Project description:Cryptococcus neoformans (Cn) is an opportunistic fungal microorganism that causes life-threatening meningoencephalitis. Calorie restriction is an intervention that extends the lifespan of Cn. The mating types of Cn have striking differences in prevalence in both environmental and clinical settings. This is hypothesized to be due to differences in stress responses between mating types. Using RNAseq, we investigated how the two mating types respond to the stress of starvation during calorie restriction.
Project description:It has been proposed that the ancestral fungus was mating competent and homothallic. However, many mating competent fungi were initially classified as asexual because their mating capacity was hidden behind layers of regulation. For efficient in vitro mating, the essentially obligate diploid ascomycete pathogen C. albicans has to homozygose its mating type locus from MTLa/α to MTLa/a or MTLα/α, and then undergo an environmentally controlled epigenetic switch to the mating competent opaque form. These requirements greatly reduce the potential for C. albicans mating. Deletion of the YciI domain gene OFR1 bypasses the need for C. albicans cells to homozygose the mating type locus prior to switching to the opaque form and mating, and allows homothallic mating of MTL heterozygous strains. This bypass is carbon source dependent and does not occur when cells are grown on glucose. Transcriptional profiling of ofr1 mutant cells shows that in addition to regulating cell type and mating circuitry, Ofr1 is needed for proper regulation of histone and chitin biosynthesis gene expression. It appears that OFR1 is a key regulator in C. albicans, and functions in part to maintain the cryptic mating phenotype of the pathogen. Distruption of OFR1 gene which encodes a Yci1 related domain in Candida ablicans (MTLa/α) is shown to have white-opaque switching related and mating related gene expression. The expression of histone genes are also positively regulated in some conditions.
Project description:Sexual reproduction facilitates infection by the production of both a lineage advantage and infectious sexual spores in the ubiquitous human fungal pathogen Cryptococcus deneoformans. However, the regulatory determinants specific for initiating mating remain poorly understood. Here, we identified a velvet family regulator, Cva1, that strongly promotes sexual reproduction in C. deneoformans. This regulation was determined to be specific, based on a comprehensive phenotypic analysis of cva1 under 25 distinct in vitro and in vivo growth conditions. We further revealed that Cva1 plays a critical role in the initiation of early mating events, especially sexual cell-cell fusion, but is not important for the late sexual development stages or meiosis. Thus, Cva1 specifically contributes to mating activation. Importantly, a novel mating-responsive surface protein, Cfs1, serves as the key target of Cva1 during mating, since its absence nearly blocks cell-cell fusion in C. deneoformans and its sister species C. neoformans. Together, our findings provide insight into how C. deneoformans ensures regulatory specificity of mating.
Project description:We examined the mating response of W303 bar1delta a-type cells to six alpha-factor concentrations (0.06, 0.2, 0.6, 6, 60 and 600 nM). In each alpha factor concentration between five to seven time points were collected. The time points in all experiments (except for concentration 600 nM were time point 15 min was omitted) were 5, 15, 30, 60, and 90 min. In some of the concentrations also time points 120 and 150 min were considered. The expression of cells before and after addition of alpha-factor were compared using S. cerevisiae cDNA microarrays, in all experiments the same sample before adding alpha factor was used as a control. Keywords: yeast mating response, comparison among alpha factor concentrations