A secreted LysM effector protects fungal hyphae through chitin-dependent homodimer polymerization

PLoS Pathog. 2020 Jun 23;16(6):e1008652. doi: 10.1371/journal.ppat.1008652. eCollection 2020 Jun.

Abstract

Plants trigger immune responses upon recognition of fungal cell wall chitin, followed by the release of various antimicrobials, including chitinase enzymes that hydrolyze chitin. In turn, many fungal pathogens secrete LysM effectors that prevent chitin recognition by the host through scavenging of chitin oligomers. We previously showed that intrachain LysM dimerization of the Cladosporium fulvum effector Ecp6 confers an ultrahigh-affinity binding groove that competitively sequesters chitin oligomers from host immune receptors. Additionally, particular LysM effectors are found to protect fungal hyphae against chitinase hydrolysis during host colonization. However, the molecular basis for the protection of fungal cell walls against hydrolysis remained unclear. Here, we determined a crystal structure of the single LysM domain-containing effector Mg1LysM of the wheat pathogen Zymoseptoria tritici and reveal that Mg1LysM is involved in the formation of two kinds of dimers; a chitin-dependent dimer as well as a chitin-independent homodimer. In this manner, Mg1LysM gains the capacity to form a supramolecular structure by chitin-induced oligomerization of chitin-independent Mg1LysM homodimers, a property that confers protection to fungal cell walls against host chitinases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascomycota / chemistry*
  • Ascomycota / genetics
  • Ascomycota / metabolism
  • Chitin / chemistry*
  • Chitin / genetics
  • Chitin / metabolism
  • Cladosporium / chemistry
  • Cladosporium / genetics
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Hyphae / chemistry*
  • Hyphae / genetics
  • Hyphae / metabolism
  • Plant Diseases / genetics
  • Plant Diseases / microbiology
  • Protein Multimerization*
  • Protein Structure, Quaternary
  • Triticum / genetics
  • Triticum / metabolism
  • Triticum / microbiology

Substances

  • Fungal Proteins
  • Chitin

Grant support

Work in the laboratory of B.P.H.J.T. is supported by the Research Council Earth and Life Sciences (ALW) of the Netherlands Organization of Scientific Research (NWO). Part of the work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany´s Excellence Strategy – EXC 2048/1 – Project ID: 390686111. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.