Gene expression associated with increased supercooling capability in xylem parenchyma cells of larch (Larix kaempferi).
Gene expression associated with increased supercooling capability in xylem parenchyma cells of larch (Larix kaempferi).
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DOI：
10.1093/jxb/erm223
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发表时间：
2007-10
影响因子：
6.9
通讯作者：
N. Takata;J. Kasuga;D. Takezawa;K. Arakawa;S. Fujikawa
中科院分区：
文献类型：
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作者：
N. Takata;J. Kasuga;D. Takezawa;K. Arakawa;S. Fujikawa
落叶松木质部薄壁细胞通过深过冷适应低温，而皮层薄壁细胞则经历胞外冷冻。XPC的过冷温度极限随季节变化，根据抗寒性测量，夏季为-30摄氏度，冬季为-60摄氏度。对冬季采集的落叶松树枝进行人工脱驯化处理，使其过冷能力从-60℃降至-30℃。为了阐明落叶松XPC过冷能力变化的机制，研究了与过冷能力增强相关的基因表达。通过差异筛选和差异显示分析，发现了30个与XPC过冷能力增强相关的基因。根据它们的功能，这30个基因被分为几类：信号转导因子、代谢酶、胚胎发育晚期丰富蛋白、热休克蛋白、蛋白质合成和染色质构建蛋白、防御反应蛋白、膜转运蛋白、金属结合蛋白和功能未知蛋白。所有这些基因都在冬季表达最丰富，而在夏季表达减少或消失。所有这些基因的表达随着越冬枝条的脱驯化而显著降低或消失。有趣的是，除了一个基因外，所有基因在木质部的表达都比在皮层中表达得更丰富。这30个基因中有11个被认为是新的冷诱导基因。这些结果表明，XPC过冷能力的改变与基因的表达有关，包括功能尚未确定的基因，也表明被认为通过细胞外冷冻在脱水耐受性中发挥作用的基因产物也通过深过冷发挥作用。
Xylem parenchyma cells (XPCs) in larch adapt to subfreezing temperatures by deep supercooling, while cortical parenchyma cells (CPCs) undergo extracellular freezing. The temperature limits of supercooling in XPCs changed seasonally from -30 degrees C during summer to -60 degrees C during winter as measured by freezing resistance. Artificial deacclimation of larch twigs collected in winter reduced the supercooling capability from -60 degrees C to -30 degrees C. As an approach to clarify the mechanisms underlying the change in supercooling capability of larch XPCs, genes expressed in association with increased supercooling capability were examined. By differential screening and differential display analysis, 30 genes were found to be expressed in association with increased supercooling capability in XPCs. These 30 genes were categorized into several groups according to their functions: signal transduction factors, metabolic enzymes, late embryogenesis abundant proteins, heat shock proteins, protein synthesis and chromatin constructed proteins, defence response proteins, membrane transporters, metal-binding proteins, and functionally unknown proteins. All of these genes were expressed most abundantly during winter, and their expression was reduced or disappeared during summer. The expression of all of the genes was significantly reduced or disappeared with deacclimation of winter twigs. Interestingly, all but one of the genes were expressed more abundantly in the xylem than in the cortex. Eleven of the 30 genes were thought to be novel cold-induced genes. The results suggest that change in the supercooling capability of XPCs is associated with expression of genes, including genes whose functions have not been identified, and also indicate that gene products that have been thought to play a role in dehydration tolerance by extracellular freezing also have a function by deep supercooling.