Pseudomonas syringae Effector AvrPto Blocks Innate Immunity by Targeting Receptor Kinases

Abstract

Plants use receptor kinases, such as FLS2 and EFR, to perceive bacterial pathogens and initiate innate immunity. This immunity is often suppressed by bacterial effectors, allowing pathogen propagation. To counteract, plants have evolved disease resistance genes that detect the bacterial effectors and reinstate resistance. The Pseudomonas syringae effector AvrPto promotes infection in susceptible plants but triggers resistance in plants carrying the protein kinase Pto and the associated resistance protein Prf. Here we show that AvrPto binds receptor kinases, including Arabidopsis FLS2 and EFR and tomato LeFLS2, to block plant immune responses in the plant cell. The ability to target receptor kinases is required for the virulence function of AvrPto in plants. The FLS2-AvrPto interaction and Pto-AvrPto interaction appear to share similar sequence requirements, and Pto competes with FLS2 for AvrPto binding. The results suggest that the mechanism by which AvrPto recognizes virulence targets is linked to the evolution of Pto, which, in association with Prf, recognizes the bacterium and triggers strong resistance.

Crystal Structure of the Complex between Pseudomonas Effector AvrPtoB and the Tomato Pto Kinase Reveals Both a Shared and a Unique Interface Compared with AvrPto-Pto

“…Binding of AvrPto by Pto might then interfere with the ability of the effector to disrupt PTI (Xing et al, 2007). Indeed, it was shown recently that AvrPto interacts with the kinase domains of both FLS2/EFR1 from Arabidopsis and inhibits their kinase activity that is needed for PTI (Xiang et al, 2008). Moreover, both the FLS2 kinase domain and Pto bind AvrPto in a competitive manner, supporting structural similarity between FLS2-AvrPto and Pto-AvrPto interaction (Xiang et al, 2008).…”

“…Indeed, it was shown recently that AvrPto interacts with the kinase domains of both FLS2/EFR1 from Arabidopsis and inhibits their kinase activity that is needed for PTI (Xiang et al, 2008). Moreover, both the FLS2 kinase domain and Pto bind AvrPto in a competitive manner, supporting structural similarity between FLS2-AvrPto and Pto-AvrPto interaction (Xiang et al, 2008). Interestingly, AvrPto also appears to bind BAK1 (Shan et al, 2008), a protein required for FLS2 and EFR1 function (Chinchilla et al, 2007;Heese et al, 2007).…”

Plant defense response against Fusarium oxysporum and strategies to develop tolerant genotypes in banana

“…It has been revealed that mutation in FeRONIA (FeR), a CrRLK, leads to spontaneous H 2 O 2 production and cell death, resulting in PM resistance and aberrant pollen tube reception (Kessler et al 2010). Interaction of another related RLK, At2g23200 in yeast two-hybrid assays with the Pseudomonas syringae effector AvrPto showed that its expression was regulated by a number of PAMPs, pathogen-secreted molecules that regulate infection and triggers immunity (Xiang et al 2008). ANXUR 1 and ANXUR 2 which are RLKs help in cell wall integrity and are homologous to FeR, but have opposite functions to FeR (Boisson-Dernier et al 2009;Miyazaki et al 2009).…”

Pseudomonas syringae type III effector HopAF1 suppresses plant immunity by targeting methionine recycling to block ethylene induction

“…T3Es commonly contain sequences addressing specific eukaryotic subcellular localizations (10,11) and enzymatic activities (12)(13)(14)(15)(16)(17) that disrupt and/or suppress PTI. Known targets of T3Es include plasma membrane-localized receptor complexes (13,(18)(19)(20)(21)(22)(23), downstream MAPK cascades (24,25), the stability of defenserelated transcripts (26), phytoalexin biosynthesis (27), and vesicle trafficking (28).…”