[Chitin synthase (CHS) gene analysis of dermatophytes]

About 620-bp genomic DNA fragments of CHS1 genes were amplified from 13 species of dermatophytes by polymerase chain reaction (PCR) and sequenced. The phylogenetic analysis of CHS1 gene fragments of these dermatophyte species revealed that 3 genera of Epidermophyton, Microsporum and Trichophyton were genetically different from each other. The molecular analysis of CHS1 genes will provide useful information for the identification of dermatophytes. The species-specific primers were designed from the nucleotide sequences of CHS1 gene in 3 teleomorphs of T. mentagrophytes. Using these primers the PCR analysis identified the clinical isolates of T. mentagrophytes from rabbit as A. benhamiae. By PCR analysis with the dermatophyte specific primer pair, dermatophyte DNA could be diagnosed directly and rapidly in clinical skin samples. The full length of CHS1 and CHS2 genes of Arthroderma benhamiae (one of the teleomorphs of T. mentagrophytes) was sequenced by 5'-RACE and 3'-RACE methods using cDNA as a template. The full length cDNA sequences of CHS1 gene (3158bp) and CHS2 gene (3392bp) were proved to encode 890 and 419 amino acids, respectively. The amino acid sequences of A. benhamiae CHS1 and CHS2 in the conserved regions shared, respectively, about 70% and 80% sequence similarity with those of the other filamentous ascomycetes registered in the data base of the GeneBank. RT-PCR analysis suggested that chitin synthase inhibitors (nikkomycin Z and polyoxin D) might stimulate the expression of CHS1 mRNA in A. benhamiae, and not the expression of CHS2 mRNA.