Biology subjects

Kemppainen, M.

Publications and source records attributed to Kemppainen, M..

3 recordsLinked to original sources

bioRxiv2022

Laccaria bicolor pectin methylesterases are involved in ectomycorrhiza development with Populus tremula x Populus tremuloides

O_LIThe development of ectomycorrhizal (ECM) symbioses between soil fungi and tree roots requires modification of root cell-walls. The pectin-mediated adhesion between adjacent root cells loosens to accommodate fungal hyphae in the Hartig Net, facilitating nutrient exchange between partners. We investigated the role of fungal pectin modifying enzymes in Laccaria bicolor for ECM formation with Populus tremula x Populus tremuloides. C_LIO_LIWe combine transcriptomics of cell-wall related enzymes in both partners during ECM formation, immunolocalization of pectin (Homogalacturonan, HG) epitopes in different methylesterification states, pectin methylesterase (PME) activity assays and functional analyses of transgenic L. bicolor to uncover pectin modification mechanisms and the requirement of fungal pectin methylesterases (LbPMEs) for ECM formation. C_LIO_LIImmunolocalization identified remodelling of pectin towards de-esterified HG during ECM formation, which was accompanied by increased LbPME1 expression and PME activity. Overexpression or RNAi of the ECM-induced LbPME1 in transgenic L. bicolor lines led to reduced ECM formation. Hartig Nets formed with LbPME1 RNAi lines were shallower, whereas those formed with LbPME1 over-expressors were deeper. C_LIO_LIThis suggests that LbPME1 plays a role in ECM formation potentially through HG-de-esterification, which initiates loosening of adjacent root cells to facilitate Hartig Net formation. C_LI

plant biology↗

bioRxiv2021

The ectomycorrhizal basidiomycete Laccaria bicolor releases a GH28 polygalacturonase that plays a key role in symbiosis establishment

O_LIIn 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. C_LIO_LIHere, 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. C_LIO_LIqPCR 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. C_LIO_LIThe 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. C_LI

plant biology↗

bioRxiv2017

Laccaria bicolor MiSSP8 is a small-secreted protein decisive for the establishment of the ectomycorrhizal symbiosis

The ectomycorrhizal symbiosis is a predominant tree-microbe interaction in forest ecosystems sustaining tree growth and health. Its establishment and functioning implies a long-term and intimate relationship between the soil-borne fungi and the roots of trees. Mycorrhiza-induced Small Secreted Proteins (MiSSPs) are hypothesized as keystone symbiotic proteins, required to set up the symbiosis by modifying the host metabolism and/or building the symbiotic interfaces.\n\nL. bicolor MiSSP8 is the third most highly induced MiSSPs in symbiotic tissues and it is also expressed in fruiting bodies. The MiSSP8-RNAi knockdown mutants are strongly impaired in their mycorrhization ability with Populus, with the lack of fungal mantle and Hartig net development due to a lack of hyphal aggregation. MiSSP8 C-terminus displays a repetitive motif containing a kexin cleavage site, recognized by KEX2 in vitro. This suggests MiSSP8 protein might be cleaved into small peptides. Moreover, the MiSSP8 repetitive motif is found in other proteins predicted secreted by both saprotrophic and ectomycorrhizal fungi. Thus, our data indicate that MiSSP8 is a small-secreted protein involved at early stages of ectomycorrhizal symbiosis, likely by regulating hyphal aggregation and pseudoparenchyma formation.

plant biology↗