Expression analysis and functional characterization of a novel cold-responsive gene <Emphasis Type="Italic">CbCOR15a</Emphasis> from <Emphasis Type="Italic">Capsella bursa</Emphasis>-<Emphasis Type="Italic">pastoris</Emphasis>

The cold-responsive (COR) genes involved in C-repeat binding factor signaling pathway function essentially in cold acclimation of higher plants. A novel COR gene CbCOR15a from shepherd’s purse (Capsella bursa-pastoris) was predicted to be a homolog of COR15 in Arabidopsis. The analysis of tissue specific expression pattern as well as characterization of the CbCOR15a promoter revealed that the expression of CbCOR15a was induced by coldness not only in leaves and stem but also in roots. Sequence analysis showed that a 909 bp promoter region of CbCOR15a contained two CRT/DRE elements, two ABRE elements, one auxin-responsive TGA-element and one MeJA-responsive CGTCA-motif. In young seedlings the expression of CbCOR15a could be apparently increased by SA, ABA, MeJA and IAA, and transiently increased by GA₃ accompanied by obvious feedback suppression. According to the altered physiological index values in tobacco under cold treatments, the overexpression of CbCOR15a significantly increased the cold tolerance of transgenic tobacco plants. It can be suggested that CbCOR15a was involved in cold response of Capsella bursa-pastoris associated with SA, ABA, MeJA, IAA and GA₃ regulation and confers enhanced cold acclimation in transgenic plants.     

& 转录因子CBF在植物抗寒中的重要作用

低温能够诱导植物许多基因的表达,从而使植物具有抗寒性,这种现象称为冷驯化。对于植物冷驯化的分子机理,目前研究的最多的是CBF转录因子调控的信号转导途径,其作用途径可归纳为：CBF(C-repeat Binding Factor)转录因子→CRT/DRE(C-repeat /Dehydration Responsive Element)基序→COR基因表达→植物抗寒性增加。研究CBF转录因子在抗寒中的作用机制,能为提高植物的抗寒性,培育抗寒作物品种提供新方向。      

植物冷驯化相关基因研究进展

摘要 冷驯化是与提高植物抗冷性有关的生物化学及生理学过程, 主要包括寒驯化(cool acclimation)和冻驯化(freezing acdimation)。在冷驯化过程中, 植物体内许多基因在转录水平上的表达受到影响, 已经克隆了大量的相关基因,它们组成复杂的分子调控网络。目前研究表明不依赖ABA的低温信号转导途径是植物冷驯化机制的重要组成部分, 其中CBF/DREB1是该调控过程的关键转录因子, 与植物通过冷驯化而提高冰冻耐受能力密切相关。进一步利用转基因技术, 可有效地改善作物的耐冷性状。     

植物冷驯化相关基因研究进展

冷驯化是与提高植物抗冷性有关的生物化学及生理学过程,主要包括寒驯化（cool acclimation）和冻驯化（freezing acdimation）。在冷驯化过程中,植物体内许多基因在转录水平上的表达受到影响,已经克隆了大量的相关基因,它们组成复杂的分子调控网络。目前研究表明不依赖ABA的低温信号转导途径是植物冷驯化机制的重要组成部分,其中CBF/DREB1是该调控过程的关键转录因子,与植物通过冷驯化而提高冰冻耐受能力密切相关。进一步利用转基因技术,可以有效地改善作物的耐冷性状。     

拟南芥CBF1与植物对低温和干旱的抗性

对冷驯化过程中基因表达差异的认识,使抗冻基因(COR)的克隆及其功能的分析成为研究冷驯化过程的主要目标。在拟南芥和其他抗冻植物中,分离了许多COR基因,这些基因对植物抗冻起着非常重要的作用。在拟南芥COR调控的研究中,发现了CBF转录因子的基因家族,其中CBF1能调控一组COR基因的表达。近年来,在冷敏植物如番茄和玉米中也发现了CBF类似基因,拟南芥CBF1基因在转基因番茄中的过量表达提高了植株的抗寒和抗旱性。这一研究结果展示了拟南芥CBF1类似基因的应用可能为冷敏植物抗寒和抗旱性的品种改良提供一条新的途径。     

Clinal variation in the non-acclimated and cold-acclimated freezing tolerance of Arabidopsis thaliana accessions

Arabidopsis thaliana is a geographically widely spread species consisting of local accessions differing both genetically and phenotypically. These differences may constitute environmental adaptations and a latitudinal cline in freezing tolerance has been shown previously. Many plants, including Arabidopsis, exhibit increased freezing tolerance after cold exposure (cold acclimation). Here we present evidence for geographical clines (both latitudinal and longitudinal) in acclimated (ACC) and non-acclimated (NA) freezing tolerance, estimated from electrolyte leakage measurements on 54 accessions. Leaf Pro contents were not correlated with freezing tolerance, while sugar contents (Glc, Fru, Suc, Raf) were in the ACC, but not the NA state. Expression levels of 14 cold-induced genes were investigated before and after 2 weeks of cold acclimation by quantitative RT-PCR. Expression of the CBF1, 2 and 3 genes was not correlated with freezing tolerance. The expression of some CBF-regulated (COR) genes, however, was correlated specifically with ACC freezing tolerance. A tight correlation between CBF and COR gene expression was only observed under non-acclimating conditions, where CBF and COR expression were also correlated with the expression of PRR5, a component of the circadian clock. Collectively, this study sheds new light on the molecular determinants of plant-freezing tolerance and cold acclimation and their geographical dependence.