Abstract
We found that in Synechocystis PCC 6803 two glutathione peroxidase (GPX)-like proteins utilized NADPH, but not GSH, as an electron donor. To elucidate the physiological function of GPX-like proteins in S. 6803 cells, here we studied the supply of NADPH for GPX-like proteins and the effect of several stresses on the expression of two genes. The t-butyl hydroperoxide (t-BuOOH)-dependent evolutions of oxygen in wild type and mutant cells disrupted by a kanr cartridge gene indicated that activities of Gpx-1 and Gpx-2 are coupled with NADPH supplied from the photosynthetic electron transport system. By Northern blotting, gpx-1 transcripts were expressed under high light or by the treatment of t-BuOOH and salt, while gpx-2 was up-regulated to high light and salt stress conditions; it was induced within 15 min and then decreased. Interestingly, the transcript level of gpx-2 was not changed in response to the treatment of t-BuOOH.
