A Genome Sequence Survey Shows that the Pathogenic Yeast Candida parapsilosis Has a Defective MTLa1 Allele at Its Mating Type Locus

摘要

Candida parapsilosis is responsible for ca. 15% of Candida infections and is of particular concern in neonates and surgical intensive care patients. The related species Candida albicans has recently been shown to possess a functional mating pathway. To analyze the analogous pathway in C. parapsilosis, we carried out a genome sequence survey of the type strain. We identified ca. 3,900 genes, with an average amino acid identity of 59% with C. albicans. Of these, 23 are predicted to be predominantly involved in mating. We identified a genomic locus homologous to the MTL>a mating type locus of C. albicans, but the C. parapsilosis type strain has at least two internal stop codons in the MTL>a1 open reading frame, and two predicted introns are not spliced. These stop codons were present in MTL>a1 of all eight C. parapsilosis isolates tested. Furthermore, we found that all isolates of C. parapsilosis tested appear to contain only the MTL>a idiomorph at the presumptive mating locus, unlike C. albicans and C. dubliniensis. MTLα sequences are present but at a different chromosomal location. It is therefore likely that all (or at least the majority) of C. parapsilosis isolates have a mating pathway that is either defective or substantially different from that of C. albicans.