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Telomeric ORFs (TLOs) in pathogenic Candida spp. encode Mediator subunits that regulate the transcription of distinct subsets of genes

ABSTRACT: Analysis of the role of the Candida dubliniensis Telomeric (TLO) genes and MED3, encoding subunits of Mediator, in regulating transcription The transcriptional response of a Candida dubliniensis TLO1/TLO2 double (null) mutant was analysed. Reintegrant strains harboring TLO1 or TLO2 were compared to this null mutant to elucidate the individual role of each ORF. The role of MED3 was compared also.

ORGANISM(S): Candida dubliniensis

PROVIDER: GSE59113 | GEO | 2014/07/11

SECONDARY ACCESSION(S): PRJNA254947

REPOSITORIES: GEO

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Project description:The TLO genes are a family of telomere-associated ORFs in the fungal pathogens Candida albicans and C. dubliniensis that encode a subunit of the Mediator complex with homology to Med2. The more virulent pathogen C. albicans has 15 copies of the gene whereas the less pathogenic species C. dubliniensis has only two (CdTLO1 and CdTLO2). In this study we used C. dubliniensis as a model to investigate the role of TLO genes in regulating virulence and also to determine whether TLO paralogs have evolved to regulate distinct functions. A C. dubliniensis tlo1Δ/tlo2Δ mutant is unable to form true hyphae, has longer doubling times in galactose broth, is more susceptible to oxidative stress and forms increased levels of biofilm. Transcript profiling of the tlo1Δ/tlo2Δ mutant revealed increased expression of starvation responses in rich medium and retarded expression of hypha-induced transcripts in serum. ChIP studies indicated that Tlo1 binds to many ORFs including genes that exhibit high and low expression levels under the conditions analyzed. The altered expression of these genes in the tlo1Δ/tlo2Δ null mutant indicates roles for Tlo proteins in transcriptional activation and repression. Complementation of the tlo1Δ/tlo2Δ mutant with TLO1, but not TLO2, restored wild-type filamentous growth, whereas only TLO2 fully suppressed biofilm growth. Complementation with TLO1 also had a greater effect on doubling times in galactose broth. The different abilities of TLO1 and TLO2 to restore wild-type functions was supported by transcript profiling studies that showed that only TLO1 restored expression of hypha-specific genes (UME6, SOD5) and galactose utilisation genes (GAL1 and GAL10), whereas TLO2 restored repression of starvation-induced gene transcription. Thus, Tlo/Med2 paralogs encoding Mediator subunits regulate different virulence properties in Candida spp. and their expansion may account for the increased adaptability of C. albicans relative to other Candida species.

Project description:Candida albicans and Candida dubliniensis are closely related species displaying differences in virulence and genome content, therefore providing potential opportunities to identify novel C. albicans virulence genes. C. albicans gene arrays were used for comparative analysis of global gene expression in the two species in reconstituted human oral epithelium (RHE). C. albicans (SC5314) showed upregulation of hypha-specific and virulence genes within 30 min postinoculation, coinciding with rapid induction of filamentation and increased RHE damage. C. dubliniensis (CD36) showed no detectable upregulation of hypha-specific genes, grew as yeast, and caused limited RHE damage. Several genes absent or highly divergent in C. dubliniensis were upregulated in C. albicans. One such gene, SFL2 (orf19.3969), encoding a putative heat shock factor, was deleted in C. albicans. ÎÎsfl2 cells failed to filament under a range of hypha-inducing conditions and exhibited greatly reduced RHE damage, reversed by reintroduction of SFL2 into the ÎÎsfl2 strain. Moreover, SFL2 overexpression in C. albicans triggered hyphal morphogenesis. Although SFL2 deletion had no apparent effect on host survival in the murine model of systemic infection, ÎÎsfl2 strain-infected kidney tissues contained only yeast cells. These results suggest a role for SFL2 in morphogenesis and an indirect role in C. albicans pathogenesis in epithelial tissues. Global gene expression in Candida albicans SC5314 or Candida dubliniensis CD36 on reconstituted human oral epithelium (RHE) 90 min postinoculation. Gene expression on RHE was compared to gene expression on polycarbonate filter (PCF; used as RHE support matrix) 90 min postinoculation. Performed in two biological replicates with reciprocal dye swaps for each biological replicate. Gene expression of Candida cells on RHE was normalized to gene expression in reference control (PCF); log2 ratios were calculated by dividing spot intensity of experimental by that of the reference control.

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Telomeric ORFs (TLOs) in pathogenic Candida spp. encode Mediator subunits that regulate the transcription of distinct subsets of genes

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