INDUCIBLE EXPRESSION OF YEAST MITOCHONDRIAL CITRATE SYNTHASE IN ASPERGILLUS-NIDULANS

The coding region of the mitochondrial citrate synthase gene (CIT1) fr om Saccharomyces cerevisiae was amplified by PCR and cloned into an ex pression vector (pAL4) downstream of the alcohol dehydrogenase (alcA) promoter of Aspergillus nidulans to yield pALCS1. Transformation of A. nidulans A773 with this construct gave stable transformants, AYC#I an d AYC#2, that were phenotypically stable for several mitotic divisions . Southern blot analysis showed that the CIT1 gene was successfully in tegrated into the chromosomes of the transformants. Western blot analy sis and enzymatic assay for citrate synthase revealed that the integra ted yeast gene was subject to inducible expression controlled by alcA promoter, which can be induced by threonine.