Large differences in carbohydrate degradation and transport potential among lichen fungal symbionts.

Resl P, Bujold AR, Tagirdzhanova G, Meidl P, Freire Rallo S, Kono M, Fernández-Brime S, Guðmundsson H, Andrésson ÓS, Muggia L, Mayrhofer H, McCutcheon JP, Wedin M, Werth S, Willis LM, Spribille T

Nat Commun 13 (1) 2634 [2022-05-12; online 2022-05-12]

Lichen symbioses are thought to be stabilized by the transfer of fixed carbon from a photosynthesizing symbiont to a fungus. In other fungal symbioses, carbohydrate subsidies correlate with reductions in plant cell wall-degrading enzymes, but whether this is true of lichen fungal symbionts (LFSs) is unknown. Here, we predict genes encoding carbohydrate-active enzymes (CAZymes) and sugar transporters in 46 genomes from the Lecanoromycetes, the largest extant clade of LFSs. All LFSs possess a robust CAZyme arsenal including enzymes acting on cellulose and hemicellulose, confirmed by experimental assays. However, the number of genes and predicted functions of CAZymes vary widely, with some fungal symbionts possessing arsenals on par with well-known saprotrophic fungi. These results suggest that stable fungal association with a phototroph does not in itself result in fungal CAZyme loss, and lends support to long-standing hypotheses that some lichens may augment fixed CO2 with carbon from external sources.

Bioinformatics Support for Computational Resources [Service]

PubMed 35551185

DOI 10.1038/s41467-022-30218-6

Crossref 10.1038/s41467-022-30218-6

pii: 10.1038/s41467-022-30218-6
pmc: PMC9098629
Dryad: 10.5061/dryad.3xsj3txjb