Deletion analysis of the promoter of Aspergillus oryzae gene encoding heat shock protein 30

In order to find a promoter that could be influenced by temperature shift, we explored and isolated an Aspergillus oryzae gene expressed at high temperatures (37–42 °C) by the cDNA subtraction method. Of the 96 cDNA clones isolated from the subtraction library, one cDNA clone showed 73% identity with Aspergillus nidulans heat shock protein 30 (hsp30). Based on this, we designated the isolated gene hsp30 of A. oryzae. A. oryzae hsp30 was weakly expressed at 30 °C, but strongly at 40 °C. We showed that the promoter of this hsp30 induced heterologous gene expression at high temperatures using β-glucuronidase (GUS) gene as a reporter. Regarding elucidation of the region essential for heat shock response, we showed that the minimum length of the promoter region that was essential for heat shock response was located between − 388 and − 272 (+ 1 indicated the first position of the translation initiation codon) of the hsp30 promoter. This promoter region harbors several putative transcription factor binding sites, including heat shock elements (HSEs), a CCAAT box, and a TATA box. Furthermore, site-directed mutagenesis of this promoter revealed that HSE1 (aTTCgtcGAAacgcccaGAAa) and HSE2 (cGAAagTTCtcGACg), located between − 342 and − 272 of the hsp30 promoter, were its cis-acting elements for heat shock response.