title: Constitutive expression of a small heat-shock protein confers cellular thermotolerance and thermal protection to the photosynthetic apparatus in cyanobacteria.
abstract: The role of a small heat-shock protein (Hsp) in the acquisition of thermotolerance in cyanobacteria was investigated. Synechococcus sp. PCC 7942 was transformed with an expression vector carrying the coding sequence of the hspA gene encoding a small heat-shock protein from Synechococcus vulcanus under the control of the tac promoter. The transformant which was shown to constitutively express HspA displayed improved viability compared with the reference strain upon transfer from 30 to 50 degrees C in the light. When the heat shock was given in darkness, the survival rate in the reference strain increased greatly, approaching a level similar to that for the HspA expressing strain after heat shock in the light. Expression of HspA increased thermal resistance of photosystem II (PS II) and protected phycocyanin from heat-induced photobleaching. Our results are indicative of a central role for HspA in amelioration of the harmful effect of light during heat stress and identified the possible sites of action of the small Hsp in vivo to be the PS II complex and the light-harvesting phycobilisomes.
authors.affiliation: Department of Biochemistry and Molecular Biology, Saitama University, Urawa 338-8570, Japan. nakamoto@post.sitama-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Nakamoto
authors.forename: N
authors.initials: N
authors.lastname: Suzuki
authors.forename: S K
authors.initials: SK
authors.lastname: Roy
mesh_terms: D000222:Adaptation, Physiological; D020418:Algal Proteins / Q000235:genetics* / Q000502:physiology; D002455:Cell Division; D002734:Chlorophyll / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics* / Q000254:growth & development; D004274:DNA, Recombinant / Q000235:genetics; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000502:physiology; D006358:Hot Temperature; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics*; D045524:Phycobilisomes; D013696:Temperature
chemical_list: D020418:Algal Proteins; D004274:DNA, Recombinant; D006360:Heat-Shock Proteins; D045524:Phycobilisomes; D002734:Chlorophyll; D010100:Oxygen