Identification of light- and nitrate-responsive regions of the nitrate reductase promoter from birch

The regulation of nitrate reductase (NR) gene expression in higher plants i nvolves both internal and external factors. In birch (Betula, pendula Roth) , the transcription of the NR gene depends on light and nitrate in both lea ves and roots. In order to investigate the transcriptional regulation of th e birch NR gene, a 1.6-kb 5' flanking sequence of the NR gene was isolated, sequenced, and the transcription start site was determined. The 1.6 kb seq uence and eight 5' deleted versions of the promoter sequence were each fuse d with the beta-glucuronidase (GUS) reporter gene (uidA) and introduced int o Nicotiana plumbaginifolia. GUS expression was examined in primary transfo rmants that were transferred from dark to light or from a medium without ni trate to a nitrate-containing medium. A detailed analysis revealed the pres ence of light- and nitrate-responsive promoter regions, respectively. Sever al promoter regions conferred a differential expression of the GUS gene bet ween leaves and roots. (C) 2000 Elsevier Science Ireland Ltd. All rights re served.