Development of a promoter assay system for the flavinogenic yeast Candida famata based on the Kluyveromyces lactis β-galactosidase LAC4 reporter gene

A system for analysis of promoter activities was developed for the flavinogenic yeast Candida famata. The Kluyveromyces lactis LAC4 gene encoding β-galactosidase as a reporter gene and C. famata mutant lac4 unable for lactose utilization as a recipient strain were used in the system. The Escherichia coli β-galactosidase gene lacZ could not be used in the system because of difference in codon usage between the bacterium and C. famata. The C. famata mutant lac4 was transformed with the plasmid containing analyzable promoters fused with the promoterless LAC4 gene. Resulting transformants (unlike the mutant lac4) were able to utilize lactose as sole carbon source. The promoter strength was estimated on the basis of β-galactosidase activity assayed in the transformants. Different promoters of C. famata and Debaryomyces hansenii (a teleomorph of C. famata) were analyzed using this approach. The results showed an adequacy of the K. lactis LAC4 gene for evaluation of promoter strength in C. famata.