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Telomeric ORFs (TLOs) in Candida spp. Encode mediator subunits that regulate distinct virulence traits.

Haran J, Boyle H, Hokamp K, Yeomans T, Liu Z, Church M, Fleming AB, Anderson MZ, Berman J, Myers LC, Sullivan DJ, Moran GP - PLoS Genet. (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Division of Oral Biosciences, Dublin Dental University Hospital, University of Dublin, Trinity College Dublin, Dublin, Ireland.

ABSTRACT
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 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.

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The relationship between Tlo1 binding and gene expression.(A) A plot of Tlo1 enrichment scores for the 367 most highly enriched genes versus the expression levels of those genes in YEPD broth (extracted from microarray data). The categories of highly expressed and repressed genes are color-coded; TCA = Tricarboxylic acid cycle; Sulfur AA = sulphur amino acid biosynthesis; N scavenging = Nitrogen scavenging; NAG = GlcNac metabolism; GPI = glycophosphatidylinositol anchor). (B) Analysis of the expression of Tlo1-enriched groups of genes in the wild type in the tlo1Δ/tlo2Δ (tloΔΔ) mutant indicated that the highly expressed, highly enriched genes exhibited reduced expression whereas the poorly expressed and repressed genes exhibited increased expression in the tlo1Δ/tlo2Δ (tloΔΔ) mutant. The change in expression in these groups, with the exception of the genes involved on translation, was significant (ANOVA, P<0.05).
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pgen-1004658-g009: The relationship between Tlo1 binding and gene expression.(A) A plot of Tlo1 enrichment scores for the 367 most highly enriched genes versus the expression levels of those genes in YEPD broth (extracted from microarray data). The categories of highly expressed and repressed genes are color-coded; TCA = Tricarboxylic acid cycle; Sulfur AA = sulphur amino acid biosynthesis; N scavenging = Nitrogen scavenging; NAG = GlcNac metabolism; GPI = glycophosphatidylinositol anchor). (B) Analysis of the expression of Tlo1-enriched groups of genes in the wild type in the tlo1Δ/tlo2Δ (tloΔΔ) mutant indicated that the highly expressed, highly enriched genes exhibited reduced expression whereas the poorly expressed and repressed genes exhibited increased expression in the tlo1Δ/tlo2Δ (tloΔΔ) mutant. The change in expression in these groups, with the exception of the genes involved on translation, was significant (ANOVA, P<0.05).

Mentions: Using fluorescence intensity data extracted from our gene expression microarrays, we compared the expression levels of the Tlo1-associated ORFs relative to non-Tlo1 associated ORFs. Tlo1-associated ORFs were found to exhibit higher expression levels (average 1.8-fold) in YEPD compared to those genes that are not occupied (Figure S9C). However, a plot of enrichment score versus expression level did not identify a direct correlation between Tlo1 enrichment and expression. Importantly, the most highly enriched genes (n = 367; Ringo peak score 0.9) covered a broad spectrum of expression levels, including genes expressed at high and low levels in YEPD (Figure 9A). We analysed the GO terms associated with these Tlo1-enriched genes and identified significant numbers of highly expressed genes associated with the GO categories glycolysis (n = 7; P = 0.003) and the TCA cycle (n = 7; P = 0.048)(Figure 9A). Manual inspection of the gene list also identified highly expressed genes involved in translation (n = 5) and sulphur amino acid metabolism (n = 4). Tlo1-enriched genes that are poorly expressed in YEPD were associated with the GO categories glyoxylate cycle (n = 3; P = 0.09), GlcNac catabolic process (n = 6, P = 0.094), amino acid catabolic process (n = 10; P = 0.018) and hexose transport (n = 9; P = 0.057). Manual inspection also identified poorly expressed genes encoding nitrogen scavenging transporters (e.g. FRP6, MEP21, MEP22, DAL1, UGA6) and genes involved in gluconeogenesis (PCK1 and FBP1). Many YEPD repressed, hypha-specific genes were also enriched including EED1, RBT1, HWP1, HWP2 and IHD1.


Telomeric ORFs (TLOs) in Candida spp. Encode mediator subunits that regulate distinct virulence traits.

Haran J, Boyle H, Hokamp K, Yeomans T, Liu Z, Church M, Fleming AB, Anderson MZ, Berman J, Myers LC, Sullivan DJ, Moran GP - PLoS Genet. (2014)

The relationship between Tlo1 binding and gene expression.(A) A plot of Tlo1 enrichment scores for the 367 most highly enriched genes versus the expression levels of those genes in YEPD broth (extracted from microarray data). The categories of highly expressed and repressed genes are color-coded; TCA = Tricarboxylic acid cycle; Sulfur AA = sulphur amino acid biosynthesis; N scavenging = Nitrogen scavenging; NAG = GlcNac metabolism; GPI = glycophosphatidylinositol anchor). (B) Analysis of the expression of Tlo1-enriched groups of genes in the wild type in the tlo1Δ/tlo2Δ (tloΔΔ) mutant indicated that the highly expressed, highly enriched genes exhibited reduced expression whereas the poorly expressed and repressed genes exhibited increased expression in the tlo1Δ/tlo2Δ (tloΔΔ) mutant. The change in expression in these groups, with the exception of the genes involved on translation, was significant (ANOVA, P<0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214616&req=5

pgen-1004658-g009: The relationship between Tlo1 binding and gene expression.(A) A plot of Tlo1 enrichment scores for the 367 most highly enriched genes versus the expression levels of those genes in YEPD broth (extracted from microarray data). The categories of highly expressed and repressed genes are color-coded; TCA = Tricarboxylic acid cycle; Sulfur AA = sulphur amino acid biosynthesis; N scavenging = Nitrogen scavenging; NAG = GlcNac metabolism; GPI = glycophosphatidylinositol anchor). (B) Analysis of the expression of Tlo1-enriched groups of genes in the wild type in the tlo1Δ/tlo2Δ (tloΔΔ) mutant indicated that the highly expressed, highly enriched genes exhibited reduced expression whereas the poorly expressed and repressed genes exhibited increased expression in the tlo1Δ/tlo2Δ (tloΔΔ) mutant. The change in expression in these groups, with the exception of the genes involved on translation, was significant (ANOVA, P<0.05).
Mentions: Using fluorescence intensity data extracted from our gene expression microarrays, we compared the expression levels of the Tlo1-associated ORFs relative to non-Tlo1 associated ORFs. Tlo1-associated ORFs were found to exhibit higher expression levels (average 1.8-fold) in YEPD compared to those genes that are not occupied (Figure S9C). However, a plot of enrichment score versus expression level did not identify a direct correlation between Tlo1 enrichment and expression. Importantly, the most highly enriched genes (n = 367; Ringo peak score 0.9) covered a broad spectrum of expression levels, including genes expressed at high and low levels in YEPD (Figure 9A). We analysed the GO terms associated with these Tlo1-enriched genes and identified significant numbers of highly expressed genes associated with the GO categories glycolysis (n = 7; P = 0.003) and the TCA cycle (n = 7; P = 0.048)(Figure 9A). Manual inspection of the gene list also identified highly expressed genes involved in translation (n = 5) and sulphur amino acid metabolism (n = 4). Tlo1-enriched genes that are poorly expressed in YEPD were associated with the GO categories glyoxylate cycle (n = 3; P = 0.09), GlcNac catabolic process (n = 6, P = 0.094), amino acid catabolic process (n = 10; P = 0.018) and hexose transport (n = 9; P = 0.057). Manual inspection also identified poorly expressed genes encoding nitrogen scavenging transporters (e.g. FRP6, MEP21, MEP22, DAL1, UGA6) and genes involved in gluconeogenesis (PCK1 and FBP1). Many YEPD repressed, hypha-specific genes were also enriched including EED1, RBT1, HWP1, HWP2 and IHD1.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Division of Oral Biosciences, Dublin Dental University Hospital, University of Dublin, Trinity College Dublin, Dublin, Ireland.

ABSTRACT
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 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.

Show MeSH
Related in: MedlinePlus