Plants contain a novel multi-member class of heat shock factors without transcriptional activator potential.

摘要: Based on phylogeny of DNA-binding domains and the organization hydrophobic repeats, two families heat shock transcription factors (HSFs) exist in plants. Class A HSFs are involved activation response, but role class B is not clear. When transcriptional activities full-length were monitored tobacco protoplasts, no from soybean or Arabidopsis showed activity under control stress conditions. Additional assays confirmed finding that lacked capacity to activate transcription. Fusion a heterologous domain human HSF1 (AD2) C-terminus GmHSFB1-34 gave evidence synergistic enhancement AD2 activity, which would be expected if weak present. Furthermore, AtHSFB1-4 (class B) was rescued by coexpression with AtHSFA4-21 A) indicating HSF able provide missing function required for activity. The potential mapped primarily 39 amino acid fragment enriched bulky acidic residues. Deletion mutagenesis C-terminal activator regions tomato indicated these plant lack heat-inducible regulatory analogous those mammalian HSF1. These findings suggest regulation plants may differ metazoans partitioning negative positive functional onto separate proteins. responsible stress-inducible genes whereas some inert specialized repression, down-regulation, response.