title: Synergistic effect of upstream sequences, CCAAT box elements, and HSE sequences for enhanced expression of chimaeric heat shock genes in transgenic tobacco.
abstract: The thermoregulated expression of the soybean heat shock (hs) gene Gmhsp17.3-B is regulated via the heat shock promoter elements (HSEs), but full promoter activity requires additional sequences located upstream of the HSE-containing region. Structural features within this putative enhancer region include a run of simple sequences which are also present upstream of HSE-like sequences of other soybean hs genes, and three perfect CCAAT box sequences located immediately upstream from the most distal HSE of the promoter. A series of heterologous and homologous promoter fusions linked to the chloramphenicol acetyl transferase (CAT) gene was constructed and examined in transgenic tobacco plants. The region containing the AT-rich domain of the 5' flanking region was unable to direct transcription from the TATA box of a truncated delta CaMV35S promoter. Heat-inducible CAT activity was detectable when additional sequences from the native promoter containing three CCAAT boxes and a single HSE were present in the constructions. Complete reconstitution of the native hs promoter/enhancer region increased hs specific CAT activities only very little, but deletion of CCAAT box sequences reduced CAT expression five-fold. Our results suggest that AT-rich sequences have a moderate effect on thermoinducible expression levels of the soybean heat shock gene and that CCAAT box sequences act cooperatively with HSEs to increase the hs promoter activity.
authors.affiliation: University of Tübingen, Department of Genetics, FRG.
authors.forename: M
authors.initials: M
authors.lastname: Rieping
authors.forename: F
authors.initials: F
authors.lastname: Schöffl
mesh_terms: D001483:Base Sequence; D002678:Chimera; D004742:Enhancer Elements, Genetic / Q000502:physiology; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics*; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011995:Recombination, Genetic; D013025:Glycine max / Q000235:genetics*; D014026:Nicotiana / Q000235:genetics*
chemical_list: D006360:Heat-Shock Proteins