β-D-glucuronidase gene from Escherichia coli is a functional reporter in the methylotrophic yeast Pichia pastoris

The Escherichia coli gene gusA was expressed in the methylotrophic yeast Pichia pastoris in a transcriptional fusion to the homologous methanol-inducible AOX1 promoter. Four recombinant clones were selected for expression studies in shake flask conditions and beta-D-glucuronidase (beta-GUS) activity was assayed each 24 h during the induction period. Regardless of the genomic integration patterns and the gene dosage, beta-GUS was functionally expressed and easily detected in all studied clones. The results obtained demonstrate the feasibility of using this bacterial enzyme as a reporter in Pichia pastoris.