Ecotypic variation in chloroplast small heat-shock proteins and related thermotolerance in Chenopodium album

Samina Shakeel, Noor Ul Haq, Scott A. Heckathorn, E. William Hamilton, Dawn S. Luthe

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26 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)898-908
Number of pages11
JournalPlant Physiology and Biochemistry
Issue number8
StatePublished - Aug 2011

All Science Journal Classification (ASJC) codes

  • Physiology
  • Genetics
  • Plant Science


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