beta-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 Pi chia pastoris in a transcriptional fusion to the homologous methanol-induci ble AOX1 promoter. Four recombinant clones were selected for expression stu dies in shake flask conditions and beta-D-glucuronidase (beta-GUS) activity was assayed each 24 h during the induction period. Regardless of the genom ic integration patterns and the gene dosage, beta-GUS was functionally expr essed and easily detected in all studied clones. The results obtained demon strate the feasibility of using this bacterial enzyme as a reporter in Pich ia pastoris.