低温胁迫限制了许多野生植物和作物的地理分布，降低了生产率。植物在低温胁迫下生存能力差别很大，来源于热带和亚热带的冷敏感植物在温度高于冰点的低温条件下会发生不可逆的伤害，而温带地区的植物能够承受极端的冰冻条件。近年来有关冷敏感植物和温带植物低温胁迫下生理生化响应特征，转录组学、蛋白质组学和代谢组学分析取得了较快进展，从不同层次阐明了木本植物调节低温反应和抗冷(冻)性的生理和分子机制，为利用抗冷(冻)相关基因进行林木抗(冷)冻分子育种提供了重要参考。冷敏感树木在1～10℃的低温胁迫下，会出现水分状况、矿质营养、光合作用、呼吸作用和新陈代谢等生理过程的紊乱，造成冷害甚至死亡。钙信号途径是低温应答过程中重要的信号转导途径。ABA 通过 ABA 依赖的转录因子的转录激活参与植物胁迫响应基因的调节。低温响应转录调控分为 CBF 途径和非 CBF 途径。CBF 调控下游基因的表达过程：植物细胞膜相关受体首先感知环境信号并传送到细胞核，通过 Ca2+和 MAPKs 等感知和传导信号，诱导转录因子 CBF 的表达，从而激活冷响应基因的启动子，触发冷响应机制(基因激活)，转录的mRNA 被翻译成不同的蛋白质。这些基因产物参与改变膜质成分组成、抗氧化酶活性、渗透物质含量等生理过程，从而提高抗冷性。另外，CBF 基因表达也受到上游一些转录因子的调节，包括钙离子信号途径和 ICE1－CBF －寒冷响应途径。树木抗冷锻炼和抗冻锻炼的机制与代谢途径有许多相似之处，但后者可能更复杂，因为它需要面对极端的低温和不正常的温度波动。抗冻锻炼期间低温诱导的抗冻蛋白具有较强的抑制冰晶重结晶的活性；脱水蛋白和胚胎后期丰富蛋白( LEA)通过渗透调节保护细胞；热休克蛋白( HSPs)调节蛋白质的折叠和运输，恢复钝化酶的活性；抗氧化酶系统清除氧自由基和过氧化氢；早期光诱导蛋白参与高光胁迫适应过程，这些蛋白在树木抗冻机制中具有重要作用。在树木抗冷(冻)领域，未来应加强对控制抗冷(冻)生理变化的转录因子及关键功能基因的全面解析，深入探讨光、温度等环境信号诱导抗冻性形成机制，使用蛋白质组学方法与其他技术相结合阐明低温胁迫下重要蛋白质表达机制和功能，完整地揭示木本植物在低温逆境下的生存机制。%Low temperature stress limits the geographical distribution of many wild plant and crops,and reduces their productivity. There are huge differences in survivability of trees to low temperature stress. Chilling sensitive trees from tropics and subtropics are irreversibly damaged at temperature condition higher than freezing point,while those species originated from temperate-zone can withstand extreme freezing conditions. In recent years,the analyses of physiological and biochemical response characteristics, transcriptome, proteome and metabolome of chilling sensitive trees and temperate-zone trees under low temperature stress have been rapidly developed,which from various levels have elucidated the physiological and molecular mechanisms that woody plant regulating low-temperature response and freezing tolerance. These analyses provide important reference for molecular breeding of freezing-tolerant woody plant by using anti-freezing related genes. Under the low temperature stress of 1—10 ℃,chilling sensitive trees would appear disorders physiological processes in water status,mineral nutrition,photosynthesis,respiration and metabolism,and hence lead to chilling damage,and even death. Calcium signal transduction pathway is the important signal transduction pathway during low temperature response process. ABA is involved in the regulation of plant stress response gene by transcriptional activation of ABA-dependent transcription factor. Regulation of low temperature response transcription can be divided into CBF pathway and non-CBF pathway. CBF regulates the expression processes of downstream target genes: related receptors of plant cell membrane first perceive environmental signal and transmit it to cell nucleus. The signal is perceived and transducted through Ca2 + and MAPK and induces expression of CBF,which will activate the promoter of cold-response gene and trigger cold response mechanism ( gene activation ) , and the transcribed mRNA is translated into various proteins. These gene products participate in physiological processes of changing the composition of membrane,antioxidant enzyme activities,content of osmotic substances,which will improve cold resistance. On the other hand,CBF gene expression is also regulated by some upstream transcriptional factors,including Ca2 + signal way and ICE1-CBF cold response way. Mechanism and metabolic pathway of chilling acclimation in trees are much similar to freezing acclimation in trees,but the latter may be more complicated,because it needs to face extreme and abnormal temperature variance. The antifreeze protein induced by cold during freezing acclimation has strong activity to inhibit ice recrystallization;Dehydrin and LEA protein protect cellular by osmoregulation; Heat shock protein ( HSP ) regulates protein folding and transportation,and restores activity of modifying enzyme; antioxidant enzyme system scavenges oxygen free radical and hydrogen peroxide; early light-induced protein ( ELIP ) takes parts in the high light stress acclimation process,which plays important roles for antifreeze mechanism of trees. In the field of tree's freezing tolerance,comprehensive analysis of the transcriptional factor and functional genes shall be emphasized in the future; the development mechanism of freezing tolerance induced by environmental signal such as light,temperature,etc. shall be more thoroughly study; expression mechanism and function of important proteins under low temperature stress shall be explained by combination of proteomics methods and other technology to integrally reveal the surviving mechanism of woody plants under low temperature stress.
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