Abstract
In higher plants, expression of nitrate transporter(s) (NRT), nitrate reductase (NR), and nitrite reductase (NiR) is regulated both positively and negatively at the transcription level; Gln or its metabolite(s) downregulates transcription, whereas nitrate and/or nitrite upregulate transcription. In this study, we cloned the NR cDNAs from the moss P. patens and partially characterized them. P. patens was found to express two closely related species of NR mRNA when grown with nitrate. The deduced NR proteins are 80% identical to each other and 56% and 47% identical to the NR proteins from Arabidopsis thaliana and Chlamydomonas reinhartii, respectively. Expression of the NR genes is activated by nitrate and inhibited by ammonium. These results are essentially the same as those reported for higher plant systems, showing that P. patens can be used as a model plant for the studies on the mechanism of regulation of the nitrate assimilation genes.
