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Updated: Jun 23, 2026

Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling
Published on: June 25, 2015
Host inhibition of a bacterial virulence effector triggers immunity to infection
Vardis Ntoukakis1, Tatiana S Mucyn, Selena Gimenez-Ibanez
1Sainsbury Laboratory, Colney, Norwich NR4 7UH, UK.
Abstract:
Plant pathogenic bacteria secrete effector proteins that attack the host signaling machinery to suppress immunity. Effectors can be recognized by hosts leading to immunity. One such effector is AvrPtoB of Pseudomonas syringae, which degrades host protein kinases, such as tomato Fen, through an E3 ligase domain. Pto kinase, which is highly related to Fen, recognizes AvrPtoB in conjunction with the resistance protein Prf. Here we show that Pto is resistant to AvrPtoB-mediated degradation because it inactivates the E3 ligase domain. AvrPtoB ubiquitinated Fen within the catalytic cleft, leading to its breakdown and loss of the associated Prf protein. Pto avoids this by phosphorylating and inactivating the AvrPtoB E3 domain. Thus, inactivation of a pathogen virulence molecule is one mechanism by which plants resist disease.
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