title: Identification of the sex genes in an early diverged fungus.
abstract: Sex determination in fungi is controlled by a small, specialized region of the genome in contrast to the large sex-specific chromosomes of animals and some plants. Different gene combinations reside at these mating-type (MAT) loci and confer sexual identity; invariably they encode homeodomain, alpha-box, or high mobility group (HMG)-domain transcription factors. So far, MAT loci have been characterized from a single monophyletic clade of fungi, the Dikarya (the ascomycetes and basidiomycetes), and the ancestral state and evolutionary history of these loci have remained a mystery. Mating in the basal members of the kingdom has been less well studied, and even their precise taxonomic inter-relationships are still obscure. Here we apply bioinformatic and genetic mapping to identify the sex-determining (sex) region in Phycomyces blakesleeanus (Zygomycota), which represents an early branch within the fungi. Each sex allele contains a single gene that encodes an HMG-domain protein, implicating the HMG-domain proteins as an earlier form of fungal MAT loci. Additionally, one allele also contains a copy of a unique, chromosome-specific repetitive element, suggesting a generalized mechanism for the earliest steps in the evolution of sex determination and sex chromosome structure in eukaryotes.
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Idnurm
authors.forename: Felicia J
authors.initials: FJ
authors.lastname: Walton
authors.forename: Anna
authors.initials: A
authors.lastname: Floyd
authors.forename: Joseph
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D015825:Chromosomes, Fungal / Q000235:genetics; D019295:Computational Biology; D005298:Fertility / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics; D005658:Fungi / Q000145:classification / Q000235:genetics*; D005800:Genes, Fungal / Q000235:genetics*; D049770:Genes, Mating Type, Fungal / Q000235:genetics; D024742:HMG-Box Domains; D006579:Heterozygote; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011995:Recombination, Genetic / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012723:Sex; D019849:Sex Determination Processes
chemical_list: D005656:Fungal Proteins; D006609:High Mobility Group Proteins