PT  - JOURNAL ARTICLE
AU  - Feng Zhang
AU  - Aurore Labourel
AU  - Mireille Haon
AU  - Minna Kemppainen
AU  - Emilie Da Silva Machado
AU  - Nicolas Brouilly
AU  - Claire Veneault-Fourrey
AU  - Annegret Kohler
AU  - Marie-Noëlle Rosso
AU  - Alejandro Pardo
AU  - Bernard Henrissat
AU  - Jean-Guy Berrin
AU  - Francis Martin
TI  - The ectomycorrhizal basidiomycete <em>Laccaria bicolor</em> releases a GH28 polygalacturonase that plays a key role in symbiosis establishment
AID  - 10.1101/2021.09.24.461608
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.09.24.461608
4099  - http://biorxiv.org/content/early/2021/09/24/2021.09.24.461608.short
4100  - http://biorxiv.org/content/early/2021/09/24/2021.09.24.461608.full
AB  - In ectomycorrhiza, root penetration and colonization of the intercellular space by symbiotic hyphae is thought to rely on the mechanical force that results from hyphal tip growth, enhanced by the activity of secreted cell-wall-degrading enzymes.Here, we characterize the biochemical properties of the symbiosis-induced polygalacturonase LbGH28A from the ectomycorrhizal fungus Laccaria bicolor. The transcriptional regulation of LbGH28A was measured by qPCR. The biological relevance of LbGH28A was confirmed by generating RNAi-silenced LbGH28A mutants. We localized the LbGH28A protein by immunofluorescence confocal and immunogold cytochemical microscopy in poplar ectomycorrhizal roots.qPCR confirmed the induced expression of LbGH28A during ectomycorrhiza formation. L. bicolor RNAi mutants have a lower ability to establish ectomycorrhiza confirming the key role of this enzyme in symbiosis. The purified recombinant LbGH28A has its highest activity towards pectin and polygalacturonic acid. In situ localization of LbGH28A indicates that this endopolygalacturonase is located in both fungal and plant cell walls at the symbiotic hyphal front.The present findings suggest that the symbiosis-induced pectinase LbGH28A is involved in the Hartig net formation and is an important determinant for successful symbiotic colonization.Competing Interest StatementThe authors have declared no competing interest.