Plants Trick Bacteria With A Decoy

Tweaking a decoy signaling molecule—PBL2—helps plants detect and respond to an infection by pathogens.

AsianScientist (Sep. 17, 2015) – A study published in Cell Host Microbe has shown that plants can fight back against bacterial infections using decoy proteins such as PBL2.

Animals and plants are equipped with immune receptors to recognize pathogens and trigger immune responses, a process crucial for health in humans and disease resistance in crop plants. One class of such immune receptors is called NLRs that are shared between animals and plants.

Pathogenic bacteria often inject a suite of proteins into their animal or plant host cells to assist infection. Sometimes, these proteins can be recognized by NLRs and trigger immune responses in the host. How NLRs recognize pathogen effectors is not well-understood.

Two research groups led by Dr. Zhou Jianmin at the Institute of Genetics and Developmental Biology of Chinese Academy of Sciences (IGDB) and Dr. Laurent Noël at INRA, Laboratoire des Interactions Plantes Microorganismes teamed up to show how a plant NLR uses a unique mechanism to turn a virulent bacterium into an avirulent one.

They have previously shown that Xanthomonas campestris, a causal agent of black rot on cabbage, inject a protein called AvrAC to assist infection. AvrAC does so by adding a nucleotide to a plant protein called BIK1, thereby inhibiting a host process mediated by BIK1.

In this study, the researchers showed that plants possess a decoy protein called PBL2 that is similar to BIK1 and can be similarly modified by AvrAC. Instead of making plants more susceptible to the bacterium, the modification on PBL2 allowed plants to detect the pathogen and trigger immune responses.

The team further showed that the modified PBL2 was specifically recruited to a immune receptor complex composed of an NLR protein called ZAR1 and a pseudokinase called RKS1. This recruitment then activated disease resistance in plants.

The findings uncovers a novel biochemical mechanism by which plants recognize pathogens and brings new insight into host-pathogen co-evolution.

The article can be found at: Wang et al. (2015) The Decoy Substrate of a Pathogen Effector and a Pseudokinase Specify Pathogen-Induced Modified-Self Recognition and Immunity in Plants.


Source: Chinese Academy of Sciences.
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