Tabaei-Aghdaei S Reza, Pearce Roger S, Harrison Paul
School of Biology, The University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK.
J Exp Bot. 2003 Jun;54(387):1565-75. doi: 10.1093/jxb/erg173. Epub 2003 Apr 28.
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
本研究对胞外糖浓度有助于调节植物细胞冷驯化这一假说进行了验证。利用悬浮培养来控制供给大麦细胞培养物（大麦品种Igri）的培养基中的糖浓度，每天更换培养基以维持该浓度。测定了抗冻性以及应激反应基因blt4.9（编码一种非特异性脂质转移蛋白）和dhn1（编码一种脱水素）的mRNA表达水平。实验中获得的抗冻性和基因表达水平与整株植物冠部冷驯化期间的情况相似。在细胞培养物中，当仅供应1 g l-1蔗糖时，低温（6/2摄氏度）并未诱导抗冻性增加，也未诱导可检测水平的blt4.9或dhn1 mRNA表达增加。然而，处于低温环境且蔗糖浓度较低的培养基中的细胞并非处于糖饥饿状态，这表明这并不能解释细胞在低温环境中生长时未能进行驯化的原因。向在温暖环境（25摄氏度）中生长的细胞供应10 g l-1蔗糖可诱导其对冷冻的驯化以及blt4.9和dhn1 mRNA表达的上调。培养基的渗透压并不能解释这一现象。向在低温或温暖环境中生长的培养物供应30 g l-1蔗糖可诱导更高水平的抗冻性以及blt4.9和dhn1 mRNA表达。结果表明糖参与了冷驯化的调节。
