The DNA sequence analysis of soybean heat-shock genes and identification of possible regulatory promoter elements

Abstract

The soybean possesses a gene family encoding the major low mol. wt. heat-shock proteins of 15-18 kd. We have determined the primary DNA sequences of two of the genes, both located on the same subgenomic DNA fragment. The protein coding regions are characterized by long uninterrupted open reading frames and by sequence homology of 92% and 100% with a heat-shock specific cDNA. One protein sequence deduced from the completely cloned gene hs6871 is composed of 153 amino acids with a total mol. wt. of 17.3 kd; the other protein is a truncated polypeptide containing 73 amino acids at the carboxy-terminal end of an incompletely cloned heat-shock gene designated hs6834. Investigations of the hydrophilic/hydrophobic characteristics of the polypeptides revealed a conservation of structural features between heat-shock proteins from soybean, Caenorhabditis and Drosophila and mammalian lens alpha-crystallin. The 5' end of the soybean heat-shock gene hs6871 was mapped by S1 nuclease at a position which is 100 nucleotides upstream from the translation start codon and 25 nucleotides downstream from a TATA-box sequence. Six other potential promoter elements which are homologous to the Drosophila heat-shock consensus sequence CT-GAA-TTC-AG-, are present within 150 nucleotides upstream from the TATA-box. The possible functions of these promoter elements in transcriptional regulation of expression of soybean heat-shock gene are discussed.