Project description:The polymorphic yeast Candida albicans exists in blastospore and filamentous forms. The switch from one morphological state to the other coincides with the expression of virulence factors, which makes the yeast-to-hypha transition an attractive target for the development of new antifungal agents. Because an untapped therapeutic potential resides in small molecules that hinder C. albicans filamentation, we characterized the inhibitory effect of conjugated linoleic acid (CLA) on hyphal growth and addressed its mechanism of action. CLA inhibited hyphal growth in a dose-dependent fashion, in both liquid- and solid-inducing media. The fatty acid blocked germ tube formation and impeded hyphal elongation. Global transcriptional profiling revealed that CLA downregulated the expression of hypha-specific genes and abrogated the induction of several morphogenesis regulators, including RAS1, TEC1 and UME6. CLA’s repressive effect on TEC1 expression was Ras1-dependent, but Efg1-independent. CLA treatment resulted in the delocalization of Ras1 and its degradation, resulting in the downregulation of the Ras1-cAMP-PKA signaling pathway. This study provides the biological and molecular explanations that underlie CLA’s ability to inhibit hyphal growth in C. albicans.
Project description:The polymorphic yeast Candida albicans exists in blastospore and filamentous forms. The switch from one morphological state to the other coincides with the expression of virulence factors, which makes the yeast-to-hypha transition an attractive target for the development of new antifungal agents. Because an untapped therapeutic potential resides in small molecules that hinder C. albicans filamentation, we characterized the inhibitory effect of conjugated linoleic acid (CLA) on hyphal growth and addressed its mechanism of action. CLA inhibited hyphal growth in a dose-dependent fashion, in both liquid- and solid-inducing media. The fatty acid blocked germ tube formation and impeded hyphal elongation. Global transcriptional profiling revealed that CLA downregulated the expression of hypha-specific genes and abrogated the induction of several morphogenesis regulators, including RAS1, TEC1 and UME6. CLAM-bM-^@M-^Ys repressive effect on TEC1 expression was Ras1-dependent, but Efg1-independent. CLA treatment resulted in the delocalization of Ras1 and its degradation, resulting in the downregulation of the Ras1-cAMP-PKA signaling pathway. This study provides the biological and molecular explanations that underlie CLAM-bM-^@M-^Ys ability to inhibit hyphal growth in C. albicans. Two-color experimental design that consistently used growth in Spider Media at 30M-bM-^DM-^C as the control. We tested the effect of high temperature as well as the effect of adding 100 mM-BM-5 CLA at either low or high temperature. RNA from each replicate came from independent cultures.
Project description:Our genetic screen reveals that deletion of CTM1, which abolishes the lysine trimethylation of cytochrome c (Cyc1), results in inhibition of hyphal morphogenesis in Candida albicans. Similar results are observed in the unmethylatable Cyc1 mutant (cyc1K79A). To elucidate how unmethylated Cyc1 inhibits hyphal growth, we performed RNA-Seq analysis by comparing WT (BWP17), ctm1∆/∆, and cyc1K79A cells grown in yeast and hyphal condition. Consistent with previous published data, many hyphal specific genes (HSGs), such as ALS3, ECE1, HWP1, and UME6, are upregulated while three major hyphal suppressor genes, TUP1, NRG1, and RFG1, are downregulated when WT cells switch from yeast to hyphal growth. Similar changes are observed in ctm1Δ/Δ and cyc1K79A cells upon hyphal induction, even though most mutant cells maintain yeast morphology throughout the induction. Further comparisons reveal that the basal transcriptional levels of HSGs are much lower in ctm1Δ/Δ and cyc1K79A cells than those in WT cells. Upon hyphal induction, the levels of HSGs in ctm1Δ/Δ and cyc1K79A cells increase but still remain lower than their basal levels in WT cells. In contrast, the hyphal suppressor genes (especially NRG1) exhibit much higher basal transcriptional levels in ctm1Δ/Δ and cyc1K79A cells than in WT cells. Their transcriptional levels reduce upon hyphal induction but still remain higher than the basal levels in WT cells. Together, these data suggest that unmethylated Cyc1 inhibits hyphal morphogenesis via transcriptional regulation of HSGs and hyphal suppressor genes.
Project description:Candida albicans, the most common cause of human fungal infections, undergoes a reversible morphological transition from yeast to pseudohyphal and hyphal filaments, which is required for virulence. For many years, the relationship between global gene expression patterns associated with determination of specific C. albicans morphologies has remained obscure. Using a strain that can be genetically manipulated to sequentially transition from yeast to pseudohyphae to hyphae in the absence of complex environmental cues and upstream signaling pathways, we demonstrate by whole-genome transcriptional profiling that genes associated with pseudohyphae represent a subset of those associated hyphae and are generally expressed at lower levels; interestingly, no genes appeared to be expressed exclusively in pseudohyphae. Our results also strongly suggest that in addition to dosage, extended duration of filament-specific gene expression is sufficient to drive the C. albicans yeast-pseudohyphal-hyphal transition. Finally, we describe the first transcriptional profile of the C. albicans reverse hyphal-pseudohyphal-yeast transition and demonstrate that this transition not only involves down-regulation of known hyphal-specific genes but also differential expression of additional genes which have not previously been associated with the forward transition, including many involved in protein synthesis. These findings provide new insight into genome-wide mechanisms important for determining fungal morphology and suggest that in addition to similarities, there are also fundamental differences in global gene expression as pathogenic filamentous fungi undergo forward and reverse morphological transitions.
Project description:C. albicans is a dimorphic yeast which can switch from budding yeast and to hyphal forms and this property is essential for biofilm establishment and maturation. C. albicans undergoes this yeast-to-hyphal switch in response to high CO2. The purpose of this study is to use RNA-seq to investigate pathways whose genes are differentially expressed when C. albicans biofilms are grown in a physiologically relevant elevated (5%) CO2 environment compared to a low/atmospheric (0.03%) CO2 environment. We report that in C.albicans biofilms grown under 5% CO2 conditions, genes controlled by core biofilm regulatory transcription factors such as Brg1, Efg1, Ndt80, and Bcr1 are overall expressed at significantly higher levels compared to those grown in 0.03% CO2 conditions. We find that genes encoding glucose and amino acid transporters, as well as genes previously found to be involved in the response to Ketoconazole treatment, are significantly upregulated in 5% CO2 C. albicans biofilms. Overall, these data suggest a high CO2 environment enhances biofilm formation of C. albicans and may also increase antifungal tolerance of such biofilms.
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 “switch on/off” proteins to coordinate the regulation of C. albicans morphogenesis.
Project description:Azole resistance and varying degrees of cross-resistance to other members of the azole family in clinical isolates have been documented, which has necessitated additional and prolonged use of the antifungal agents available. 2-Amino-Nonyl-6-Methoxyl-Tetralin Muriate (10b), a novel chemical structural aminotetralin derivate, is synthesized as an antifungal agent and exibited strong antifungal activity. To further investigated the action mechanism, we used microarray analysis to investigate the genes expression profiles of C. albicans cells treated or untreated with 10b and found 957 genes were differentially expressed. Of them,457 showed a decrease in expression and 500 showed an increase in expression. 33 down-regulated genes were involved in glycolysis (e.g., PFK1, CDC19 and HXK2), fermentation (e.g., PDC11, ALD5 and ADH1) and respiratory electron transport chain (e.g., CBP3, COR1 and QCR8). 30 differentially expressed genes were found to relate to biofilm formation, filamentous or hyphal growth. It was noticed that striking up-regulation of SFL1 and marked down-regulation of YWP1 directly related to prevent C. albicans from changing its morphology from the yeast form to the hyphal. Two genes related to specifically hydrolyzing beta-1, 3 glucan (e.g., XOG1) and chitin (e.g., CHT1) were significantly increased. 40 overexpressed genes and 15 down-regulated genes were related to the lipid metabolic process. Of them, Eight were directly linked to ergosterol biosynthesis, including ERG2, ERG6 and ERG11. 99 genes related to translation were down-regulated following exposure to 10b, which account for 21.66% in down-regulated genes. This suggested that translation might be lower in SC5314 cells exposed to 10b than in control. Total RNA from the control SC5314 cells and 10b-treated SC5314 cells were used to generate target cDNA, and then hybridized to 8k Candida albicans Genome Array Genechips, representing about 7925 characterized Candida albicans genes. Two independent experiments were conducted. Reference strain was control SC5314 cells and test strain was SC5314 cells treated with 10b.
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).