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

Resl, Philipp; Bujold, Adina R.; Tagirdzhanova, Gulnara; Meidl, Peter; Rallo, Sandra Freire; Kono, Mieko; Fernandez-Brime, Samantha; Gudmundsson, Hordur; Andresson, Olafur Sigmar; Muggia, Lucia; Mayrhofer, Helmut; McCutcheon, John P.; Wedin, Mats; Werth, Silke; Willis, Lisa M. and Spribille, Toby (2022): Large differences in carbohydrate degradation and transport potential among lichen fungal symbionts. In: Nature Communications, Vol. 13, No. 1, 2634

Abstract

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. Lichen symbioses are thought to be stabilized by the transfer of fixed carbon from a photosynthesizing symbiont to a fungus. Here, Resl et al. show that, contrary to other fungal symbioses, fungal association with a phototroph in lichens does not result in loss of fungal enzymes for plant cell-wall degradation.

• Item Type: Journal article
• Faculties: Biology
• Subjects: 500 Science > 570 Life sciences; biology
• Language: English