Basidiomycete yeasts in the cortex of ascomycete macrolichens

TLDR

Lichens are composed of three distinct parts, and laboratory co‑culture of the plant and fungal partners cannot reproduce their natural growth forms. The study shows that North American beard‑like lichens are tripartite symbioses—an ascomycete fungus, a photosynthetic alga, and a basidiomycete yeast that forms the cortex and is essential for lichen shape, overturning the traditional binary model. Spribille et al.

Abstract

Lichens assemble in three parts Lichen growth forms cannot be recapitulated in the laboratory by culturing the plant and fungal partners together. Spribille et al. have discovered that the classical binary view of lichens is too simple. Instead, North American beard-like lichens are constituted of not two but three symbiotic partners: an ascomycetous fungus, a photosynthetic alga, and, unexpectedly, a basidiomycetous yeast. The yeast cells form the characteristic cortex of the lichen thallus and may be important for its shape. The yeasts are ubiquitous and essential partners for most lichens and not the result of lichens being colonized or parasitized by other organisms. Science , this issue p. 488