JXB Advance Access originally published online on April 28, 2003
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Journal of Experimental Botany, Vol. 54, No. 387, pp. 1565-1575,
June 1, 2003
© 2003 Oxford University Press
Sugars regulate cold-induced gene expression and freezing-tolerance in barley cell cultures
Received 19 November 2002; Accepted 19 March 2003
School of Biology, The University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK
1 To whom correspondence should be addressed. Fax: +44 191 222 8684. E-mail: R.S.Pearce{at}ncl.ac.uk
2 Present address: Department of Genetics and Plant Physiology, Research Institute of Forests and Rangelands, PO Box 13185-116, Tehran, Iran.
Abbreviations: EF, elongation factor; nsLTP, non-specific lipid transfer protein; TTC, 2,3,5-triphenyl tetrazolium chloride.
The hypothesis that the extracellular concentration of sugars helps regulate the acclimation of plant cells to cold was tested in this work. Suspension cultures were used to control the concentration of sugars in the medium supplied to barley cell cultures (Hordeum vulgare L. cv. Igri), replacing the medium daily to help maintain the concentration. Freezing tolerance and the levels of mRNA expression of the stress-response genes blt4.9 (coding for a non- specific lipid transfer protein) and dhn1 (coding for a dehydrin) were measured. Similar levels of freezing-tolerance and gene expression were obtained in the experiments as occur during cold-acclimation in the crown of the whole plant. In the cell cultures, cold (6/2 °C) did not induce an increase in freezing tolerance or in the expression of detectable levels of blt4.9 or dhn1 mRNAs when only 1 g l–1 sucrose was supplied. However, the cells in this low sucrose medium in the cold were not sugar-starved, indicating that this did not explain the failure of the cells to acclimate when grown in the cold environment. Ten g l–1 sucrose supplied to cells grown in the warm (25 °C) induced acclimation to freezing and up-regulation of expression of blt4.9 and dhn1 mRNAs. Osmolality of the medium did not explain this. Thirty g l–1 sucrose induced yet higher levels of freezing tolerance and of blt4.9 and dhn1 mRNAs in cultures grown in either the cold or the warm environment. The results implicate sugars in the regulation of cold acclimation
Key words: Cold-acclimation, freezing-tolerance, gene expression, Hordeum, sugars.
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