Characterization of Candida albicans ferric reductase genes in response to environmental stresses

Abstract:

Abstract:［Objective］Ferric reductases play a central role in iron acquisition and mobilization in C．albicans．This study focuses on stress response strategies exhibited by several ferric reductase genes through function and expression analyses．［Methods］ Northern blot analysis was used to examine ferric reductase genes expression levels in different iron deficiency．We constructed ferric reductase-null mutants by a PCR-based homologous recombination，and examined the effects of gene deletion on cell-surface ferric reductase activity and growth ability under different conditions． Sub-cellular localization of Frp1-GFP fusion was imaged and analyzed by confocal laser scanning fluorescence microscopy． ［Ｒesults］FRE10 was highly expressed at acidic pH，compared to that at alkaline pH，whereas the expression of FＲE2 was just the opposite． Deletion of FＲE10 resulted in a significant decreased surface reductase activity at acidic pH，with 75. 5% downregulation compared to wild-type levels．The fre2Δ/Δ mutant showed significantly attenuated growth ability and cellsurface ferric reductase activity at alkaline pH．Sub-cellular localization revealed that the green fluorescence was accumulated in the vacuoles．［Conclusion］The expression of both FRE10 and FRE2 is induced in a pH-dependent manner．FRE2 encodes a major cell surface ferric reductase under alkaline pH condition．Frp1 localizes to the vacuole，and might support mobilization and transport of vacuolar ferric iron stores．