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Molecular Mechanisms of Sexual Reproduction in the Order Cystofilobasidiales
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Resumo(s)
In fungi, mating-type is defined by the MAT loci. Heterothallic fungi can only reproduce sexually through mating with a second strain of distinct mating-type, which carry different alleles at the MAT loci. On the contrary, homothallic fungi complete their sexual life cycle without the need for a compatible partner. In Basidiomycota, MAT loci encode pheromones, pheromone receptors and the homeodomain transcription factors HD1 and HD2, which normally function as HD1/HD2 heterodimers and are all usually required for sexual reproduction.
This study aimed to shed some light on the sexual reproduction systems within the order Cystofilobasidiales, a lineage in the Basidiomycota with an unusually high proportion of homothallic species. To this end, two lines of study were conducted.
Firstly, the genes contained in the MAT loci from species of the Cystofilobasidium genus were examined from a phylogenetic standpoint, revealing novel findings pertaining in particular to the species Cystofilobasidium ferigula and Cystofilobasidium macerans. The findings concerning the latter species suggest that it may be in transition between heterothallism and homothallism.
Secondly, the interaction between HD1 and HD2 proteins, normally indispensable for sexual reproduction in heterothallic species, was studied in two homothallic species: Phaffia rhodozyma, continuing the study initiated by David-Palma et al, 2016; and Cystofilobasidium capitatum, in comparison to a heterothallic species of the same genus, C. ferigula. For C. capitatum, the heterologous expression of its HD locus in a P. rhodozyma cognate deletion mutant was able to restore sporulation, indicating that these proteins are functional and play a role in homothallism. However, the results from the Yeast Two-Hybrid assay with C. capitatum proteins did not reveal a strong interaction between HD1 and HD2 in this species, but rather a clear homodimerization of HD2, leaving plenty of room for further investigation of the molecular functions of HD proteins in C. capitatum.
Descrição
Palavras-chave
Cystofilobasidiales MAT loci Homothallism Homeodomain Sexual Reproduction