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Distinct regions of the Pseudomonas syringae coiled-coil effector AvrRps4 are required for activation of immunity

DOI: 10.1073/pnas.1212332109 DOI Help
PMID: 22988101 PMID Help

Authors: K. H. Sohn (The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK) , R. K. Hughes (Department of Biological Chemistry, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK) , S. J. Piquerez (The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK) , J. D. G. Jones (The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK) , M. J. Banfield (Department of Biological Chemistry, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences

State: Published (Approved)
Published: September 2012
Diamond Proposal Number(s): 1219

Abstract: Gram-negative phytopathogenic bacteria translocate effector proteins into plant cells to subvert host defenses. These effectors can be recognized by plant nucleotide-binding–leucine-rich repeat immune receptors, triggering defense responses that restrict pathogen growth. AvrRps4, an effector protein from Pseudomonas syringae pv. pisi, triggers RPS4-dependent immunity in resistant accessions of Arabidopsis. To better understand the molecular basis of AvrRps4-triggered immunity, we determined the crystal structure of processed AvrRps4 (AvrRps4C, residues 134–221), revealing that it forms an antiparallel α-helical coiled coil. Structure-informed mutagenesis reveals an electronegative surface patch in AvrRps4C required for recognition by RPS4; mutations in this region can also uncouple triggering of the hypersensitive response from disease resistance. This uncoupling may result from a lower level of defense activation, sufficient for avirulence but not for triggering a hypersensitive response. Natural variation in AvrRps4 reveals distinct recognition specificities that involve a surface-exposed residue. Recently, a direct interaction between AvrRps4 and Enhanced Disease Susceptibility 1 has been implicated in activation of immunity. However, we were unable to detect direct interaction between AvrRps4 and Enhanced Disease Susceptibility 1 after coexpression in Nicotiana benthamiana or in yeast cells. How intracellular plant immune receptors activate defense upon effector perception remains an unsolved problem. The structure of AvrRps4C, and identification of functionally important residues for its activation of plant immunity, advances our understanding of these processes in a well-defined model pathosystem.

Journal Keywords: Arabidopsis; Bacterial; DNA; DNA-Binding; Genetic; Immunoblotting; Microscopy; Confocal; Models; Molecular; Mutagenesis; Site-Directed; Plasmids; Protein; Pseudomonas; Tobacco; Two-Hybrid; Ultracentrifugation; Yeasts

Subject Areas: Biology and Bio-materials, Environment, Medicine


Instruments: I02-Macromolecular Crystallography , I04-Macromolecular Crystallography