THE PROMOTER OF THE GENE FOR GLUTAMINE-SYNTHETASE FROM RICE SHOWS ORGAN-SPECIFIC AND SUBSTRATE-INDUCED EXPRESSION IN TRANSGENIC TOBACCO PLANTS

A 2-kb fragment from the 5'-flanking region of the RGS-28 gene, which encodes the cytosolic glutamine synthetase in Oryza sativa L., was fused to a beta-glucuronidase (GUS) reporter gene and introduced into Nicotiana tabacum by Agrobacterium-mediated transformation. The promoter was predominantly active in the leaves of transgenic plants, as it is in authentic rice plants. The promoter also responded to externally applied ammonium ions. It is suggested that the cis-acting regulatory elements responsible for the recognition of the leaf as a site of synthesis and of ammonia, a substrate for glutamine synthetase, are located within a 2-kb region of the promoter.