Mutational analysis of the Ve1 immune receptor that mediates Verticillium resistance in tomato.

Zhao Zhang,Yin Song,Chun-Ming Liu,Bart P H J Thomma,Boris Alexander Vinatzer

doi:10.1371/journal.pone.0099511

Abstract

Pathogenic Verticillium species are economically important plant pathogens that cause vascular wilt diseases in hundreds of plant species. The Ve1 gene of tomato confers resistance against race 1 strains of Verticillium dahliae and V. albo-atrum. Ve1 encodes an extracellular leucine-rich repeat (eLRR) receptor-like protein (RLP) that serves as a cell surface receptor for recognition of the recently identified secreted Verticillium effector Ave1. To investigate recognition of Ave1 by Ve1, alanine scanning was performed on the solvent exposed β-strand/β-turn residues across the eLRR domain of Ve1. In addition, alanine scanning was also employed to functionally characterize motifs that putatively mediate protein-protein interactions and endocytosis in the transmembrane domain and the cytoplasmic tail of the Ve1 protein. Functionality of the mutant proteins was assessed by screening for the occurrence of a hypersensitive response upon co-expression with Ave1 upon Agrobacterium tumefaciens-mediated transient expression (agroinfiltration). In order to confirm the agroinfiltration results, constructs encoding Ve1 mutants were transformed into Arabidopsis and the transgenes were challenged with race 1 Verticillium. Our analyses identified several regions of the Ve1 protein that are required for functionality.

Highlights

In order to activate immune responses that ward off invading microorganisms, plants utilize various types of receptors that recognize pathogen(-induced) ligands of various nature [1,2]
Site-directed mutagenesis has been employed for functional analysis of extracellular leucine-rich repeat (eLRR)-containing cell surface receptors
Recently reported site-directed mutations proved that the Cys residues in the Nterminal flanking region of the flagellin-sensitive 2 (FLS2) eLRRs are required for protein stability and function [33]

Summary

Introduction

In order to activate immune responses that ward off invading microorganisms, plants utilize various types of receptors that recognize pathogen(-induced) ligands of various nature [1,2]. Appropriate recognition of these ligands by the immune receptors is crucial for the activation of immune responses These immune receptors are either extracellular cell surface receptors that detect (conserved) pathogen-associated molecular patterns (PAMPs) or damage-associated modified self-patterns, or cytoplasmic receptors that recognize highly specific pathogen effectors either directly, or indirectly through recognition of their activities [3,4]. Both types of receptors may activate an hypersensitive response (HR), which is a rapid cell death surrounding the infection site that is thought to prevent further pathogen invasion [5]. An acidic domain is present between the eLRR domain and the TM domain

Methods

Results

Conclusion