Sugars regulate cold-induced gene expression and freezing-tolerance in barley cell cultures

Abstract

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 degrees 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 degrees 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

The Gentio-Oligosaccharide Gentiobiose Functions in the Modulation of Bud Dormancy in the Herbaceous PerennialGentiana

“…This observation is consistent with sugar accumulation in the crown buds of leafy spurge (Anderson et al, 2005). Sucrose is believed to serve as a protectant against cold and freezing stresses in many plants (Tabaei-Aghdaei et al, 2003;Rekarte-Cowie et al, 2008). Furthermore, the accumulation of raffinose, a nonreducing oligosaccharide containing fructose, improves drought and cold stress tolerance in Arabidopsis (Taji et al, 2002).…”

Physiological and molecular changes in plants grown at low temperatures

“…The oligosaccharides raffinose and stachyose are especially associated with cold hardiness, low temperature and dormancy (Aït Barka and Audran 1996;Couee et al 2006). Moreover, the concentration of sucrose, the most easily detectable sugar in cold-tolerant species, increases several fold during exposure to LT (Bohnert and Sheveleva 1998;Tabaei-Aghdaei et al 2003). The accumulation of sucrose in cane sugar exposed to salt stress or to LT stress supports the role of this sugar as an osmoprotectant that stabilizes cellular membranes and maintains turgor (Jouve et al 2004).…”

Comparative studies on tolerance of Medicago truncatula and Medicago falcata to freezing

“…For instance, the reduced accumulation of sucrose and glucose in an Arabidopsis mutant than in wild-type during cold acclimation renders the mutant sfr4 more sensitive to freezing (Uemura et al 2003). Exogenous supply of sugars enhances freezing tolerance in a number of species (Tabaei-Aghdaei et al 2003). During cold acclimation, the accumulation of sucrose is related to increases in activities of SPS and SuSy, while sucrose content is negatively regulated by the activity of acid invertase (Gutierrez-Miceli et al 2002;Bhowmik et al 2006).…”

“…During cold acclimation, the accumulation of sucrose is related to increases in activities of SPS and SuSy, while sucrose content is negatively regulated by the activity of acid invertase (Gutierrez-Miceli et al 2002;Bhowmik et al 2006). In addition, sugars such as sucrose and glucose may also play a role in regulation of cold-induced expression of genes in plants (Tabaei-Aghdaei et al 2003). Moreover, there are reports demonstrating that raffinose and stachyose levels in the crown are positively correlated with freezing tolerance in alfalfa (Medicago sativa) (Castonguay et al 1995).…”