ABSTRACT
In fungitalic>, sexual reproduction provides the scope for genetic diversity and purging deleterious genes. Within homothallics, different types are recognized. For example, the complementary idiomorphs required to ensure successful mating coexist within the same genome and are fused into one MAT locus on the same ‘sex’ chromosome in the ascomycote Cochliobolus spp. But they are not linked and located at different positions within the same genome in Aspergillus nidulans. In the tetrapolar mating system too, the homeodomain and pheromone/pheromone receptor locitalic> are not linked. Hence, their complementary mating types must differ at both locitalic> to ensure successful mating. The identified sex determining genes are A and B in most basidiomycotes but MATa and MATɑ in Saccharomyces cerevisiae. A few adaptive strategies adopted by parasites are explained in the basidiomycotes Cryptococcus neoformans and Sporisorium reiliarum, in which fusion occurs between mating types arising from the same homothallic. In ascomycetous parasites too, similar homothallic fusion occurs in Fusarium oxysporum, Candida albicans and others. In fungitalic>, the progenies do not inherit ‘paternal’ mitochondria. However, when they are inherited as in S. cerevisiae, the uniparental inheritance is soon reestablished.
