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Eudicot plant-specific sphingolipids determine host selectivity of microbial NLP cytolysins

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Science  15 Dec 2017:
Vol. 358, Issue 6369, pp. 1431-1434
DOI: 10.1126/science.aan6874

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An extra sugar protects

Many microbial pathogens produce proteins that are toxic to the cells that they are targeting. Broad-leaved plants are susceptible to NLP (necrosis and ethylene-inducing peptide 1–like protein) toxins. Lenarčič et al. identified the receptors for NLP toxins to be GIPC (glycosylinositol phosphorylceramide) sphingolipids (see the Perspective by Van den Ackerveken). Their findings reveal why these toxins only attack broad-leaved plants (so-called eudicots): If the sphingolipid carries just two hexoses, as is the case for eudicots, the toxin binds and causes cell lysis. But in monocots with sphingolipids that have three hexoses, the toxin is ineffective.

Science, this issue p. 1431; see also p. 1383

Abstract

Necrosis and ethylene-inducing peptide 1–like (NLP) proteins constitute a superfamily of proteins produced by plant pathogenic bacteria, fungi, and oomycetes. Many NLPs are cytotoxins that facilitate microbial infection of eudicot, but not of monocot plants. Here, we report glycosylinositol phosphorylceramide (GIPC) sphingolipids as NLP toxin receptors. Plant mutants with altered GIPC composition were more resistant to NLP toxins. Binding studies and x-ray crystallography showed that NLPs form complexes with terminal monomeric hexose moieties of GIPCs that result in conformational changes within the toxin. Insensitivity to NLP cytolysins of monocot plants may be explained by the length of the GIPC head group and the architecture of the NLP sugar-binding site. We unveil early steps in NLP cytolysin action that determine plant clade-specific toxin selectivity.

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