Use of the Iron-Responsive Promoter for Regulated Expression in Candida albicans.

Engineered conditional gene expression is used in appraisal of gene function and pathway relationships. For pathogens like the fungus Candida albicans, conditional expression systems are most useful if they are active in the infection environment and if they can be utilized in multiple clinical isolates. Here, we describe such a system. It employs the promoter and can be implemented with a few PCRs. We validated the system with promoter fusions to two genes that promote filamentation and polarized growth, and , and with Δ/Δ mutants, which are defective in an activator of filamentous growth. An promoter fusion to either gene enabled filamentous growth of an Δ/Δ mutant of strain SC5314 in iron-limited media, including RPMI with serum and yeast extract-peptone-dextrose with bathophenanthrolinedisulfonic acid. The fusion promoted filamentation of Δ/Δ mutants in RPMI with serum of four other clinical C. albicans isolates as well. In a mouse model of disseminated candidiasis, the fusion promoted filamentation of the SC5314 Δ/Δ mutant in kidney tissue, an indication that the promoter is active in the iron-limited host environment. The promoter expands the conditional expression toolkit for C. albicans genetics. Genetic strategies have been vital for mechanistic analysis of biological processes. Here, we describe a genetic tool for the fungal pathogen Candida albicans.