Genomic analysis of Ancylistes closterii, an enigmatic alga parasitic fungus in the arthropod-associated Entomophthoromycotina.

Recent advances in fungal genome sequencing have dramatically altered our understanding of the phylogeny and evolution of Fungi. However, there are still many poorly studied obligate parasitic or symbiotic fungi for which we lack any genomic information or knowledge of where they fit in the fungal phylogeny. Ancylistes, an endoparasite of desmid green algae, is such an understudied fungal genus that is classified among Entomophthoromycotina in Zoopagomycota on the basis of morphology. However, this relationship is perplexing, because Zoopagomycota is almost entirely composed of animal-associated fungi. In this study, we found and cultivated Ancylistes closterii with its green algal host Closterium sp. and sequenced its genome to investigate its phylogenetic position and evolution. Phylogenetic analyses using rDNA and genome-scale data sets showed that A. closterii was sister to other Entomophthoromycotina fungi, confirming the taxonomic position of Ancylistes. Despite the ecological distinctiveness between Ancylistes and other Entomophthoromycotina fungi, our comparative genomic analyses revealed shared traits of these fungi such as lineage-specific subtilases and hybrid histidine kinases. Ancylistes also possessed unique genes among Zoopagomycota fungi such as plant cell wall-degrading enzymes that could be important for infection of algae.