Functionally Redundant RXLR Effectors from Phytophthora infestans Act at Different Steps to Suppress Early flg22-Triggered Immunity

PLoS Pathogens

Frédéric Brunner¹  Eleanor M. Gilroy¹  Petra C. Boevink¹  Xiaoyu Liu²  Xiangzi Zheng²  Malou Fraiture²  Ying Chen²  Guido Sessa³  Kabindra Kandel⁴  Paul R. J. Birch⁴  Hazel McLellan⁴ 

[1] Cell and Molecular Sciences, The James Hutton Institute, University of Dundee, Invergowrie, Dundee, United Kingdom;Department of Biochemistry, Centre for Plant Molecular Biology, Eberhard Karls University, Tübingen, Germany;Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, Israel;Division of Plant Sciences, University of Dundee (at James Hutton Institute), Invergowrie, Dundee, United Kingdom

关键词: Arabidopsis thaliana;    Tomatoes;    MAMP-triggered immunity;    Gene expression;    Cell death;    Leaves;    In vitro kinase assay;    Plants;   

DOI  :  10.1371/journal.ppat.1004057

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Genome sequences of several economically important phytopathogenic oomycetes have revealed the presence of large families of so-called RXLR effectors. Functional screens have identified RXLR effector repertoires that either compromise or induce plant defense responses. However, limited information is available about the molecular mechanisms underlying the modes of action of these effectors in planta. The perception of highly conserved pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), such as flg22, triggers converging signaling pathways recruiting MAP kinase cascades and inducing transcriptional re-programming, yielding a generic anti-microbial response. We used a highly synchronizable, pathogen-free protoplast-based assay to identify a set of RXLR effectors from Phytophthora infestans (PiRXLRs), the causal agent of potato and tomato light blight that manipulate early stages of flg22-triggered signaling. Of thirty-three tested PiRXLR effector candidates, eight, called Suppressor of early Flg22-induced Immune response (SFI), significantly suppressed flg22-dependent activation of a reporter gene under control of a typical MAMP-inducible promoter (pFRK1-Luc) in tomato protoplasts. We extended our analysis to Arabidopsis thaliana, a non-host plant species of P. infestans. From the aforementioned eight SFI effectors, three appeared to share similar functions in both Arabidopsis and tomato by suppressing transcriptional activation of flg22-induced marker genes downstream of post-translational MAP kinase activation. A further three effectors interfere with MAMP signaling at, or upstream of, the MAP kinase cascade in tomato, but not in Arabidopsis. Transient expression of the SFI effectors in Nicotiana benthamiana enhances susceptibility to P. infestans and, for the most potent effector, SFI1, nuclear localization is required for both suppression of MAMP signaling and virulence function. The present study provides a framework to decipher the molecular mechanisms underlying the manipulation of host MAMP-triggered immunity (MTI) by P. infestans and to understand the basis of host versus non-host resistance in plants towards P. infestans.

【 授权许可】

CC BY