杨树抗冻性的研究现状

杨树是世界上广泛栽培的重要造林树种之一,我国是世界上杨树资源丰富的国家,杨树具有速生丰产、实用性强、无性繁殖能力强,且基因组较小等特点,现已成为研究林木生理和基因工程研究的模式植物。本文概述了国内外有关杨树抗冻性的生理生化性质及其指标、天然杂种的选择以及人工杂交选育种等方面研究现状,并展望了杨树基因工程在杨树抗冻性遗传改良中的应用前景,此外,对信后如何开展杨树抗冻改良育种的研究提出了一些设想。     

杨树叶锈病研究

松杨栅锈菌（Melampsora larici-populina）导致的杨树叶锈病是杨树病害中分布最广、危害最大的一种病害,它造成杨树林的材积损失和材质下降,严重制约着杨树商品林和生态林的发展。该文从病原菌的分布和寄主种类、病原菌生理分化、寄主抗锈性及分子标记、防治措施等几方面介绍了杨树叶锈病的研究。     

植物抗冻机理研究新进展：抗冻基因表达及其功能

综述了迄今业已分离和鉴定的低温诱导表达的抗冻基因,以及通过染色体基因制图方法揭示和证实的抗冻性基因。并着重地介绍了这些抗冻基因在提高植物抗冻能力上的功能。这些抗冻基因表达合成的新多肽具有高度的亲水性,起着保护和稳定细胞膜结构的作用,从而防止冰冻伤害、提高植物的抗冻能力。同时还介绍了抗冻基因表达中的某些调节因子,其中尤其值得注意的是,CBF基因似乎有可能作为抗冻基因表达的“主开关”,以及Ca2+作为植物细胞的第二信使在传递低温信号、启动和调节抗冻基因表达中可能的重要作用。这些研究结果,不仅为阐明植物的抗冻机理提供了新的证据,而且为改良农作物的抗寒性提供了新的启示。     

植物抗冻机理研究新进展：抗冻基因表达及其功能

综述了迄今业已分离和鉴定的低温诱导表达的抗冻基因,以及通过染色体基因制图方法褐示和证实的抗冻性基因,并着重地介绍了这些抗冻基因在提高植物抗冻能力上的功能。这些抗冻基因表达合成的新多肽具3有高度的亲水性,起着保护和稳定细胞膜结构的作用,从而防止冰冻伤害,提高植物的抗冻能力,同时还介绍了抗冻基因表达中的某些调节因子,其中尤其值得注意的是,CBF基因似乎有可能作为抗冻基因表达的“主开关”,以及Ca^2 作为植物细胞的第二信使在传递低温信号,启动和调节抗冻基因表达中可能的重要作用,这些研究结果,不仅为阐明植物的抗冻机理提供了新的证据,而且为改良农作物的抗寒性提供了新的启示。     

植物抗冻基因工程研究进展

提高作物的抗冻性对于提高作物产量有着非常重要的意义。目前,对冷诱导基因、CBF、ICE、抗冻蛋白基因、脂肪酸去饱和酶基因、脯氨酸基因、SOD基因与抗冻的关系进行了广泛的研究,研究表明对这些抗冻相关基因进行转基因,可以提高植物的抗冻性。而一些抗冻基因应用到作物上,也可以提高作物的抗冻性。     

杨属（PopulusL.）种质资源遗传学评价研究进展

杨属（PopulusL.）种质资源极其丰富,为了有效保存、合理利用杨属种质资源,国内外开展了大量的种质资源遗传学评价研究。该文在介绍杨树系统分类的基础上,概述了白杨派、青杨派和黑杨派等在生物学特性、抗性（耐盐、抗旱、抗冻及抗病虫）、适应性及DNA遗传多态性等方面的遗传学评价研究进展,重点讨论了杨树种质资源评价研究中存在的问题和不足,并对其研究前景进行了展望。     

紫菜抗逆境生理与调控机制研究进展

逆境胁迫生理是当前植物生理学研究的热点领域。作为世界上重要的经济海藻之一,紫菜养殖量逐年增加。但是由于紫菜主要生长于潮间带或者低潮带区域,海水环境中各种非生物胁迫是影响紫菜产量的重要威胁。近年来,随着m RNA差异显示、抑制消减杂交、c DNA代表性差异分析等技术的发展,国内外学者围绕紫菜抗逆生理的基因调控机制展开了一系列的研究,取得一定的科学认知。本文综述了紫菜在高低温、干出、光照、营养盐与重金属等胁迫因子影响下的生理生化特征及其抗逆调控机制等方面的主要研究进展,提出了研究展望。本研究拟为今后改良紫菜抗逆性的遗传育种工作提供参考。     

黄盖蝶抗冻蛋白的分离与cDNA克隆

五十年代末,六十年代初,国外学者从极地鱼类中 发现并分离出能使血液冰点降低的抗冻物质。这种物 质分为塘蛋白及抗冻肤两类。人们以美洲拟蝶(Pseudopleuronecscs americanus）等为材料,对抗冻肚的性 质、一级结构、mRNA,基因表达等都进行了研究。 有关抗冻肤的作用机理以及基因的表达调节都是学者 注意的中心。对抗冻蛋白基因的研究,在理论上可以 使人们了解鱼类血清冰点降低的遗传基础,研究基因 表达的调节等基础问题,另一方面也可为用遗传工程 手段改良经济鱼类品种,提高鱼类抗冻能力作一些贡 献。但国内这方面的工作起步较晚,目前尚少有类似 的工作报道。     

杨属(Populus L.)种质资源遗传学评价研究进展

杨属(Populus L.)种质资源极其丰富, 为了有效保存、合理利用杨属种质资源, 国内外开展了大量的种质资源遗传学评价研究。该文在介绍杨树系统分类的基础上, 概述了白杨派、青杨派和黑杨派等在生物学特性、抗性(耐盐、抗旱、抗冻及抗病虫)、适应性及DNA遗传多态性等方面的遗传学评价研究进展, 重点讨论了杨树种质资源评价研究中存在的问题和不足, 并对其研究前景进行了展望。     

中国杨树人工林培育技术研究进展

我国杨树人工林总面积达700万hm²,位居世界第一.发展杨树人工林、满足社会经济发展和环境保护的需要是世界杨树研究的发展趋势.在介绍中国杨树栽培区区划、杨树人工林的主要栽培无性系及其生产力的基础上,总结了近10年来我国杨树在立地质量评价、苗木培育技术、人工林定向培育模式、混交林营造技术、林农复合经营技术、人工林水分和养分管理技术、立地生产力维护和杨树人工林的生态功能等方面的研究进展,讨论了我国杨树人工林的生产潜力、杨树人工林的布局、杨树人工林定向培育及加强杨树人工林的环境功能研究等问题,为我国杨树人工林资源的培育及可持续经营提供参考.     

Progress in the Study of Molecular Genetic Improvements of Poplar in China

The poplar is one of the most economically important and intensively studied tree species owing to its wide application in the timber industry and as a model material for the study of woody plants. The natural resource of poplars in China is replete. Over the past 10 years, the application of molecular biological techniques to genetic improvements in poplar species has been widely studied in China. Recent advances in molecular genetic improvements of poplar, including cDNA library construction, gene cloning and identification, genetic engineering, gene expression, genetic linkage map construction, mapping of quantitative trait loci （QTL） and molecular-assisted selection, are reviewed in the present paper. In addition, the application of modern biotechnology to molecular improvements in the genetic traits of the poplar and some unsolved problems are discussed.     

Complex patterns of hybridization between exotic and native North American poplar species

? Premise of the study: Poplars and their hybrids are seen as important candidates for bioenergy initiatives. However, many concerns have been raised about large-scale plantations of new poplar cultivars. The deployment of such plants with novel traits brings the risk of potential spread of novel genome regions (including exotic genes, transgenes, or other heritable modifications) into natural populations of related species. The possibility of introgression is especially high in poplars because reproductive barriers between species are weak. Knowledge of the frequency of hybridization between cultivated trees and natural populations is one important step in the risk-assessment process. ? Methods: We studied the rate of spontaneous hybridization from two sexually mature poplar plantations into adjacent natural populations of Populus deltoides and P. balsamifera. The two plantations, both in eastern Canada, contain many different complex hybrid clones with components from exotic species, mostly P. nigra, P. trichocarpa, and P. maximowiczii. We analyzed 12 species-specific single nucleotide polymorphisms from six different genes in 5373 offspring sampled from the natural populations. ? Results: Contributions from all three exotics were found in the offspring, confirming low reproductive barriers among poplar species in these sections. The frequency of hybrid offspring varied among pollen donors, recipient populations, and years. ? Conclusions: The remarkably high rate of hybridization that was found in the smallest natural population sampled suggests that small peripheral populations carry a higher risk of introgression. These results could be used as a starting point for developing regulatory guidelines for the introduction of plants with novel traits.     

The relationship between isoprene emission, CO(2) assimilation and water use efficiency across a range of poplar genotypes

Poplars (Populus sp.) are among the strongest isoprene (Iso)-emitting plants. Ten poplar genotypes belonging to four different species were grown under the same environmental conditions in a common garden experiment, to study the influence of the genetic variability on Iso emission and on the relationship between Iso and photosynthesis. Photosynthesis ranged from 13 to 20 μmol CO(2) m(-2) s(-1) , whereas Iso emission ranged from 18.2 to 45.2 nmol m(-2) s(-1) . There was no clear association between Iso emission and photosynthesis. In most genotypes, photosynthetic capacity developed earlier than Iso emission capacity. The emission of Iso was inversely correlated with the intercellular CO(2) concentration (C(i) ) and positively correlated with instantaneous water use efficiency. It is speculated that, by regulating C(i) , stomatal opening also indirectly controls Iso emission in poplars. A positive linear correlation between the fraction of recently assimilated carbon emitted as Iso and Iso emission rate was found. The slope of this relationship indicated that each nanomole of Iso emitted requires a fixed fraction of photosynthetic carbon regardless of the intra- and interspecific variability in the Populus genus, and of leaf ontogeny. A comparison with data from recent studies showed that the slope of this relationship increases in drought-stressed leaves. However, this might be explained by an increasing contribution of carbon sources for Iso biosynthesis from stored photosynthates. If this is true, then the amount of carbon directly shunted from photosynthesis into Iso is constant in all poplars and is not influenced by abiotic stresses.     

意杨苗木耗水特征与水分利用效率

研究杨树耗水量的变化特征、水分利用效率及其影响因子对杨树生理生态研究、造林树种的选择和林业生态工程建设具有重要的指导价值。以意杨(Populus euramevicana cv.‘I-214’)为研究对象进行盆栽试验,设定了4个处理组,分别为T1处理组(种植意杨,密封处理),T2处理组(种植意杨,非密封处理),T3处理组(不种植意杨,非密封处理),C处理组(不种植意杨,密封处理),定量分析了意杨耗水规律、水分利用效率及土壤蒸发量与植株生理特性、气象环境因子之间的关系。结果表明:(1)4个处理组耗水量变化曲线均呈"单峰型",且在7月份达到最大值,2月份降到最低值。(2)栽植意杨的土壤水分蒸发量占总耗水量的15.9%,全年波动状态稳定,本底流失量占30.4%。(3)在地表覆盖物下的意杨蒸腾耗水量占总耗水量的53.7%,年变化曲线为单峰型;栽培意杨的土壤水分总流失量是不栽培意杨土壤总流失量2.77倍;在裸地上种植意杨的土壤水分总蒸发量仅比没有意杨的裸地土壤多流失7.9%水分。(4)在有地表覆盖物下和裸地上的意杨叶面平均蒸腾强度分别为30.8 g cm~(-2)a~(-1),9.5 g cm~(-2)a~(-1);平均每克生物量耗水量为39.61 g。综上所述,意杨具有很强的蒸腾耗水能力,种植意杨可能会造成造林地区土壤水分大量流失,使该地区深层土壤干燥化,不利于土壤储水调节作用的发挥。     

Enabling inverse metabolic engineering through genomics

Inverse metabolic engineering (IME) is a powerful framework for engineering cellular phenotypes. Progress in this field has been limited by a lack of comprehensive methods for efficiently identifying the genetic basis of relevant phenotypes. Advances in genomics technologies, including DNA microarrays and gene sequencing, have dramatically improved our ability to relate changes in phenotype with associated changes in genotype. When applied in the context of IME, these tools should enable the integration of "evolutionary" and "direct" approaches to engineering cell physiology, which should improve our understanding of the complex interactions affecting the expression, evolution and engineering of traits in natural and industrial hosts.     

Genetic Modification of Short Rotation Popular Wood: Properties for Ethanol Fuel and Fiber Productions

Opportunities for matching wood chemical and physical properties to manufacturing and product requirements via genetic modification have long been recognized. Exploitation is now feasible due to advances in trait measurement, breeding, genetic mapping and marker, and genetic transformation technologies. With respect to classic selection and breeding of short-rotation poplars, genetic parameters are favorable for decreasing lignin content and increasing specific gravity, but less so for increasing cellulose content. Knowledge of functional genomics is expanding, as is that needed for eventual application of marker-aided breeding, trait dissection, candidate gene identification, and gene isolation. Research on gene transfer has yielded transgenic poplars with decreased lignin and increased cellulose contents, but otherwise normal growth and development. Until effective marker-aided breeding technologies become available, the most promising approach for enhancing ethanol fuel and fiber production and processing efficiencies centers on selecting and breeding poplars for high wood substance yields and genetically transforming them for decreased lignin and increased cellulose contents.     

Responses to cadmium in leaves of transformed poplars overexpressing Γ-glutamylcysteine synthetase

Poplars overexpressing a bacterial Γ -glutamylcysteine synthetase ( Γ -ECS) in the cytosol (lines ggs11 and ggs28) had a 30-fold increase in foliar Γ -ECS activity relative to untransformed controls. Foliar Γ -glutamylcysteine ( Γ -EC) was increased by 10-fold while foliar glutathione accumulation increased by up to 3.5-fold in the leaves of the transformants. Untransformed and transformed poplars were grown with different soil concentrations of cadmium (0–1100 μg g⁻¹ soil) for 2 weeks. Cadmium accumulated in the leaves of both transformed and untransformed poplars and growth was inhibited. Growth inhibition and foliar cadmium accumulation were greatest at the highest soil cadmium concentrations in all lines. Exposure to cadmium enhanced the foliar cysteine, Γ -EC and glutathione pools in all lines but less glutathione was present in the leaves of the untransformed controls than the transformants under all growth conditions. Cadmium-induced changes in the activities of malic enzyme, isocitrate dehydrogenase and guaiacol peroxidase were less pronounced in the leaves of the transformed poplars overexpressing Γ -ECS than in the untransformed controls. Glutamate dehydrogenase and glutathione reductase activities were unchanged by exposure to cadmium. We conclude that overexpression of Γ -ECS activity and foliar glutathione accumulation in transformed poplar allows greater tissue cadmium accumulation but has only a marginal effect on cadmium tolerance in poplar.     

Poplar genome sequence: functional genomics in an ecologically dominant plant species

In addition to their value for wood products, members of the genus Populus (poplars) provide a range of ecological services, including carbon sequestration, bioremediation, nutrient cycling, biofiltration and diverse habitats. They are also widely used model organisms for tree molecular biology and biotechnology. The sequencing of the poplar genome to an approximately 6x depth adds to a long list of important attributes for research. These include facile transformation, vegetative propagation, rapid growth, modest genome size and extensive expressed sequence tags. Here, we discuss how the genome sequence and transformability of poplar, together with its high levels of genetic and ecological diversity, are enabling new insights into the genetic programs controlling ontogeny, ecological adaptation and environmental physiology of trees.     

Relationship between genotype and soil environment during colonization of poplar roots by mycorrhizal and endophytic fungi

Poplars are among the few tree genera that can develop both ectomycorrhizal (ECM) and arbuscular (AM) associations; however, variable ratios of ECM/AM in dual mycorrhizal colonizations were observed in the roots of a variety of poplar species and hybrids. The objective of our study was to analyze the effect of internal and external factors on growth and dual AM and ECM colonization of poplar roots in three 12–15-year-old common gardens in Poland. We also analyzed the abundance of nonmycorrhizal fungal endophytes in the poplar roots. The Populus clones comprised black poplars (Populus deltoides and P. deltoides × Populus nigra), balsam poplars (Populus maximowiczii × Populus trichocarpa), and a hybrid of black and balsam poplars (P. deltoides × P. trichocarpa). Of the three sites that we studied, one was located in the vicinity of a copper smelter, where soil was contaminated with copper and lead. Poplar root tip abundance, mycorrhizal colonization, and soil fungi biomass were lower at this heavily polluted site. The total mycorrhizal colonization and the ratio of ECM and AM colonization differed among the study sites and according to soil depth. The influence of Populus genotype was significantly pronounced only within the individual study sites. The contribution of nonmycorrhizal fungal endophytes differed among the poplar clones and was higher at the polluted site than at the sites free of pollution. Our results indicate that poplar fine root abundance and AM and ECM symbiosis are influenced by environmental conditions. Further studies of different site conditions are required to characterize the utility of poplars for purposes such as the phytoremediation of polluted sites.