A genetic transformation system based on trp1 complementation in Candida glycerinogenes

Candida glycerinogenes WL2002-5 is an osmotolerant yeast used for the commercial production of glycerol. The TRP1 gene of Candida glycerinogenes (CgTRP1), encoding phosphoribosylanthranilate isomerase (PRAI) was cloned by complementation of the trp1 mutation of Saccharomyces cerevisiae W303-1A. DNA sequence analysis revealed a 735 bp open reading frame (ORF) encoding a polypeptide of 244 amino acids, which shared 32.9 ~ 49.2% amino acid sequence similarity to PRAI proteins from other species of Saccharomycetales. A trp1 auxotrophic mutant of C. glycerinogenes was selected in medium containing 5-fluoroanthranilic acid, and confirmed by functional and sequence analysis. An integrative vector was constructed with the 18S rDNA gene as integration target and CgTRP1 gene as selectable marker. The trp1 mutant of C. glycerinogenes was transformed with integrative vector, transformants were screened by trp1 complementation. Diagnostic PCR show that the plasmid could be integrated in the site of the 18S rDNA gene of C. glycerinogenes.