The tomato Prf complex is a molecular trap for bacterial effectors based on Pto transphosphorylation

Area of Science:

• Plant-pathogen interactions
• Molecular plant pathology
• Plant immunity

Background:

• Phytopathogenic bacteria deliver effector proteins into host cells to disrupt immune responses.
• AvrPto and AvrPtoB from Pseudomonas syringae target conserved receptor-kinases in plants.
• Tomato utilizes the Pto/Prf intracellular complex to recognize these bacterial effectors.

Purpose of the Study:

• To elucidate the molecular mechanism by which the Pto/Prf complex recognizes and responds to AvrPto and AvrPtoB.
• To understand how bacterial effectors targeting protein kinases are detected by the host.
• To investigate the role of the Pto P+1 loop in effector recognition and defense activation.

Main Methods:

• Biochemical approaches
• Structural analyses of effector-Pto interactions
• In vitro kinase assays

Main Results:

• AvrPto and AvrPtoB interact with the Pto P+1 loop.
• Disruption of the Pto P+1 loop triggers trans-phosphorylation within the oligomeric Pto/Prf complex.
• Both P+1 loop perturbation and trans-phosphorylation are essential for initiating defense signaling.

Conclusions:

• The Pto/Prf complex functions as a sophisticated molecular trap for bacterial protein kinase-targeting effectors.
• Effector binding to one kinase molecule within the complex activates signaling through another.
• This mechanism highlights the co-evolutionary arms race between bacterial virulence strategies and host immune recognition.