title: Expression of five AtHsp90 genes in Saccharomyces cerevisiae reveals functional differences of AtHsp90s under abiotic stresses.
abstract: The genome of Arabidopsis thaliana contains seven Hsp90 family genes. Three organellar and two cytosolic AtHsp90 isoforms were characterized by functionally expressing them in a temperature-sensitive Hsp90 mutant and a conditional Hsp90-null mutant of Saccharomyces cerevisiae. The cytosolic AtHsp90-1 and AtHsp90-2 showed function similar to that of yeast in chaperoning roles; they could support the growth of yeast mutants at both permissive and non-permissive temperature. Neither the full-length nor mature forms of chloroplast-located AtHsp90-5, mitochondria-located AtHsp90-6 and endoplasmic reticulum (ER)-located AtHsp90-7 could complement the yeast Hsp90 proteins. The cytosolic AtHsp90s could stabilize the biomembrane of the temperature-sensitive Hsp90 mutant strains under stress conditions, while the organellar AtHsp90s could not protect the biomembrane of the temperature-sensitive Hsp90 mutant strains. Yeast two-hybrid results showed that either pre-protein or mature forms of organellar AtHsp90s could interact with cofactors cpHsp70, Hsp70, Hsp70t-2, Cyp40, p23 and a substrate protein of NOS, while cytosolic AtHsp90s could not interact with them. These results suggest that organellar and cytosolic AtHsp90s possibly work through different molecular mechanisms in forming chaperone complexes and performing their functional roles.
authors.affiliation: Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Hongmiao
authors.initials: H
authors.lastname: Song
authors.forename: Pengxiang
authors.initials: P
authors.lastname: Fan
authors.forename: Wuliang
authors.initials: W
authors.lastname: Shi
authors.forename: Rongmin
authors.initials: R
authors.lastname: Zhao
authors.forename: Yinxin
authors.initials: Y
authors.lastname: Li
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins