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The ectomycorrhizal basidiomycete Laccaria bicolor releases a secreted β‐1,4 endoglucanase that plays a key role in symbiosis development
Author(s) -
Zhang Feng,
Anasontzis George E.,
Labourel Aurore,
Champion Charlotte,
Haon Mireille,
Kemppainen Minna,
Commun Carine,
Deveau Aurélie,
Pardo Alejandro,
VeneaultFourrey Claire,
Kohler Annegret,
Rosso MarieNoëlle,
Henrissat Bernard,
Berrin JeanGuy,
Martin Francis
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.15113
Subject(s) - ectomycorrhiza , biology , expansin , symbiosis , cell wall , hypha , microbiology and biotechnology , cellulase , apoplast , mycorrhiza , biochemistry , gene expression , gene , cellulose , botany , genetics , bacteria
Summary In ectomycorrhiza, root ingress and colonization of the apoplast by colonizing hyphae is thought to rely mainly on the mechanical force that results from hyphal tip growth, but this could be enhanced by secretion of cell‐wall‐degrading enzymes, which have not yet been identified. The sole cellulose‐binding module ( CBM 1) encoded in the genome of the ectomycorrhizal Laccaria bicolor is linked to a glycoside hydrolase family 5 ( GH 5) endoglucanase, Lb GH 5‐ CBM 1. Here, we characterize Lb GH 5‐ CBM 1 gene expression and the biochemical properties of its protein product. We also immunolocalized Lb GH 5‐ CBM 1 by immunofluorescence confocal microscopy in poplar ectomycorrhiza. We show that Lb GH 5‐ CBM 1 expression is substantially induced in ectomycorrhiza, and RNA i mutants with a decreased Lb GH 5‐ CBM 1 expression have a lower ability to form ectomycorrhiza, suggesting a key role in symbiosis. Recombinant Lb GH 5‐ CBM 1 displays its highest activity towards cellulose and galactomannans, but no activity toward L. bicolor cell walls. In situ localization of Lb GH 5‐ CBM 1 in ectomycorrhiza reveals that the endoglucanase accumulates at the periphery of hyphae forming the Hartig net and the mantle. Our data suggest that the symbiosis‐induced endoglucanase Lb GH 5‐ CBM 1 is an enzymatic effector involved in cell wall remodeling during formation of the Hartig net and is an important determinant for successful symbiotic colonization.