Organization and Evolutionary Trajectory of the Mating Type ( MAT ) Locus in Dermatophyte and Dimorphic Fungal Pathogens

Sexual reproduction in fungi is governed by a specialized genomic region, the mating type (MAT ) locus, whose gene identity, organization, and complexity are diverse. We identified theMAT locus of five dermatophyte fungal pathogens (Microsporum gypseum ,Microsporum canis ,Trichophyton equinum ,Trichophyton rubrum , andTrichophyton tonsurans ) and a dimorphic fungus,Paracoccidioides brasiliensis , and performed phylogenetic analyses. The identifiedMAT locus idiomorphs ofM. gypseum control cell type identity in mating assays, and recombinant progeny were produced. Virulence tests inGalleria mellonella larvae suggest the two mating types ofM. gypseum may have equivalent virulence. Synteny analysis revealed common features of theMAT locus shared among these five dermatophytes: namely, a small size (∼3 kb) and a novel gene arrangement. TheSLA2 ,COX13 , andAPN2 genes, which flank theMAT locus in otherAscomycota are instead linked on one side of the dermatophyteMAT locus. In addition, the transcriptional orientations of theAPN2 andCOX13 genes are reversed compared to the dimorphic fungiHistoplasma capsulatum ,Coccidioides immitis , andCoccidioides posadasii . A putative transposable element,pogo , was found to have inserted in theMAT1-2 idiomorph of oneP. brasiliensis strain but not others. In conclusion, the evolution of theMAT locus of the dermatophytes and dimorphic fungi from the last common ancestor has been punctuated by both gene acquisition and expansion, and asymmetric gene loss. These studies further support a foundation to develop molecular and genetic tools for dermatophyte and dimorphic human fungal pathogens.