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Abstract
Opportunistic fungal pathogen Candida albicans often encounters host niches where it must survive on alternative carbon sources alone. In Saccharomyces cerevisiae, transcription factor Adr1 activates genes required for acetate and glycerol utilization. However, previous researchers found that CaADR1 deletion mutants have robust growth on acetate and glycerol. We have found that Adr1 is required for growth on citrate. This phenotype is manifested among multiple strains isolated from all known host niches. RNA sequencing and Nanostring analyses of adr1Δ/Δ and wild-type strains show that Adr1 is required for expression of many genes within the TCA cycle and gluconeogenesis. Major targets include enzymes Mdh1 and Pck1. Unexpectedly, one highly Adr1-dependent gene, HGT17, is not within the TCA cycle and gluconeogenesis. HGT17 is a putative glucose transporter. Phenotypic analyses support the hypothesis that Hgt17 is able to transport citrate. Further exploration of citrate utilization uncovered a possible citrate utilization pathway involving Eed1 and Adr1 regulating the expression of Hgt17. Our data underscore the importance of Adr1 and Hgt17 in the utilization of citrate as a carbon source in C. albicans.