Deciphering the plant immune system: PAMP/MAMP perception, signal transduction and manipulation

Abstract

Plants face a constant barrage of microbial threats. The majority of these threats are defeated following detection of conserved microbial molecules (Pathogen-Associated Molecular Patterns, or MAMPs) by host cell surface pattern recognition receptors (PRRs), which activate pattern-triggered immunity (PTI). The load of genome sequence information in Arabidopsis thaliana and the rapid data exploitation through the existence of unique technical resources, place this model plant in a prime position to identify PRRs and to study further the molecular mechanisms underlying immune signaling. As an illustrative example of the utility and tractability of the Arabidopsis model, we identified RLP30, a receptor-like protein involved in the perception of a newly isolated elicitor from Sclerotinia sclerotiorum and conferring partial resistance to necrotrophic fungal pathogens.
 Successful pathogens have evolved effectors that manipulate PTI (effector-triggered susceptibility, ETS). A better understanding of the biology of effector-target interaction is critical to understand the complexity and specificity of the plant immune system. We used a cell-based system that identified a subset of RXLR effectors from Phytophthora infestans suppressing the earliest stages of PTI signaling in the tomato host. This result is reminiscent of PTI suppression by bacterial effectors and shows that eukaryotic effectors have evolved to target similar steps.