Effect of commonly used herbicides on the virulence factor CDR1 in Candida albicans

The ubiquitous yeast Candida albicans becomes a troublesome pathogen by inducing virulence factors in response to environmental stimuli. Among these virulence factors is a drug-exporting transport protein, Cdr1p, which renders cells resistant to certain antifungal drugs. The expression of the CDR1 gene responds to a wide spectrum of stimuli, including drugs, heat shock, and steroid hormones. The aim of the present study is to characterize the effects of commonly used herbicides on the expression of CDR1. Following exposure of C. albicans cultures to varying doses of herbicides and azole drugs, CDR1 expression was quantified by flow cytometry using a reporter strain in which expression of a green fluorescent protein is under the control of the CDR1 promoter. Correlating CDR1 expression with cell growth and survival revealed that—similar to antifungal azole drugs— herbicides induce CDR1 expression only at inhibitory doses. It is concluded that none of the tested herbicides mimics the worrisome action of hormones, which increase virulence without reducing survival.