ISOLATION OF THE SPINACH NITRITE REDUCTASE GENE PROMOTER WHICH CONFERS NITRATE INDUCIBILITY ON GUS GENE-EXPRESSION IN TRANSGENIC TOBACCO

Nitrite reductase is the second enzyme in the nitrate assimilatory pathway. The transcription of this gene is regulated by nitrate as well as a variety of other environmental and developmental factors. Genomic clones containing the entire nitrite reductase gene have been isolated from a spinach genomic library and sequenced. The sequence is identical in the transcribed region to a previously isolated spinach NiR cDNA clone (Black et al., 1988) except for the presence of three introns. The analysis of the genomic clones and DNA blot hybridization demonstrates that there is a single NiR gene per haploid genome in spinach. This is in contrast to what has been found for other plant species. The transcription initiation site has been determined by S 1 mapping and the 5' upstream region has been used to regulate the GUS reporter gene in transgenic tobacco plants. This gene was found to be regulated by the addition of nitrate in the transgenic plants.