Cloning and characterization of EPD2, a gene required for efficient pseudohyphal formation of a dimorphic yeast, Candida maltosa

Candida maltosa is a dimorphic fungus and its pseudohyphal growth is partly induced by additional copies of the centromeric DNA (CEN) region(1)), or n-alkane. In the course of analyzing the induction mechanism of pseudohyphal growth, we isolated EPD1, which is similar in sequence to PHR1 and PHR2 of Candida albicans. Epd1p could be involved in cell wall maintenance and is essential for pseudohyphal growth induced by CEN and n-hexadecane at pH 4 and by n-hexadecane at pH 7.(2)) In this paper, we cloned EPD2 of C. maltosa, which is highly similar to EPD1, PNRI, and PHR2. The transcription of EPD2 is induced strongly when cells are grown in SD medium of higher pH (pH 7), but not in SD medium of lower pH (pH 4). This pattern of expression was an inverse of that of EPD1. This alternate expression is similar to that between PHR1 and PHR2. The expression of EPD2 was much higher when C. maltosa was grown on the n-hexadecane solid medium than grown in the n-hexadecane liquid medium. The efficiency of pseudohyphal formation of an epd2 null mutant on n-hexadecane medium at pH 7 or 7.5 was lower than that of the wild-type strain. These results suggest that Epd2p is required for efficient pseudohyphal formation induced by n-hexadecane in the medium at pH 7.