title: GT-1 binding site confers light responsive expression in transgenic tobacco.
abstract: Light-dependent expression of rbcS, the gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase, which is the key enzyme involved in carbon fixation in higher plants, is regulated at the transcriptional level. Sequence analysis of the gene has uncovered a conserved GT motif in the -150 to -100 region of many rbcS promoters. This motif serves as the binding site of a nuclear factor, designated GT-1. Analysis of site-specific mutants of pea rbcS-3A promoter demonstrated that GT-1 binding in vitro is correlated with light-responsive expression of the rbcS promoter in transgenic plants. However, it is not known whether factors other than GT-1 might also be required for activation of transcription by light. A synthetic tetramer of box II (TGTGTGGTTAATATG), the GT-1 binding site located between -152 to -138 of the rbcS-3A promoter, inserted upstream of a truncated cauliflower mosaic virus 35S promoter is sufficient to confer expression in leaves of transgenic tobacco. This expression occurs principally in chloroplast-containing cells, is induced by light, and is correlated with the ability of box II to bind GT-1 in vitro. The data show that the binding site for GT-1 is likely to be a part of the molecular light switch for rbcS activation.
authors.affiliation: Laboratory of Plant Molecular Biology, Rockefeller University, New York, NY 10021.
authors.forename: E
authors.initials: E
authors.lastname: Lam
authors.forename: N H
authors.initials: NH
authors.lastname: Chua
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D005822:Genetic Vectors; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics*; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic / Q000528:radiation effects; D014170:Transformation, Genetic
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D015500:Chloramphenicol O-Acetyltransferase; D012273:Ribulose-Bisphosphate Carboxylase