Atypical Resistance Protein RPW8/HR Triggers Oligomerization of the NLR Immune Receptor RPP7 and Autoimmunity

Cell Host Microbe. 2020 Mar 11;27(3):405-417.e6. doi: 10.1016/j.chom.2020.01.012. Epub 2020 Feb 25.

Abstract

In certain plant hybrids, immunity signaling is initiated when immune components interact in the absence of a pathogen trigger. In Arabidopsis thaliana, such autoimmunity and cell death are linked to variants of the NLR RPP7 and the RPW8 proteins involved in broad-spectrum resistance. We uncover the molecular basis for this autoimmunity and demonstrate that a homolog of RPW8, HR4Fei-0, can trigger the assembly of a higher-order RPP7 complex, with autoimmunity signaling as a consequence. HR4Fei-0-mediated RPP7 oligomerization occurs via the RPP7 C-terminal leucine-rich repeat (LRR) domain and ATP-binding P-loop. RPP7 forms a higher-order complex only in the presence of HR4Fei-0 and not with the standard HR4 variant, which is distinguished from HR4Fei-0 by length variation in C-terminal repeats. Additionally, HR4Fei-0 can independently form self-oligomers, which directly kill cells in an RPP7-independent manner. Our work provides evidence for a plant resistosome complex and the mechanisms by which RPW8/HR proteins trigger cell death.

Keywords: Arabidopsis thaliana; HELL domain; MLKL; NLR; RPW8/HR; plant immunity.

MeSH terms

  • Arabidopsis / immunology*
  • Arabidopsis Proteins / immunology*
  • Cell Death*
  • Gene Expression Regulation, Plant
  • Plant Immunity*
  • Plants, Genetically Modified
  • Protein Multimerization
  • Tobacco / immunology

Substances

  • Arabidopsis Proteins
  • RPP7 protein, Arabidopsis
  • RPW8.1 protein, Arabidopsis