Isolation, partial length sequence and expression of steroid inducible hps 70 gene from Rhizopus nigricans

Previous studies have shown that filamentous fungus Rhizopus nigricans responds to addition of different steroids into growth medium with induction of hydroxylation system and that some steroids provoke stress response. The purpose of this study was to investigate whether those steroids provoke induction of Hsp70 gene(s), well studied markers of stress response in different cells and organisms. The expression studies of fungal Hsp70 gene(s) using Northern blot analysis showed that fungal hsp70 mRNA was upregulated after treatment of mycelia with deoxycorticosterone and testosterone, but not after exposure to progesterone. In addition, expression of fungal Hsp70 mRNA was elevated after exposure of mycelia to heat shock (32°C), ethanol, heavy metal (CuSO₄), and oxidative stressor (H₂O₂), whereas treatment of mycelia with osmotic stressor (KCl) didn't have any influence on stress protein expression. The partial nucleotide sequence and deduced amino acid sequence homology search revealed that the cDNA clone (λ hs20/2), isolated from cDNA library prepared from heat shock treated fungal mycelia, contained Hsp70 gene of DnaK subfamily.