Expression of Schizosaccharomyces pombe Thioltransferase and Thioredoxin Genes under Limited Growth Conditions

Schizosaccharomyces pombe gene encoding redox enzymes, such as thioltransferase (TTase) and thioredoxin (TRX), were previously cloned and induced by oxidative stress. In this investigation, their expressions were examined using $\beta$-galactosidase fusion plasmids. The expression of the two cloned genes appeared to be growth-dependent. The synthesis of $\beta$-galactosidase from the TTase-lacZ fusion was increased in the medium with the low glucose level, whereas it was significantly decreased in the medium without glucose or with galactose. It was also decreased in the nitrogen-limited medium. The synthesis of galactosidase from the TRX-lacZ fusion was unaffected by galactose or low glucose. However, it was lowered the absence of glucose. The synthesis of $\beta$-galactosidase from the TTase-lacZ fusion was shown to be enhanced in a higher medium pH. Our findings indicate that S. pombe TTase and TRX genes may be regulated by carbon and nitrogen sources, as well as medium pH.