Exploring the effects of culture conditions on Yapsin () gene expression in .

, previously known as , has the great potential to cause systemic fungal infections despite its similarity to baker's yeast. Its pathogenicity is attributed to the production of numerous virulence factors, among which the genes (-) encoding aspartyl proteases have yet to be sufficiently characterized, and limited studies suggest their involvement in cellular homeostasis. The study's novelty is an investigation of the role of in ability to adapt to different host environments. For this purpose, we isolated RNA from cells grown in both host niche-mimicking culture media, such as artificial saliva (AS) and vagina-simulating media (VS), as well as standard yeast media (RPMI 1640 and YPDA). We then performed quantitative real-time PCR to evaluate gene expression at different growth phases. At the early logarithmic phase, we observed a general increase in the expression levels of genes; however, at the stationary phase, high expression levels were maintained for in RPMI 1640 and YPDA media and in RPMI 1640 and AS media. In addition, although the VS medium does not promote the proliferation of , the yeast can survive in an acidic environment, and the significantly overexpressed gene is . These findings underscore the significant modulation of gene expression in response to external environmental conditions. This research provides insights into the molecular basis of pathogenicity and highlights new potential targets for antifungal therapy.