The in vitro expression of SAP6 gene in Candida albicans morphogenesis mutants under human serum influence

Candida albicans morphogenesis enables colonization of various niches in host body. Various hyphae-dependent genes have been described. Among them secreted aspartyl proteinases (Saps) play a central role in pathogenesis. Candida albicans SAP4-6 genes encode secretory aspartyl proteinases Sap4-6, which are involved in hyphae formation and virulence. Transcriptional factors Cph1 (STE-like transcription factor) and Efg1 (positive regulator of filamentous growth) govern the expression of several C. albicans genes and contribute to morphogenesis. Given that SAP4-6 expression is regulated during hyphal formation, in this study we investigated the degree of SAP6 expression in strains with deletion of EFG1 and/or CPH1 regulating morphological transition in comparison to clinical isolate. The SAP6 gene expression level was measured with the application of quantitative real-time PCR, after 18 h incubation in human serum at body temperature. Moreover, scanning electron microscopy was applied to characterize morphologies of the tested strains. The estimated SAP6 expression was considerably high in the Δcph1/Δcph1 strain. Furthermore, introduction of the functional copy of CPH1 to this mutant resulted in upregulation of SAP6 expression. In the contrary, in the strains deleted for either EFG1 or both CPH1 and EFG1 factors, SAP6 expression was significantly altered. Reintroduction of one copy of EFG1 to Δcph1/Δcph1 Δefg1/Δefg1 restored hyphae formation, yet SAP6 expression remained altered in this strain. This might suggest that SAP6 is hyphae-independent and is not solely regulated by Efg1 but also by Cph1. Moreover, other transcriptional factors may regulate this gene expression under human serum influence. © 2013 Versita Warsaw and Springer-Verlag Wien.