title: Interplay between heat shock proteins HSP101 and HSA32 prolongs heat acclimation memory posttranscriptionally in Arabidopsis.
abstract: Heat acclimation improves the tolerance of organisms to severe heat stress. Our previous work showed that in Arabidopsis (Arabidopsis thaliana), the "memory" of heat acclimation treatment decayed faster in the absence of the heat-stress-associated 32-kD protein HSA32, a heat-induced protein predominantly found in plants. The HSA32 null mutant attains normal short-term acquired thermotolerance but is defective in long-term acquired thermotolerance. To further explore this phenomenon, we isolated Arabidopsis defective in long-term acquired thermotolerance (dlt) mutants using a forward genetic screen. Two recessive missense alleles, dlt1-1 and dlt1-2, encode the molecular chaperone heat shock protein101 (HSP101). Results of immunoblot analyses suggest that HSP101 enhances the translation of HSA32 during recovery after heat treatment, and in turn, HSA32 retards the decay of HSP101. The dlt1-1 mutation has little effect on HSP101 chaperone activity and thermotolerance function but compromises the regulation of HSA32. In contrast, dlt1-2 impairs the chaperone activity and thermotolerance function of HSP101 but not the regulation of HSA32. These results suggest that HSP101 has a dual function, which could be decoupled by the mutations. Pulse-chase analysis showed that HSP101 degraded faster in the absence of HSA32. The autophagic proteolysis inhibitor E-64d, but not the proteasome inhibitor MG132, inhibited the degradation of HSP101. Ectopic expression of HSA32 confirmed its effect on the decay of HSP101 at the posttranscriptional level and showed that HSA32 was not sufficient to confer long-term acquired thermotolerance when the HSP101 level was low. Taken together, we propose that a positive feedback loop between HSP101 and HSA32 at the protein level is a novel mechanism for prolonging the memory of heat acclimation.
authors: Department of Biochemical Sciences and Technology, National Taiwan University, Taipei 10617, Taiwan, Republic of China.
authors: Ting-ying
authors: TY
authors: Wu
authors: Yu-ting
authors: YT
authors: Juan
authors: Yang-hsin
authors: YH
authors: Hsu
authors: Sze-hsien
authors: SH
authors: Wu
authors: Hsiu-ting
authors: HT
authors: Liao
authors: Raymond W M
authors: RW
authors: Fung
authors: Yee-yung
authors: YY
authors: Charng
mesh_terms: D000064:Acclimatization / Q000187:drug effects / Q000235:genetics*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D003433:Crosses, Genetic; D003513:Cycloheximide / Q000494:pharmacology; D004843:Epistasis, Genetic / Q000187:drug effects; D005020:Ethyl Methanesulfonate; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005816:Genetic Complementation Test; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D020125:Mutation, Missense / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: C568306:(3-ethoxycarbonyloxirane-2-carbonyl)leucine (3-methylbutyl) amide; D029681:Arabidopsis Proteins; C115569:HSP101 protein, plant; D006360:Heat-Shock Proteins; C511729:Hsa32 protein, Arabidopsis; D010940:Plant Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D003513:Cycloheximide; D005020:Ethyl Methanesulfonate; D008156:Luciferases; D007930:Leucine