The Promoter of the Gene for Plastidic Glutamine Synthetase (GS2) fromRice Is Developmentally Regulated and Exhibits Substrate-Induced Expression in Transgenic Tobacco Plants

A 1.3-kb fragment from the 5'-flanking region of the RGS-38gene, which encodes the plastidic glutamine synthetase in Oryzasativa L., was fused to a ß-glucuronidase (GUS) reportergene and introduced into Nicotiana tabacum by Agrobacterium-mediatedtransformation. The promoter directed GUS expression, both inleaves and in roots, and the expression of GUS was regulatedby light. The GUS activity was high in the mature leaves ofthe transgenic tobacco plants, in marked contrast to the activityof the GS1 promoter. The GS2 promoter also responded to externallyapplied ammonia, as is the case for the GS1 promoter. Theseresults suggest that the cis-acting regulatory elements thatcontrol the response to ammonia, a substrate for glutamine synthetase,are located within a 1.3-kb region of the promoter. (Received October 1, 1991; Accepted January 20, 1992)