Morphogenic regulator EFG1 affects the drug susceptibilities of pathogenic Candida albicans

This study shows that the morphogenic regulator EFG1 level affects the drug susceptibilities of Candida albicans when grown on solid growth media. The Deltaefg1 mutant showed sensitivity particularly to those drugs that target ergosterol or its metabolism. Efg1p disruption showed a gene-dosage effect on drug susceptibilities and resulted in enhanced susceptibility to drugs in the homozygous mutant as compared with the wild type, heterozygous and revertant strains. The enhanced sensitivity to drugs was independent of the status of ATP-binding cassette and MFS multidrug efflux pumps of C. albicans. The Deltaefg1 mutant displayed increased membrane fluidity that coincided with the downregulation of ERG11 and upregulation of OLE1 and ERG3, leading to enhanced passive diffusion of drugs. Interestingly, Deltaefg1 mutant cells displayed enhanced levels of endogenous ROS levels. Notably, the higher levels of ROS in the Deltaefg1 mutant could be reversed by the addition of antioxidants. However, the restoration of ROS levels did not reverse the drug sensitivities of the Deltaefg1 mutant. Taken together, we, for the first time, establish a new role to EFG1 in affecting the drug susceptibilities of C. albicans cells, independent of ROS and known drug efflux mechanisms.