Functional analysis of sequences required for transcriptional activation of a soybean heat shock gene in transgenic tobacco plants

The 5′ DNA sequences involved in the thermal inducibility of the soybean heat shock gene hs6871 were analysed in transgenic tobacco plants. The transcriptional activity of various in vitro generated deletion mutants was examined by Northern blot analysis, S1 nuclease mapping and dot‐blot hybridization. At least 181 bp upstream from the translational start site are sufficient for thermal induction at 40°C and correct initiation of transcripts. Full promoter activity with the induction of wild‐type levels of transcripts requires additional upstream sequences contained within 439 bp 5′ to the coding sequence. Our results suggest that faithful regulation and the generation of high levels of hs6871‐specific mRNA depend on the presence of sequences which show homology to the 14‐bp heat shock consensus element of Drosophila and, in addition, on as yet unidentified enhancer‐like upstream sequences.