Cho J Y, Jeffries T W
Forest Products Laboratory, U.S. Department of Agriculture, Forest Service, Madison, Wisconsin 53705, USA.
Appl Environ Microbiol. 1999 Jun;65(6):2363-8. doi: 10.1128/AEM.65.6.2363-2368.1999.
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.
我们研究了编码I类乙醇脱氢酶（PsADH1和PsADH2）的基因在木糖发酵酵母树干毕赤酵母CBS 6054中的表达情况。当在木糖上培养时，细胞在氧限制条件下表达PsADH1的水平比在完全好氧条件下高约10倍。在两种通气条件下均未检测到PsADH2的转录本。我们使用PsADH1::lacZ融合体来监测PsADH1的表达，发现随着氧气减少，表达增加。在氧限制条件下，在血红素存在下生长的细胞中，PsADH1转录本水平被抑制了约10倍。伴随着PsADH1的诱导，PsCYC1的表达被抑制。这些结果表明，氧气可利用性调节PsADH1的表达，并且这种调节可能由血红素介导。我们还在其他遗传背景下研究了PsADH2表达的调控。在完全好氧条件下，破坏PsADH1会显著增加PsADH2在非发酵碳源上的表达，表明在这些条件下PsADH2的表达受到反馈调节。
