The expansion of the sex locus is also implicated by observations in the other Mucorales species, which Navitoclax nmr include an expansion of the sex locus to include the tptA and

rnhA gene promoters in M. circinelloides, a transposition of the arbA gene into the sex locus in R. oryzae and S. megalocarpus (or loss from other species/loci) and diversification of neighbouring rnhA genes and a gene encoding glutathione oxidoreductase in S. megalocarpus.[27] The sex locus of the Mucorales provides novel insights to understand sex chromosome evolution, in addition to the MAT loci of the dikarya, which provide insights on partner recognition and mating regulation. Furthermore, both humans and Mucoralean fungi utilise HMG proteins as key transcription factors for sex determination, and thus HMG proteins may be ancestral sex determinants. Mating between two different mating types produces progeny with a 1:1 segregation of both mating types. However, a significant mating type skew is found in pathogenic Mucor species. M. amphibiorum is a causal agent of ulcerative mycosis on platypuses in northern Tasmania in Australia. The

isolates from this area mainly represent (+) mating types and, in a toad mucormycosis model, the (+) mating types were more virulent than the (−) mating types.[36] The study found that the (+) mating types of M. amphibiorum caused more severe diseases in toads by producing spherules more BMN 673 rapidly than the (−) mating types. A similar mating type bias was observed in a plant pathogenic Mucorales. M. piriformis causes mucor rot in pear fruit and a study revealed that (+) mating type predominates over

(−) mating type in infected plants in Oregon pear orchards.[37] Interestingly, the (+) mating types produced larger lesions than the (−) mating types although both mating types can cause infections under laboratory conditions. In M. circinelloides, (−) mating type isolates tend to produce more virulent, larger spores than (+) mating type isolates, which produce less virulent, smaller spores; however, a subsequent finding suggested that the sexM gene in (−) mating type is not solely responsible for the spore DAPT molecular weight size difference in that sexMΔ mutants still produce larger spores.[24] Spore size could be controlled by SexP, by other genetic loci, or by other genetic loci acting in concert with SexM as a quantitative trait. Analogy is found in the human pathogenic basidiomycete Cryptococcus neoformans, in which the α mating type predominates in clinical and environmental samples (reviewed in [35]). In C. neoformans, unisexual reproduction explains this mating type bias[38, 39]; however, unisexual reproduction has not been described in the pathogenic Mucorales and currently there is no apparent explanation for the mating type bias in pathogenic Mucor species.