RNA-sequencing reveals allelic expression imbalance in the diploid pathogen Candida albicans
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ABSTRACT: The diploid fungal pathogen Candida albicans is a highly heterozygous organism, with numerous non-synonymous substitutions often seen within two alleles. RNA-sequencing of the wild-type strain SC5314 has revealed 233 genes with significant levels of allelic expression imbalance. Overall percentage protein identity comparisons were significantly lower in these differentially expressed alleles. This suggests that two different, perhaps functionally divergent, proteins are being expressed at significantly different quantities by the two alleles of a single gene. Previously, gene expression levels have been correlated with structural factors such as GC content, ORF length and codon usage. Here, these factors were first correlated with overall gene expression data to decipher the relationship they have with gene expression in Candida albicans. These relationships were then used to assess the contribution of these factors to allelic expression imbalance. GC content and codon usage did not differ significantly in differentially expressed alleles whereas ORF length was found to be significantly lower in the allele with lowest expression. This surprising result goes against the overall trend observed between length and gene expression. Differences in GC content and ORF length between alleles correlated strongly with percentage protein identity, suggesting an indirect link between these factors and allelic expression imbalance. One sample (SC5314: wild-type strain) assessed in triplicate and compared to the reference diploid genome
Project description:RNA-seq analysis of an in vivo murine model of vulvovaginal candidiasis Murine vaginas were infected with Candida albicans and harvested for RNA-seq analysis 3 days post-infection
Project description:We report that a transcriptional regulator that originated in the lineage that gave rise to multiple host-associated Candida species is a key component of the circuitry that governs the C. albicans cell surface composition. Specifically, we show that the transcription regulator ZCF21 controls the expression of genes encoding multiple cell surface proteins and cell wall modifying enzymes. Transcriptome (RNA-seq) analysis of 2 Candida albicans strains (reference strain and zcf21 deletion mutant) grown under 4 culture conditions (YPD broth at 30°C for 24h; YPD broth at 30°C in the presence of 15 mM caffeine for 24h; Todd-Hewitt agar at 37°C for 24h; Todd-Hewitt agar at 37°C for 24h in the presence of 5 mM caffeine).
Project description:The dataset contains ChIP-Seq data of the Set3 and Hos2 proteins in Candida albicans, assayed in two morphological phases (yeast and hypha). The Set3 and Hos2 proteins in the respective strains carry 9myc epitopes and ChIP was performed with an anti-myc antibody. Included samples are the following: 1 input and 1 ChIP sample of an untagged wild type strain as negative control assayed in the yeast phase, 1 input and 3 ChIP biological replicates of the Set3-9myc strain in the yeast phase, 1 input and 2 ChIP biological replicates of the Set3-9myc strain in the hypha phase, 1 input and 2 ChIP biological replicates of the Hos2-9myc strain in the yeast phase, 1 input and 2 ChIP biological replicates of the Hos2-9myc strain in the hypha phase, 1 input and 3 ChIP biological replicates of Set3-9myc in a set1delta/delta background in the yeast phase. ChIP-Seq was performed of Candida albicans strains in two morphological phases (yeast and hypha). Yeast-phase cells were grown to the exponential phase in YPD at 30C. Hyphal differentiation was induced by resuspending the cells in YPD+20% Fetal Calf Serum and a shift of the growth temperature to 37C. Induction was performed for 30 minutes. Cells were crosslinked with 1% formaldehyde for 15 minutes at room temperature.
Project description:Biofilm formation on medically implanted devices by Candida albicans poses a significant clinical challenge. Here we compared biofilm-associated gene expression in two clinical C. albicans isolates, SC5314 and WO-1, to identify shared gene regulatory responses that may be functionally relevant. Among the 50 genes most highly expressed in biofilms relative to planktonic (suspension-grown) cells, we were able to recover insertion mutations in 25 genes. We observed that 20 of the 25 mutants have altered biofilm-related properties, including cell-substrate adherence, cell-cell signaling, and azole susceptibility. We focused on the most highly up-regulated gene in biofilms, RHR2, which specifies the glycerol biosynthetic enzyme glycerol-3-phosphate phosphatase. Glycerol is 5-fold more abundant in biofilm cells than planktonic cells, and an rhr2D/D strain accumulates 2-fold less biofilm glycerol than the wild type. Under in vitro growth conditions, the rhr2D/D mutant has reduced biofilm biomass and reduced adherence to silicone. The rhr2D/D mutant is severely defective in biofilm formation in vivo, in a rat catheter infection model. Expression profiling of the rhr2D/D mutant indicates that it has reduced expression of cell surface adhesin genes ALS1, ALS3, and HWP1, as well as a large fraction of all other biofilm up-regulated genes. Reduced adhesin expression is the cause of the rhr2D/D mutant biofilm defect, because overexpression of ALS1, ALS3, or HWP1 restores biofilm formation ability to the mutant in vitro and in vivo. Our findings indicate that internal glycerol has a regulatory role in biofilm gene expression, and that adhesin genes are among the main functional Rhr2-regulated genes. Gene expression profiles, in duplicate; (1) for biofilm vs. planktonic growth conditions for the two wild-type clinical isolates of Candida albicans (SC5314 and WO1-white/WO1-opaque), and (2) for rhr2M-NM-^T/M-NM-^T mutant and complemented strain, via RNA-deep sequencing using Illumina GA2 and HiSeq2000 platforms, respectively
Project description:Recent works show that protein mistranslation is widespread in nature and that both single cell or multicellular organisms can take advantage of it, by regulating its levels, under specific physiological and environmental conditions. In C. albicans, it leads to increased morphological and physiological phenotypic diversity of high adaptive potential, but the scope of such protein mistranslation is poorly understood due to technical difficulties in detecting and quantifying amino acid misincorporation events in complex proteomic samples. The phenomenon of mistranslation has been extensively studied in the leucine CUG codon, which has been reassigned to either serine or alanine, or ambiguously assigned to serine and leucine in several fungal species of the so called CTG clade. Serine-to-leucine (Ser→Leu) ambiguous decoding has been observed in Ascoidea asiatica, Candida maltosa, C. albicans and more recently, in the halotolerant yeast Debaryomyces hansenii. In C. albicans, CUG translation is facilitated by a hybrid tRNA(CAG)Ser that contains identity elements for both seryl-tRNA synthetase (SerRS) and leucyl-tRNA synthetase (LeuRS). Under normal physiological conditions the tRNA(CAG)Ser is mainly aminoacylated with Ser by the SerRS (appx 97%). We have developed and optimized mass spectrometry and bioinformatics pipelines capable of identifying low-level amino acid misincorporation events at the proteome level and determine codons error frequencies. We have also analysed the proteomic profile of an engineered C. albicans strain that exhibits high level of leucine misincorporation at protein CUG sites.
Project description:Though sequence differences between alleles are often limited to a few polymorphisms, these differences can cause large and widespread allelic variation at the expression level. Such allele-specific expression (ASE) has been extensively explored at the level of transcription but not translation. Here we measured ASE in the diploid yeast Candida albicans at both the transcriptional and translational levels using RNA-seq and ribosome profiling, respectively. Since C. albicans is an obligate diploid, our analysis isolates ASE arising from cis elements in a natural, non-hybrid organism, where allelic effects reflect evolutionary forces. Importantly, we find that ASE arising from translation is of a similar magnitude as transcriptional ASE, both in terms of the number of genes affected and the magnitude of the bias. We further observe coordination between ASE at the levels of transcription and translation for single genes. Specifically, reinforcing relationshipsM-bM-^@M-^Twhere transcription and translation favor the same alleleM-bM-^@M-^Tare more frequent than expected by chance, consistent with selective pressure tuning ASE at multiple regulatory steps. Finally, we parameterize alleles based on a range of properties and find that SNP location and predicted mRNA-structure stability are associated with translational ASE in cis. Since this analysis probes more than 4,000 allelic pairs spanning a broad range of variations, our data provide a genome-wide view into the relative impacts of cis elements that regulate translation. Two biological replicates of WT Candida albicans ribosome profiling and RNA-seq
Project description:In silico spectral library prediction of all possible peptides from whole organisms has a great potential for improving proteome profiling by data-independent acquisition and extending its scope of application. In combination with other recent improvements in the field, including sample preparation, peptide separation and data analysis, we aimed to uncover the full potential of such an advanced DIA strategy by isolation window optimization. The results demonstrate that the combination of high-quality in silico libraries, reproducible and high-resolution peptide separation using micro-pillar array columns as well as neural network supported data analysis enables the use of long MS scan cycles without impairing the quantification performance.
Project description:Drug susceptible clinical isolates of Candida albicans frequently become highly tolerant to drugs during chemotherapy, with dreadful consequences on patient health. We used RNA sequencing (RNA-seq) to analyze the transcriptomes of a CDR (Candida Drug Resistance) strain and its isogenic drug sensitive counterpart. RNA-seq unveiled differential expression of 228 genes including a) genes previously identified as involved in CDR, b) genes not previously associated to the CDR phenotype, and c) novel transcripts whose function as a gene is uncharacterized. In particular, we show for the first time that CDR acquisition is correlated with an overexpression of the transcription factor encoding gene CZF1. CZF1 null mutants were sensitive to many drugs, independently of known multidrug resistance mechanisms. We show that CZF1 acts as a repressor of M-NM-2-glucan synthesis, thus negatively regulating cell wall integrity. Finally, our RNA-seq data allowed us to identify a new transcribed region, upstream of the TAC1 gene, which encodes the major CDR transcriptional regulator. Our results open new perspectives to the role of Czf1 and to our understanding of the transcriptional and post-transcriptional mechanisms that lead to the acquisition of drug resistance in C. albicans, with potential future improvements of therapeutic strategies. RNA sequencing was performed on 2 Candida albicans strains (Gu4 and Gu5). For each strain, we sequenced 2 biological replicates.
Project description:Sfl1p and Sfl2p are two homologous heat shock factor-type transcriptional regulators that antagonistically control morphogenesis in Candida albicans, while being required for full pathogenesis and virulence. To understand how Sfl1p and Sfl2p exert their function, we combined genome-wide location and expression analyses to reveal their transcriptional targets in vivo together with the associated changes of the C. albicans transcriptome. We show that Sfl1p and Sfl2p bind to the promoter of at least 113 common targets through divergent binding motifs and modulate directly the expression of key transcriptional regulators of C. albicans morphogenesis and/or virulence. Surprisingly, we found that Sfl2p additionally binds to the promoter of 75 specific targets, including a high proportion of hyphal-specific genes (HSGs; HWP1, HYR1, ECE1, others), revealing a direct link between Sfl2p and hyphal development. Data mining pointed to a regulatory network in which Sfl1p and Sfl2p act as both transcriptional activators and repressors. Sfl1p directly represses the expression of positive regulators of hyphal growth (BRG1, UME6, TEC1, SFL2), while upregulating both yeast form-associated genes (RME1, RHD1,YWP1) and repressors of morphogenesis (SSN6, NRG1). On the other hand, Sfl2p directly upregulates HSGs and activators of hyphal growth (UME6, TEC1), while downregulating yeast form-associated genes and repressors of morphogenesis (NRG1, RFG1, SFL1). Using genetic interaction analyses, we provide further evidences that Sfl1p and Sfl2p antagonistically control C. albicans morphogenesis through direct modulation of the expression of important regulators of hyphal growth. Bioinformatic analyses suggest that binding of Sfl1p and Sfl2p to their targets occurs with the co-binding of Efg1p and/or Ndt80p. Indeed, we show that Sfl1p and Sfl2p targets are bound by Efg1p and that both Sfl1p and Sfl2p associate in vivo with Efg1p. Taken together, our data suggest that Sfl1p and Sfl2p act as central M-bM-^@M-^\switch on/offM-bM-^@M-^] proteins to coordinate the regulation of C. albicans morphogenesis. ChIP was performed in 2 independently grown C. albicans sfl1 or sfl2 homozygous mutant strains expressing (sfl1-CaEXP-SFL1-HA or sfl2-CaEXP-SFL2-HA, respectively) or not (sfl1-CaEXP or sfl2-CaEXP, respectively) SFL1-HA or SFL2-HA (-HA, 3'-triple-HA-tagged alleles of SFL1 or SFL2) under the control of a methionine-repressible promoter (Total samples = 8; 2xCaEXP-SFL1-HA, 2xCaEXP-SFL2-HA, 2xCaEXP control for SFL1-HA ChIP and 2xCaEXP control for SFL2-HA ChIP).
Project description:The differentiation of cells into distinct cell types, each of which is heritable for many generations, underlies many biological phenomena. White and opaque cells of the fungal pathogen Candida albicans are two such heritable cell types, each thought to be adapted to unique niches within their human host. To systematically investigate the differences between the two cell types, we performed strand-specific massively-parallel sequencing of RNA from C. albicans white and opaque cells. Combining the resulting data from both cell types, we first substantially re-annotated the C. albicans transcriptome, finding 1443 novel coding and non-coding transcriptionally active regions. Using the new annotation, we compared differences in transcript abundance between the two cell types with the genomic regions bound by the master regulator of the white-opaque switch (Wor1). We found that the revised transcriptional landscape considerably alters our understanding of the circuit governing differentiation. In particular, we can now resolve the poor concordance between binding of the master regulator and the differential expression of adjacent genes, a discrepancy observed in many other studies of cell differentiation. More than one third of the Wor1-bound differentially-expressed transcripts were previously unannotated, which explains the formerly puzzling presence of Wor1 at these positions along the genome. Indeed, many of these newly identified Wor1-regulated genes are non-coding and transcribed antisense to coding transcripts. We also found that 5' and 3' untranslated regions (UTRs) of mRNAs in the circuit are unusually long and that 5' UTRs often differ in length between white and opaque cells. These observations suggest that the use of alternative promoters is widespread in the circuit and that important regulatory information is carried in the long UTRs. Further analysis revealed that the revised Wor1 circuit bears several striking similarities to the Oct4 circuit that specifies the pluripotency of mammalian embryonic stem cells. Additional characteristics shared with the Oct4 circuit suggest a set of general hallmarks characteristic of heritable differentiation states in eukaryotes. RNA-Seq was applied to Candida albicans white and opaque cells to identify novel transcripts and UTRs that are differentially regulated between the two cell types. Two biological replicates each of white and opaque cell cultures. One of the white cell RNA samples was split just after isolation to allow a comparison of the poly(A)-selection and ribo-depletion sample preparation strategies.