Dermatophytes and mammalian hair: aspects of the evolution of Arthrodermataceae

Abstract

Dermatophytes and other members of Onygenales are unique in their ability to degrade keratin, affecting hair and nails, and in the case of human hosts, causing skin infections. Subtillisins are essential proteases in keratin assimilation, and subtilisin-like protease 1 (SUB1) and SUB3–7 are specific for dermatophytes. eIF2α kinases are serine-threonine kinases that perform essential functions in response to infection, proteotoxicity, and nutrient scavenging. The relatively conserved nature of EIF2AK4 among fungi makes them potential evolutionary markers, which may contribute to a deeper understanding of dermatophyte taxonomy and evolution. This study aimed to assess the phylogeny of dermatophytes by examining the EIF2AK4 and SUB1 genes compared to the ITS gene marker. The phylogenetic trees generated from the EIF2AK4 and SUB1 genes exhibited a similar topology, which differed from that observed in the ITS tree. Our preliminary findings with a limited dataset suggest that the EIF2AK4 and SUB1 genes provide a reasonably correct reflection of the evolution of Arthrodermataceae. In addition, the study analyzed in vitro keratinolytic responses of 19 dermatophyte species using hairs of a broad range of mammals, including ancestral as well as derived species, as substrates. Trichophyton mentagrophytes and Nannizzia gypsea were the most active in degrading hair, while Trichophyton verrucosum, Trichophyton tonsurans and Epidermophyton floccosum showed low response. Hairs of Hyracoidea and Rodentia were most affected of all mammal hairs, while in contrast, bat hairs were difficult to degrade by nearly all tested dermatophyte species. Zoophilic species showed more activity than anthropophilic dermatophytes, but hair degradation profiles were not diagnostic for particular dermatophyte species.