Regulation of filamentation in the human fungal pathogen C andida tropicalis

Summary The yeast–filament transition is essential for the virulence of a variety of fungi that are pathogenic to humans. N‐acetylglucosamine ( GlcNA c) is a potent inducer of filamentation in C andida albicans and thermally dimorphic fungi such as H istoplasma capsulatum and B lastomyces dermatitidis . However, GlcNA c suppresses rather than promotes filamentation in C andida tropicalis , a fungal species that is closely related to C . albicans . Despite the intensive study in C . albicans , the regulatory mechanism of filamentation is poorly understood. In this study, we demonstrate that the c AMP signaling pathway plays a central role in the regulation of filamentation in C . tropicalis . By screening an overexpression library of 156 transcription factors, we have identified approximately 40 regulators of filamentous growth. Although most of the regulators (e.g., T ec1, G at2, N rg1, S fl1, S fl2 and A sh1) demonstrate a conserved role in the regulation of filamentation, similar to their homologues in C . albicans or S accharomyces cerevisiae , a number of transcription factors (e.g., W or1, B cr1, S tp4, E fh1, C sr1 and Z cf17) play a specific role in C . tropicalis . Our findings indicate that multiple interconnected signaling pathways are involved in the regulation of filamentation in C . tropicalis . These mechanisms have conserved and divergent features among different C andida species.