Photo Credit: Mark Steinmetz

The genome of Crucibulum laeve (Nidulariaceae, Agaricales) has been sequenced as part of the 1000 Fungal Genomes Project. Crucibulum belongs to a small family containing bird’s nest fungi, which are characterized by unusual, urn-shaped fruiting bodies that contain black, disc-shaped reproductive structures, called peridioles. Peridioles contain basidia and basidiospores and are spread by falling raindrops. This unusual way of spore dispersal makes them somewhat similar to puffballs (e.g. Lycoperdon and Bovista spp.), however, unlike puffballs, where clouds of spores are released by raindrops, peridioles of bird’s nest fungi are expelled as a whole by falling raindrops. Bird’s nest fungi colonize dead woody materials, nutrient-rich soil or dung. Wood-inhabiting species of the family cause white rot on the colonized wood; their lignocellulose-degrading enzymes have been subject to intense research.
Bird’s nest fungi have internally developing spores, which has led mycologists classify them in the Gasteromycetes (puffballs in a wide sense) in the past. However, molecular studies based on nuclear and mitochondrial ribosomal DNA revealed that they belong to the Agaricales, where their exact affinities have remained unknown. Its position within the Agaricales implies that their unique fruiting body morphology likely evolved from agaricoid ancestors (mushrooms with can and stalk), through a complete loss of cap, stipe and other structures commonly found in mushrooms. It is difficult to recognize homology relationships between tissue types of bird’s nest fungi and ‘ordinary’ mushrooms, which makes the evolution of bird’s nest fungi one of the most intriguing morphological transformations in mushroom-forming fungi. The Crucibulum laeve genome will help to unravel the evolutionary origins of this unusual fruiting body morphology within agaricoid fungi.