Journal Article

The Effects of Cold Acclimation on Photosynthetic Apparatus and the Expression of <i>COR14b</i> in Four Genotypes of Barley (<i>Hordeum vulgare</i>) Contrasting in their Tolerance to Freezing and High-light Treatment in Cold Conditions

Marcin Rapacz, Barbara Wolanin, Katarzyna Hura and MirosŁaw Tyrka

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 101, issue 5, pages 689-699
Published in print April 2008 | ISSN: 0305-7364
Published online February 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn008
The Effects of Cold Acclimation on Photosynthetic Apparatus and the Expression of COR14b in Four Genotypes of Barley (Hordeum vulgare) Contrasting in their Tolerance to Freezing and High-light Treatment in Cold Conditions

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Cold acclimation modifies the balance of the energy absorbed and metabolized in the dark processes of photosynthesis, which may affect the expression of cold-regulated (COR) genes. At the same time, a gradual acclimation to the relatively high light conditions is observed, thereby minimizing the potential for photo-oxidative damage. As a result, the resistance to photoinhibition in the cold has often been identified as a trait closely related to freezing tolerance. Using four barley genotypes that differentially express both traits, the effect of cold acclimation on freezing tolerance and high-light tolerance was studied together with the expression of COR14b, one of the best-characterized barley COR genes.

Methods

Plants were cold acclimated for 2 weeks at 2 °C. Freezing tolerance was studied by means of electrolyte leakage. Changes in photosynthetic apparatus and high-light tolerance were monitored by means of chlorophyll fluorescence. Accumulation of COR14b and some proteins important in photosynthetic acclimation to cold were studied with western analysis. COR14b transcript accumulation during cold acclimation was assessed with real-time PCR.

Key Results

Cold acclimation increased both freezing tolerance and high-light tolerance, especially when plants were treated with high light after non-lethal freezing. In all plants, cold acclimation triggered the increase in photosynthetic capacity during high-light treatment. In two plants that were characterized by higher high-light tolerance but lower freezing tolerance, higher accumulation of COR14b transcript and protein was observed after 7 d and 14 d of cold acclimation, while a higher transient induction of COR14b expression was observed in freezing-tolerant plants during the first day of cold acclimation. High-light tolerant plants were also characterized with a higher level of PsbS accumulation and more efficient dissipation of excess light energy.

Conclusions

Accumulation of COR14b in barley seems to be important for resistance to combined freezing and high-light tolerance, but not for freezing tolerance per se.

Keywords: Chlorophyll a fluorescence; cold acclimation; COR14b; non-photochemical energy quenching; freezing tolerance; gene expression; Hordeum vulgare; photoinhibition; photosynthetic acclimation to cold; photosynthetic capacity

Journal Article.  7743 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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