Evidence that part of a centromeric DNA region induces pseudohyphal growth in a dimorphic yeast, Candida maltosa.

Abstract

We observed that a YCp-type vector having the centromeric DNA (CEN) sequence previously isolated from the genome, but not a YRp-type vector lacking the CEN sequence, induced pseudohyphal growth in a dimorphic fungi, Candida maltosa, which had been shown to be closely related to Candida albicans by phylogenetic analysis. Deletion analysis of the CEN sequence revealed that the intact CEN sequence was not required for the induction, but part of it, having partial centromeric activity, was enough for the induction. By screening the gene library of this yeast for the sequences which induced pseudohyphal growth, we isolated three different DNA fragments which also had part of the centromere-like sequence. Partial centromeric activity of these fragments was confirmed by three criteria: low copy number and high stability of the plasmids carrying these fragments and rearrangement at high frequency of the plasmid DNA with one of these fragments plus the CEN sequence. Furthermore, when the GGTAGCG sequence commonly found in one copy in each of these four sequences was mutated in the CEN sequence by site-directed mutagenesis, both partial centromeric activity and pseudohyphal growth-inducing activity of the CEN sequence were lost. These results indicated that part of CEN region with partial centromeric activity induces pseudohyphal growth in C. maltosa. It is suggested that some cellular components which interact with the sequence containing GGTAGCG required for centromeric activity are involved in the regulation of the transition between yeast forms and pseudohyphal forms of the cells.