Project description:Goal: We employed RNA-seq to identify targets of regulation of five Candida albicans transcription regulators (Try4, Zfu2 and Zcf8). These regulators were identifyed through a genetic screen in a gnotobiotic mouse model of Candida albicans gut colonization. Results: We found that the five regulators comprise a complex transcriptional network (>500 targets of regulation) that partitions in two sub-networks. One sub-network is formed by Rtg1 and Rtg3. The other comprises the regulators Try4, Zfu2 and Zcf8.
Project description:All but a few eukaryotes die without oxygen and respond dynamically to changes in the level of oxygen available to them. One ancient oxygen-requiring biochemical pathway in eukaryotes is the pathway for the biosynthesis of sterols, leading to cholesterol in animals and ergosterol in fungi. Mutations in this pathway are a frequent cause of azole drug resistance in pathogenic fungi. The regulatory mechanism for the sterol pathway is also widely conserved between animals and fungi and is centred on a transcription activator, SREBP, that forms part of a sterol-sensing complex. However, in one group of yeasts – the Saccharomycotina, which includes the major pathogen Candida albicans – control of the sterol pathway has been taken over by an unrelated regulatory protein, Upc2. We show here by analysis of the yeast Yarrowia lipolytica that the evolutionary switch from SREBP to Upc2 was a two-step process in which Upc2 appeared in an ancestor of Saccharomycotina, and SREBP subsequently degenerated and lost its sterol-regulatory function while retaining an ancient role in filamentation.
Project description:Rme1, a conserved transcription factor among members of the ascomycete lineage, regulates meiosis and pseudohyphal growth in baker’s yeast. The genome of the meiosis-defective fungal pathogen Candida albicans encodes a Rme1 homolog, which we previously mapped within a transcriptional circuitry that controls hyphal growth. To delineate a possible role of Rme1 in C. albicans morphogenesis, we combined genome-wide expression and location analyses of Rme1. Strikingly, Rme1 bound upstream and activated the expression of markers of chlamydosporulation, a process leading to formation of large, spherical, thick-walled cells during nutrient starvation. RME1 deletion abolished chlamydosporulation in three chlamydospore-forming Candida species, whereas its overexpression bypassed the requirement for chlamydosporulation cues and regulators, indicating that Rme1 is central to chlamydospore development. Moreover, RME1 expression levels correlated with chlamydosporulation efficiency among clinical isolates, further highlighting Rme1 importance in this process. Interestingly, RME1 displayed a biphasic pattern of expression, with a first phase independent of Rme1 function and dependent on chlamydospore-inducing cues, and a second phase depending upon Rme1 function and independent of chlamydospore-inducing cues. We suggest that Rme1 function spans from the regulation of meiosis in sexual yeasts to the control of an epigenetic switch necessary for asexual spore formation in meiosis-defective Candida species.
Project description:Rme1, a conserved transcription factor among members of the ascomycete lineage, regulates meiosis and pseudohyphal growth in baker’s yeast. The genome of the meiosis-defective fungal pathogen Candida albicans encodes a Rme1 homolog, which we previously mapped within a transcriptional circuitry that controls hyphal growth. To delineate a possible role of Rme1 in C. albicans morphogenesis, we combined genome-wide expression and location analyses of Rme1. Strikingly, Rme1 bound upstream and activated the expression of markers of chlamydosporulation, a process leading to formation of large, spherical, thick-walled cells during nutrient starvation. RME1 deletion abolished chlamydosporulation in three chlamydospore-forming Candida species, whereas its overexpression bypassed the requirement for chlamydosporulation cues and regulators, indicating that Rme1 is central to chlamydospore development. Moreover, RME1 expression levels correlated with chlamydosporulation efficiency among clinical isolates, further highlighting Rme1 importance in this process. Interestingly, RME1 displayed a biphasic pattern of expression, with a first phase independent of Rme1 function and dependent on chlamydospore-inducing cues, and a second phase depending upon Rme1 function and independent of chlamydospore-inducing cues. We suggest that Rme1 function spans from the regulation of meiosis in sexual yeasts to the control of an epigenetic switch necessary for asexual spore formation in meiosis-defective Candida species.