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Quantitative transcriptome analysis of C. albicans biofilms grown in high and low carbon dioxide conditions.

ABSTRACT: 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.

ORGANISM(S): Candida albicans

PROVIDER: GSE172004 | GEO | 2021/04/14

REPOSITORIES: GEO

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Project description:Candida albicans can stochastically switch between two phenotypes, white and opaque. Opaque cells are the sexually competent form of C. albicans and therefore undergo efficient polarized growth and mating in the presence of pheromone. In contrast, white cells cannot mate, but are induced - under a specialized set of conditions - to form biofilms in response to pheromone. In this work, we compare the genetic regulation of such "pheromone-stimulated" biofilms with that of "conventional" C. albicans biofilms. In particular, we examined a network of six transcriptional regulators (Bcr1, Brg1, Efg1, Tec1, Ndt80, and Rob1) that mediate conventional biofilm formation for their potential roles in pheromone-stimulated biofilm formation. We show that four of the six transcription factors (Bcr1, Brg1, Rob1, and Tec1) promote formation of both conventional and pheromone-stimulated biofilms, indicating they play general roles in cell cohesion and biofilm development. In addition, we identify the master transcriptional regulator of pheromone-stimulated biofilms as C. albicans Cph1, ortholog of Saccharomyces cerevisiae Ste12. Cph1 regulates mating in C. albicans opaque cells, and here we show that Cph1 is also essential for pheromone-stimulated biofilm formation in white cells. In contrast, Cph1 is dispensable for the formation of conventional biofilms. The regulation of pheromone- stimulated biofilm formation was further investigated by transcriptional profiling and genetic analyses. These studies identified 206 genes that are induced by pheromone signaling during biofilm formation. One of these genes, HGC1, is shown to be required for both conventional and pheromone-stimulated biofilm formation. Taken together, these observations compare and contrast the regulation of conventional and pheromone-stimulated biofilm formation in C. albicans, and demonstrate that Cph1 is required for the latter, but not the former. 4 condition experiment: white and opaque cells in planktonic and pheromone-induced biofilm conditions with and without alpha pheromone. WT strain (P37005), the tec1 mutant strain and the cph1 mutant strain

Project description:Candida albicans is an opportunistic fungal pathogen that can infect oral mucosal surfaces despite being under continuous flow from saliva. Previous studies have shown that under specific conditions C. albicans will form microcolonies that more closely resemble the biofilms formed in vivo than standard in vitro biofilm models. However, very little is known about these microcolonies, particularly genomic differences between these specialized biofilm structures and the traditional in vitro biofilms. In this study, we used a novel flow system, in which C. albicans spontaneously forms microcolonies, to further characterize the architecture of fungal microcolonies and their genomics compared to non-microcolony conditions. Fungal microcolonies arise from radially branching filamentous hyphae that increasingly intertwine with one another to form extremely dense biofilms, and closely resemble the architecture of in vivo oropharyngeal candidiasis. We identified 20 core microcolony genes that were differentially regulated in flow-induced microcolonies using RNA-seq. These genes included HWP1, ECE1, IHD1, PLB1, HYR1, PGA10, and SAP5. To better understand the regulatory elements for microcolonies, we utilized a predictive algorithm to discover ten transcriptional regulators potentially involved in microcolony formation. Of these transcription factors, we found that six played a key role in microcolony formation and development (Rob1, Ndt80, Efg1, Sfl1, Sfl2, and Nrg1). We also found that Hwp1, Sap5, Pga10, and all the microcolony regulators promoted adhesion and invasion of the microcolonies to oral epithelium. Furthermore, epithelial cells infected with deletion mutants of ROB1, NDT80, SFL2, EFG1, and MCM1 had reduced immune response, evidenced by reduced phosphorylation of MKP1 and c-Fos, key signal transducers in the hyphal invasion response. This profile of microcolony transcriptional regulators more closely reflects Sfl1 and Sfl2 hyphal regulatory networks than biofilm regulatory networks, suggesting that hyphal morphogenesis plays a more central role in the development of flow-induced microcolonies.

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Quantitative transcriptome analysis of C. albicans biofilms grown in high and low carbon dioxide conditions.

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