Discovery of a Family of Mixed Lineage Kinase Domain-like Proteins in Plants and Their Role in Innate Immune Signaling

Lisa K. Mahdi, Menghang Huang, Xiaoxiao Zhang, Ryohei Thomas Nakano, Leïla Brulé Kopp, Isabel M.L. Saur, Florence Jacob, Viera Kovacova, Dmitry Lapin, Jane E. Parker, James M. Murphy, Kay Hofmann, Paul Schulze-Lefert, Jijie Chai, Takaki Maekawa*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

HeLo domain-containing mixed lineage kinase domain-like protein (MLKL), a pseudokinase, mediates necroptotic cell death in animals. Here, we report the discovery of a conserved protein family across seed plants that structurally resembles vertebrate MLKL. The Arabidopsis genome encodes three MLKLs (AtMLKLs) with overlapping functions in disease resistance mediated by Toll-interleukin 1-receptor domain intracellular immune receptors (TNLs). The HeLo domain of AtMLKLs confers cell death activity but is dispensable for immunity. Cryo-EM structures reveal a tetrameric configuration, in which the HeLo domain is buried, suggestive of an auto-repressed complex. The mobility of AtMLKL1 along microtubules is reduced by chitin, a fungal immunity-triggering molecule. An AtMLKL1 phosphomimetic variant exhibiting reduced mobility enhances immunity. Coupled with the predicted presence of HeLo domains in plant helper NLRs, our data reveal the importance of HeLo domain proteins for TNL-dependent immunity and argue for a cell death-independent immune mechanism mediated by MLKLs.

Original languageEnglish
Pages (from-to)813-824
JournalCell Host and Microbe
Volume28
Issue number6
DOIs
Publication statusPublished - 9 Dec 2020
Externally publishedYes

Keywords

  • Cell death
  • cryo-electron microscopy structures
  • HeLo domain
  • microtubules
  • MLKL
  • necroptosis
  • toll-interleukin1-receptor domain intracellular immune receptors

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