Molecular cloning and expression pattern analyses of heat shock protein 70 genes fromNicotiana tabacum

Abstract

We have isolated three genomic clones that code tobacco HSP70s, using a tobacco hsp70 cDNA clone as a probe.NtHSP70-1, NtHSP70-2, andNtHSP7Q-3 contain full open reading frames of 653, 653, and 648 amino acid residues, respectively. All share three conserved regions, namely the C-terminal substrate binding domain, oligomerization domain, and N-terminal ATPase domain. In a comparison of their amino acid sequences,NtHSP70-1 andNtHSP70-2 were very similar to each other, whileNtHSP70-3 showed significant differences, instead being highly homologous to the cytosolic HSP70 members ofArabidopsis thaliana and other plant species. Therefore,NtHSP70-1 andNtHSP70-3 were chosen for further analyses. RNA blot hybridizations showed typical heat shock-responsive expression patterns, although their signal intensities differed significantly. Transcription ofNtHSP70-1 was also induced by dehydration stress and hormone treatments, such as BA, GA, and IAA, but that ofNtHSP70-3 was not.