Functional characterization of the CaFTH1 gene in Candida albicans

Abstract:

[Objective] CaFTH1 gene encodes a putative iron permease in Candida albicans. To investigate the role of CaFTH1 in cellular iron metabolism and vacuolar function, we constructed fth1?/? single gene deletion and fth1?/?fet33?/? double deletion mutants. [Methods] Sequence alignment and analysis were performed by the relevant bioinformatic software. Effect of iron avaibility on the expression of CaFTH1 was conducted by real-time PCR. We constructed the fth1?/? and fth1?/?fet33?/? mutants by PCR-mediated gene disruption. We monitored the change of cellular iron content of the mutants by using atomic absorption spectroscopy (AAS), and explored the growth status under iron-limited and hyphal-inducing conditions. Furthermore, we also investigated the effect of gene deletions on vacuolar function by metabolic shift experiment. [Results] Sequence alignment revealed that C. albicans CaFth1 protein is a member of Ftr1 iron permease superfamily, with the highest homology with S. cerevisiae vacuolar membrane proteins ScFth1. Iron starvation induced the expression of CaFTH1, while iron repletion decreased its mRNA levels. Deletion of CaFTH1 resulted in decreased cellular iron content, and deletion of CaFET33 on the basis of fth1?/? mutant further decreased cellular iron content. For the metabolic shift experiment, the fth1?/?fet33?/? mutant also exhibited growth defect under iron-limited conditions. In addition, the fth1?/?fet33?/? mutant showed distinct wrinkled colonies in some solid hyphal-inducing conditions, while the fth1?/?fet33?/? mutant displayed increased aggregation ability in the presence of liquid-inducing cues. [Conclusion] CaFTH1 is induced in response to iron limitation, and plays an important role in maintaining C. albicans cellular iron homoeostasis and vacuolar function. Double deletion of CaFTH1 and CaFET33 genes affects the colonial morphology and hyphal aggregation.