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Applied and Environmental Microbiology, June 1999, p. 2363-2368, Vol. 65, No. 6
Forest Products Laboratory, U.S. Department
of Agriculture, Forest Service, Madison, Wisconsin 53705, and
Department of Bacteriology, University of Wisconsin, Madison, Wisconsin
53706
Received 15 December 1998/Accepted 5 April 1999
We studied the expression of the genes encoding group I alcohol
dehydrogenases (PsADH1 and PsADH2) in the
xylose-fermenting yeast Pichia stipitis CBS 6054. The cells
expressed PsADH1 approximately 10 times higher under
oxygen-limited conditions than under fully aerobic conditions when
cultivated on xylose. Transcripts of PsADH2 were not
detectable under either aeration condition. We used a PsADH1::lacZ fusion to monitor
PsADH1 expression and found that expression increased as
oxygen decreased. The level of PsADH1 transcript was
repressed about 10-fold in cells grown in the presence of heme under
oxygen-limited conditions. Concomitantly with the induction of
PsADH1, PsCYC1 expression was repressed. These
results indicate that oxygen availability regulates PsADH1
expression and that regulation may be mediated by heme. The regulation
of PsADH2 expression was also examined in other genetic
backgrounds. Disruption of PsADH1 dramatically increased
PsADH2 expression on nonfermentable carbon sources under
fully aerobic conditions, indicating that the expression of
PsADH2 is subject to feedback regulation under these conditions.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Transcriptional Control of ADH Genes in the
Xylose-Fermenting Yeast Pichia stipitis
and
*
Corresponding author. Mailing address: Institute for
Microbial and Biochemical Technology, Forest Products Laboratory, One Gifford Pinchot Dr., Madison, WI 53705. Phone: (608) 231-9453. Fax:
(608) 231-9262. E-mail: twjeffri{at}facstaff.wisc.edu.
Present address: Gene Regulation and Chromosome Biology Laboratory,
NCI-Frederick Cancer Research and Development Center, ABL-Basic
Research Program, Frederick, MD 21702-1201.
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