GSE117433
Candida albicans Sfl1/Sfl2 regulatory network drives the formation of pathogenic microcolonies.
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. Overall design: RNA expression profiles of 24 h C. albicansbiofilms grown under flow (at 37 °C or 23 °C) or static (at 37°C) conditions generated by duplicate analyses using Illumina HiSeq 2500