Sexuality Control and Sex Evolution in Fungi

Fungi have been used as robust and genetic models to study the mechanisms of eukaryotic sexuality controls, which have revealed the common mechanisms including ploidy changes, the formation of gametes via meiosis, recognition of mating partner and cell-cell fusion to form zygotes. Sexuality in fungi is controlled by mating-type loci. There are three modes of sexual reproduction in fungi, heterothallism (very much like two sex mating system in other eukaryotes), homothallism and pseudohomothallism. Different from other eukaryotic organisms, some fungal species like yeasts can perform mating-type switching. Fungal haploids with opposite mating-type locus can recognize each other by a compatible pheromone-receptor system. The sexual process and fruiting-body development are regulated by the following G-protein coupled receptor pathways. The initiation of fungal sex is also determined by multiple intracellular as well as extracellular factors. The disparity has been frequently observed in different fungal lineages in terms of the association between fungal sexual mode evolution and speciation. Future studies to unveil the environmental cues in initiating fungal sexuality will not only facilitate the understanding of myriad forms of fungal sex but also benefit the effective use of economic fungi by artificial cultivation of fungal fruiting-bodies.