Induction of Hsp70 in the fungus Rhizopus nigricans

We characterised two positive clones, RnH20/2 and RnH2/3, isolated from the cDNA library prepared from the fungus Rhizopus nigricans previously expose d to heat shock. Nucleotide sequences of both cDNA clones contained open re ading frames for polypeptides with a significant amino acid identity to eac h other and to cytoplasmic members of Hsp70s from different eukaryotic orga nisms. Northern blot analysis, using a fragment of RnH2/3 as a probe, revea led that in the fungus R. nigricans the Hsp70 transcripts were inducible wi th deoxycorticosterone and testosterone as well as with heat stress, ethano l, CuSO4, and H2O2. This is the first report on isolation of cDNAs encoding Hsp70s from the fungal phylum Zygomycota. (C) 1999 Academic Press.