Whole-genome sequence of the lichen-forming fungus Cetrariella delisei reveals an expanded repertoire of biosynthetic gene clusters

Lichens represent a distinctive symbiotic relationship between fungi and photosynthetic algae, allowing them to persist in harsh and extreme habitats. While known for their adaptability, the genomic features of lichen-forming fungi remain relatively understudied. In this study, the genome of the lichen-forming fungus Cetrariella delisei was assembled into 40 contigs, spanning 45.8 Mbp, with a BUSCO completeness of 96.7 %. Repetitive sequences comprised 18.14 % of the genome. A total of 11,716 genes were annotated, including 401 putative carbohydrate-active enzymes (CAZymes), though polysaccharide lyases were absent. Comparative analysis with five additional Parmeliaceae species showed that C. delisei contains a markedly higher number of auxiliary activity genes. Notably, C. delisei harbors 79 biosynthetic gene clusters (BGCs), exceeding the 50 to 65 clusters typically observed in related species, reflecting an expanded biosynthetic repertoire potentially underlying enhanced natural product diversity. These results improve our understanding of lichen symbiosis and provide a valuable genomic resource for future research.