A truncated NLR protein, TIR-NBS2, is required for activated defense responses in the exo70B1 mutant

PLoS Genet. 2015 Jan 24;11(1):e1004945. doi: 10.1371/journal.pgen.1004945. eCollection 2015 Jan.

Abstract

During exocytosis, the evolutionarily conserved exocyst complex tethers Golgi-derived vesicles to the target plasma membrane, a critical function for secretory pathways. Here we show that exo70B1 loss-of-function mutants express activated defense responses upon infection and express enhanced resistance to fungal, oomycete and bacterial pathogens. In a screen for mutants that suppress exo70B1 resistance, we identified nine alleles of TIR-NBS2 (TN2), suggesting that loss-of-function of EXO70B1 leads to activation of this nucleotide binding domain and leucine-rich repeat-containing (NLR)-like disease resistance protein. This NLR-like protein is atypical because it lacks the LRR domain common in typical NLR receptors. In addition, we show that TN2 interacts with EXO70B1 in yeast and in planta. Our study thus provides a link between the exocyst complex and the function of a 'TIR-NBS only' immune receptor like protein. Our data are consistent with a speculative model wherein pathogen effectors could evolve to target EXO70B1 to manipulate plant secretion machinery. TN2 could monitor EXO70B1 integrity as part of an immune receptor complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / immunology
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / biosynthesis
  • Arabidopsis Proteins / genetics*
  • Cell Death / genetics
  • Disease Resistance / genetics*
  • Disease Resistance / immunology
  • Exocytosis / genetics
  • Gene Expression Regulation, Plant
  • Immunoprecipitation
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mutation
  • Phenotype
  • Plant Diseases / genetics*
  • Plant Diseases / microbiology
  • Plant Immunity / genetics*
  • Plant Leaves / genetics
  • Plant Leaves / immunology
  • Plant Leaves / microbiology
  • Signal Transduction
  • Vesicular Transport Proteins / biosynthesis
  • Vesicular Transport Proteins / genetics*

Substances

  • Arabidopsis Proteins
  • EXO70B1 protein, Arabidopsis
  • Membrane Proteins
  • Vesicular Transport Proteins

Grant support

The work was supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB11020100), National Basic Research Program of China (2015CB910200) to DT and the National Natural Science Foundation of China (31071067) to TZ. This work was also funded by grants to JLD from the National Science Foundation IOS-1257373 and by the HHMI and the Gordon and Betty Moore Foundation (GBMF3030). JLD is an Investigator of the Howard Hughes Medical Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.