functions, which suggests that they are relatively stable, even though the mechanisms leading to this stability remain poorly understood.

Ralstonia is the causal agent of bacterial wilt disease in important crops such as tomato, potato, banana, eggplant, and pepper, among others. In this study, the researchers found that RipE1, an effector protein secreted by Ralstonia, has the potential to be ubiquitinated and degraded in plant cells. However, RipE1 hijacks plant kinases and undergoes phosphorylation of specific residues inside plant cells, and this counteracts its ubiquitination and promotes its stability. Moreover, RipE1 associates with plant ubiquitin proteases, which contribute to RipE1 deubiquitination and stabilization.

This study therefore reveals that effector stability or degradation in plant cells constitute another molecular event subject to co-evolution between plants and pathogens, and that pathogen effectors hijack plant post-translational modification regulators in order to promote their own stability.

The co-first authors of this study are the former PhD student Wenjia Yu and the PhD student Meng Li, and the corresponding author is Alberto P. Macho.

Link to the article: 

https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1012882

Contact: Dr. Alberto P. Macho, Principal Investigator

Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences

Email: alberto.macho@cemps.ac.cn