Protein phosphorylation in plant immunity: insights into the regulation of pattern recognition receptor-mediated signaling

Chang-Jin Park,Daniel F Caddell,Pamela C Ronald

doi:10.3389/fpls.2012.00177

Abstract

Plants are continuously challenged by pathogens including viruses, bacteria, and fungi. The plant immune system recognizes invading pathogens and responds by activating an immune response. These responses occur rapidly and often involve post-translational modifications (PTMs) within the proteome. Protein phosphorylation is a common and intensively studied form of these PTMs and regulates many plant processes including plant growth, development, and immunity. Most well-characterized pattern recognition receptors (PRRs), including Xanthomonas resistance 21, flagellin sensitive 2, and elongation factor-Tu receptor, possess intrinsic protein kinase activity and regulate downstream signaling through phosphorylation events. Here, we focus on the phosphorylation events of plant PRRs that play important roles in the immune response. We also discuss the role of phosphorylation in regulating mitogen-associated protein kinase cascades and transcription factors in plant immune signaling.

Highlights

Proteins can undergo various post-translational modifications (PTMs) that affect their conformation, activity, stability, and localization
In Arabidopsis, more than 1,170 phosphopeptides from 472 phosphoproteins were identified after treatments with flg22 or xylanase, both of which elicit immune responses in Arabidopsis cell cultures (Benschop et al, 2007). These results indicate that many proteins are differentially phosphorylated and that the phosphorylation events are essential to both animal and plant immune responses
We focus primarily on phosphorylation events mediated by plant pattern recognition receptors (PRRs) that play important roles in the immune response

Summary

INTRODUCTION

Proteins can undergo various post-translational modifications (PTMs) that affect their conformation, activity, stability, and localization. We focus primarily on phosphorylation events mediated by plant pattern recognition receptors (PRRs) that play important roles in the immune response. In Arabidopsis, two additional plant PRRs have been well-characterized These are flagellin sensitive 2 (FLS2) and elongation factor (EF)-Tu receptor (EFR), which recognize the flg peptide from flagellated bacteria and the EF-Tu-derived peptide elf, respectively (Gomez-Gomez and Boller, 2000; Zipfel et al, 2006). The rice ortholog of BAK1, XA21-associated kinase 1 (XAK1), is required for XA21-mediated immunity (Chen et al, unpublished) These results demonstrate that PRRs utilize coregulatory receptors carrying RD kinases as signaling partners to transduce the immune response.

Protein class

CONCLUSION AND PERSPECTIVES