1. Ecotypic variation in chloroplast small heat-shock proteins and related thermotolerance in Chenopodium album.
- Author
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Shakeel S, Haq NU, Heckathorn SA, Hamilton EW, and Luthe DS
- Subjects
- 5' Untranslated Regions, Base Sequence, Chenopodium album genetics, Chloroplasts genetics, Chloroplasts metabolism, Cloning, Molecular, Conserved Sequence, Electron Transport, Gene Expression Regulation, Plant, Heat-Shock Proteins, Small metabolism, Hot Temperature, Hydrophobic and Hydrophilic Interactions, Mississippi, Molecular Sequence Data, New York, Photosystem II Protein Complex metabolism, Plant Proteins genetics, Plant Proteins metabolism, Promoter Regions, Genetic, Protein Isoforms genetics, Protein Isoforms metabolism, Sequence Homology, Amino Acid, Chenopodium album physiology, Heat-Shock Proteins, Small genetics
- Abstract
Production of chloroplast-localized small heat-shock proteins (Cp-sHSP) is correlated with increased thermotolerance in plants. Ecotypic variation in function and expression of Cp-sHSPs was analyzed in two Chenopodium album ecotypes from cool vs. warm-temperate USA habitats [New York (NY) and Mississippi (MS) respectively]. P(et) was more heat tolerant in the MS than the NY ecotype, and MS ecotype derived proportionally greater protection of P(et) by Cp-sHSP during high temperatures. Four genes encoding Cp-sHSPs were isolated and characterized: CaHSP25.99n (NY-1) and CaHSP26.23n (NY-2) from NY ecotype, and CaHSP26.04m (MS-1) and CaHSP26.26m (MS-2) from MS ecotype. The genes were nearly identical in predicted amino-acid sequence and hydrophobicity. Gene expression analysis indicated that MS-1 and MS-2 transcripts were constitutively expressed at low levels at 25 °C, while no NY-1 and NY-2 transcripts were detected at this temperature. Maximum accumulation of NY-1 and NY-2 transcripts occurred at 33 °C and 40 °C for MS-1 and MS-2. Immunoblot analysis revealed that (1) protein expression was highest at 37 °C in both ecotypes, but was greater in MS than NY ecotype at 40 °C; and (2) import of Cp-sHSP into chloroplasts was more heat-labile in NY ecotype. The higher expression of one isoform in MS ecotype may contribute to its enhanced thermotolerance. Absence of correlation between protein and transcript levels, suggests the post-transcriptional regulation is occurring. Promoter analysis of these genes revealed significant variations in heat-shock elements (HSE), core motifs required for heat-shock-factor binding. We propose a correlation between unique promoter architecture, Cp-sHSP expression and thermotolerance in both ecotypes., (Published by Elsevier Masson SAS.)
- Published
- 2011
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