植物反转录转座子的研究进展

反转录转座子是生物界中存在的一类可移动的遗传因子,其转座功能通过RNA介导反转录来实现.它在植物界中普遍存在,并在植物基因和基因组进化中扮演了一个极其重要的角色.概述了植物反转录转座子的类型结构及作为遗传工具在生物学中的作用.     

注意植物迁地保护中的遗传风险

稀有濒危植物迁地保护的长期目标之一就是要保护物种的遗传多样性和进化潜力。介绍了稀有濒危植物在植物园迁地保护过程中存在的一系列遗传风险。由于引种或取样的不足,容易导致被保存的物种缺乏足够的遗传代表性;盲目的引种、不合理的定植以及材料的来源不清则会导致稀有濒危植物的遗传混杂、近交衰退或杂交衰退;人为选择和生长环境的改变也容易造成濒危物种对迁地保护的遗传适应。在实际的迁地保护工作中,这些遗传风险往往被忽视。植物迁地保护中遗传风险将严重影响稀有濒危物种的回归和恢复。植物园应当重视濒危植物的遗传管理,以降低或避免迁地保护中的遗传风险。Abstract: Conserving genetic diversity of rare and endangered species and their evolutionary potential is one of the long-term goals of ex-situ conservation. Some potential genetic risks in ex-situ conservation in botanical gardens are presented. The preserved species may lack genetic representativity because of poor sampling. Inappropriate plantations, inadequate records and unclear kinships jeopardize endangered species to genetic confusion, inbreeding depression or outbreeding depression. Artificial selection and habitat conversion also potentially result endangered plants in adapting to ex-situ conservation, which had been usually overlooked. All the genetic risks can decrease the success of reintroduction and recovery. Therefore, appropriate genetic management should be carried out in botanical gardens to decrease or avoid genetic risks in ex-situ conservation.     

群体遗传结构中的基因流

群体遗传结构上的差异是遗传多样性的一种重要体现,对群体遗传结构的研究已有较久的历史,而其中的基因流研究近些年来越来越受到重视。它对群体遗传学、进化生物学、保护生物学、生态学有着极其重要的作用。虽然传统的群体遗传学能估测基因流大小,但它的精确性还有很大局限性。随着生物技术的进步,对基因流的研究逐渐向分子水平过渡,应用蛋白质电泳技术、分子标记技术(RAPD、RFLP、VNTR、ISSR、DNA测序等)方法对群体间基因流的流动水平进行了深入细致的研究。本文综述了群体遗传结构的几种模式：陆岛模式、海岛模式、阶石模式、距离隔离模式、层次模式,以及在群体遗传结构的几种模式基础上的基因流的研究方法、作用、地位和近些年来研究者的研究成果,并指出了这些方法的局限性。Abstract: The difference of population genetic structure is one of the important embodiments of genetic diversity. There is a long history of the study of population genetic structure, and the study of gene flow of population genetic structure is aroused more and more importance. It has an important effect on population genetics, evolution biology, conservation biology and ecology. Although the level of gene flow is estimated by traditional population genetics, there is a large restriction in its precision. With the development of biological technology, the methods of the research on gene flow reach the molecular level. Methods of protein electrophoresis and molecular markers (RAPD, RFLP, VNTR, ISSR and mitochondrial DNA) are used to research gene flow among populations. This paper introduces not only some models of population genetic structure: Continent-Island Model, Island Model, Stepping-Stone Model, Isolation-By-Distance Model and Hierarchical Model; but also the study methods, function and role of gene flow is based on models of population genetic structure, research achievements in recent years and the restriction of the methods.     

植物反转录转座子及其在功能基因组学中的应用

高等植物中的反转录转座子是构成植物基因组的重要成分之一.它分病毒家族和非病毒家族两类,病毒家族包括反转录病毒和类似于反转录病毒的非病毒转座子,病毒家族中的反转录转座子可再细分为Ty3-gypsy类和Ty1-copia类;非病毒家族可细分为LINE类和SINE类.正常情况下大部分反转录转座子不具有活性,某些生物或非生物因素胁迫可激活部分反转录转座子转座.反转录转座子自身编码反转录酶进行转录,以"拷贝-粘贴"的转座模式导致基因组扩增和进化.具有活性的反转录转座子通过插入产生新的突变,可作为一种基因标签技术,应用于功能基因组学研究,并成为研究植物基因功能和表达的重要技术平台.本文综述了近几年来在植物反转录转座子方面的研究进展,主要包括植物反转录转座子的结构、特征、活性及其对基因组的影响和它们在功能基因组学中的应用.     

MHC及其在种群遗传学和保护遗传学中的应用

主要组织相容性复合体（major histocompatibility complex,MHC）是脊椎动物体内与免疫应答调节密切相关的一个基因家族,是基因组中多态性最丰富的区域。通过MHC的遗传变异分析可以提供物种的遗传多样性水平、进化历史和种群动态,以及种群遗传结构等信息,并在濒危物种饲养繁殖种群的遗传管理中有重要应用。 MHC and Its Application in the Population and Conservation Genetics YANG Guang,CHEN Xu-yan,REN Wen-hua,YAN Jie Institute of Genetic Resources,Nanjing Normal University,Nanjing 210097,China Abstract:The major histocompatibility complex (MHC),with the highest genetic polymorphism,is a cluster of genes involved in immune response regulation in the vertebrates.MHC can provide information such as population genetic diversity,evolutionary history and population dynamics,and population genetic structure etc.It can also be applied in the captive breeding programme for endangered vertebrate species. Key words：major histocompatibility complex (MHC);genetic diversity,population viability;population genetic structure;captive breeding     

混合线性模型下猪群间遗传联系的度量

采用关联指数(IC)和决定系数(CD)两种方法,度量混合线性模型遗传评估下 猪群体间的遗传关联性。结果表明,加拿大安大略省的大约克夏猪、长白猪、杜洛克猪和汉普夏猪4个主要品种群体间具有良好的遗传联系。CD法既组合了数据结构和信息量,又考虑了预测误差方差和遗传变异性,是一个选择判断遗传评估精度的好方法。 Abstract:Two criteria for the measures of genetic connectedness in mixed linear model of genetic evaluation are used:the degree of connectedness(IC)and the generalized coefficient of determination(CD).The results indicated that the data of four dominant swine breeds:Yorkshire,Landrace,Duroc and Hampshire in Ontario,Canada are well connected.The CD,which combines data structure and amount of information and also accounts for both prediction error variance and genetic variability,is a good method to select for judging the precision of a genetic evaluation.     

表遗传学推动新一轮遗传学的发展

科学的发展孕育着突破,表遗传学研究推动着新一轮的遗传学的发展。表遗传学是研究没有DNA序列变化的、可遗传的表达改变。表遗传学不仅对医学和农业有重要的实践意义,而且还提供了理解遗传和进化的新观点。研究表明,人类基因组含有两类遗传信息,遗传学信息提供了合成生命所必需蛋白质的模板,而表遗传学信息提供了何时、何地和怎样地应用遗传学信息的指令;遗传学和表遗传学的关系有如“阴阳”,它们既相区别又协同参与调节生命活动。同时还讨论了基因的概念、进化和epigenetics的中文译名等问题。表遗传学研究应引起国内学术界的关注。Abstract: Scientific development is pregnant with a breakthrough, epigenetic studies are pushing the genetics forward. Epigenetics is the study of heritable changes in gene expression that occurs without a change in DNA sequence. Epigenetics not only has practical significance for medicine and agriculture, but also provides new views on understanding heredity and evolution. Human genome contains information in two forms: the genetic information provides the blueprint for the manufacture of all the proteins necessary to create a living thing while the epigenetic information provides instructions on how, where, and when the genetic information should be used. The interrelationship of genetics and epigenetics is like a yin-yan, they are different from each other, and cooperatively take part in regulation of a variety of living activities. In this paper concept of gene and problems of evolution has been also discussed according to epigenetic viewpoints.     

植物转座子与基因表达调控

植物转座子是植物基因组中可移动的DNA重复序列,在植物基因组进化、基因表达调控、系统发育和遗传多样性评价方面具有重要作用。综述了植物转座子分类、起源和转座机制以及转座子与宿主基因组间的表观遗传互作,阐述了不同转座子对基因表达调控方式,并对今后研究前景进行了展望,旨为全面了解植物转座子的功能提供参考。     

波尔山羊及其杂交改良后代群体遗传结构与亲缘关系研究

利用RAPD标记和POPGENE、PHYLIP及SPSS等统计分析软件,研究了波尔山羊及其杂交改良后代群体的遗传结构及遗传亲缘关系。结果表明,波尔山羊与其杂交改良后代间特别是高代杂种间具有相似的多态基因座百分率、等位基因数和基因多样性。随着级进杂交改良代数的递增,高代杂种之间以及与改良亲本之间的群体遗传结构的差异逐渐缩小,群体间的基因分化降低,基因流动和遗传相似度增加,遗传距离缩小,高代杂种与波尔山羊间具有更近的遗传亲缘关系。 Abstract:The genetic structure and relationship of Boer goat and its upgrading offspring to Tangshan Diary goat were studied using the RAPD marker and some statistical program,such as POPGENE,PHYLIP and SPSS.The results indicated that there were the similar percentage of polymorphic loci,observed and effective number of alleles,gene diversity between Boer goat and its upgrading offspring,especially higher upgrading offspring.With the increasing of upgrading,the difference of population structure decreased as well as the genetic distance and differentiation among higher upgrading offspring and their improving parental,but gene flow and genetic identity increased.There was a close genetic relationship between higher upgrading offspring and Boer goat.     

植物LTR反转录转座子的研究进展

反转录转座子是真核生物基因组中普遍存在的一类可移动的遗传因子,它们以RNA为媒介,在基因组中不断自我复制。在高等植物中,反转录转座子是基因组的重要成分之一。反转录转座子可以分为5大类型,其中以长末端重复（LTR）类型报道较多。LTR类型由于其首尾具有长末端重复序列,内部含有PBS、PPT、GAG和POL开放阅读框、TSD等结构,可以采用生物信息学软件进行预测。LTR反转录转座子的活性受到自身甲基化和环境因素的影响,DNA甲基化抑制反转录转座子转座,而外界环境的刺激能够激活转座子,从而影响插入位点周边基因的表达。同时由于LTR反转录转座子在植物中普遍存在,丰富的拷贝数以及多态性为新型分子标记（RBIP、SSAP、IRAP、REMAP）的开发提供了良好的素材。该文对近年来国内外有关植物反转录转座子的类型、结构特征、 LTR反转录转座子的活性及其影响因素、 LTR反转录转座子的预测以及标记开发等方面的研究进展进行综述。     

秋茄（Kandelia candel）的区域性种群（population）遗传结构

在台湾北部淡水河河口沼泽地带的秋茄（水笔仔）,依其林冠高度略可分成高、矮两个亚种群（Subpopulation）。矮生秋茄长在地面较高的河边,高生秋茄则沿着一条潮溪,长在较低处。使用淀粉凝胶方法研究同功酶组合型式,判断这个地区的区域种群的遗传结构,发现生长在沼泽区内较干燥地带的秋茄和长在潮湿地带的秋茄遗传上的分化程度很低（Fst= 0.043）。这可能是因为区内的基因流传很顺畅,抵消了可能发生的种群分化。     

基于遗传算法预测2D三向的蛋白质结构

本文基于范德华力势能预测2D三向的蛋白质结构。首先,将蛋白质结构预测这一生物问题转化为数学问题,并建立基于范德华力势能函数的数学模型。其次,使用遗传算法对数学模型进行求解,为了提高蛋白质结构预测效率,我们在标准遗传算法的基础上引入了调整算子这一概念,改进了遗传算法。最后,进行数值模拟实验。实验的结果表明范德华力势能函数模型是可行的,同时,和规范遗传算法相比,改进后的遗传算法能够较大幅度提高算法的搜索效率,并且遗传算法在蛋白质结构预测问题上有巨大潜力。     

Identification and population genetic comparison of three ascidian species based on mtDNA sequences

Ascidians are sessile marine chordate invertebrates found along seashores worldwide and are typically regarded as invasive organisms. Knowledge concerning their global genetic structure and subsequent invasive potential is limited. Here, we identified three ascidians—Ciona robusta, Ciona savignyi, and Styela clava from the northeast region of China using morphological characteristics and mitochondrial cytochrome c oxidase subunit I (cox1) as genetic marker. We additionally used phylogenetics to aid in the identification of these three species. The results of a population genetic analysis showed that among the three species, the level of haplotype diversity was particularly high within C. savignyi, and nucleotide diversity varied moderately. We divided the three species separately into native and invasive populations using 170 cox1 sequences from global resources to explore population genetic structure and invasive potential. Although in the network analysis Ciona spp. formed haplogroups of native and invasive populations, some haplotypes were still shared. We found that the haplotypes did not cluster within the network of S. clava. Our AMOVA results also showed that Ciona spp. had a weak genetic structure, and less genetic differentiation was present in S. clava. These data suggest that there are extensive incursions of these three ascidians into different geographical regions. Global comparisons of ascidian populations will help in the understanding of their population genetic structure and invasive potential, hence providing important insights regarding conservation as well as management.     

松嫩平原中部地区羊草种群的遗传结构研究

松嫩平原中部地区的羊草,依其生长的微环境不同可分成灰绿色和黄绿色两种叶色类型的种群。移栽实验表明,这两类种群实际上是灰色和灰绿色两种类型的混生群体。采用淀粉凝胶电泳技术及等位酶分析方法测定了不同生境、不同分类种群的遗传结构,发现羊草种群遗传变异度很高;但是无论如何归属,这一草原区域上的羊草种群遗传分化程度很低(FST ≤ 0.034)。这可能与羊草为异花授粉、不同类型混生及种群间基因流强度大有关。     

High gene flow in the American badger overrides habitat preferences and limits broadscale genetic structure

Habitat associations are a function of habitat preferences and dispersal capabilities, both of which can influence how species responded to Quaternary climatic changes and contemporary habitat heterogeneity. Predicting resultant genetic structure is not always straightforward, especially in species where high dispersal potential and habitat preferences yield opposing predictions. The American badger has high dispersal capabilities that predict widespread panmixia, but avoids closed‐canopy forests and clay soils, which could restrict gene flow and create ecologically based population genetic structure. We used mitochondrial sequence and microsatellite data sets to characterize how these opposing forces contribute to genetic structure in badgers at a continent‐wide scale. Our data revealed an overall lack of ecologically based population genetic structure, suggesting that high dispersal capabilities were sufficiently realized to overcome most habitat‐based genetic structure. At a broadscale, badger gene flow is limited only by geographic distance (isolation by distance) and large water barriers (Lake Michigan and the Mississippi River). The absence of genetic structure in a species with strong avoidance of unsuitable habitats advances our understanding of when and how genetic structure emerges in widespread, highly mobile species.     

Unexpectedly complex gradation of coral population structure in the Nansei Islands,Japan

To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence‐based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.     

Population genetic analyses of Hypoplectrus coral reef fishes provide evidence that local processes are operating during the early stages of marine adaptive radiations

Large-scale, spatially explicit models of adaptive radiation suggest that the spatial genetic structure within a species sampled early in the evolutionary history of an adaptive radiation might be higher than the genetic differentiation between different species formed during the same radiation over all locations. Here we test this hypothesis with a spatial population genetic analysis of Hypoplectrus coral reef fishes (Serranidae), one of the few potential cases of a recent adaptive radiation documented in the marine realm. Microsatellite analyses of Hypoplectrus puella (barred hamlet) and Hypoplectrus nigricans (black hamlet) from Belize, Panama and Barbados validate the population genetic predictions at the regional scale for H. nigricans despite the potential for high levels of gene flow between populations resulting from the 3-week planktonic larval phase of Hypoplectrus . The results are different for H. puella , which is characterized by significantly lower levels of spatial genetic structure than H. nigricans . An extensive field survey of Hypoplectrus population densities complemented by individual-based simulations shows that the higher abundance and more continuous distribution of H. puella could account for the reduced spatial genetic structure within this species. The genetic and demographic data are also consistent with the hypothesis that H. puella might represent the ancestral form of the Hypoplectrus radiation, and that H. nigricans might have evolved repeatedly from H. puella through ecological speciation. Altogether, spatial genetic analysis within and between Hypoplectrus species indicate that local processes can operate at a regional scale within recent marine adaptive radiations.     

Genetic drift and anthropometric variation in Ireland

The effect of genetic drift on the genetic structure of seven Irish populations was investigated using anthropometric data collected during the 1890s on 259 adult males. These populations ranged in size from 769 to 3757, were relatively stable over time, and were located within 119 km of one another. Two populations are known to have experienced considerable English admixture. Data on ten anthropometric variables (three body measures and seven craniofacial measures) were adjusted for age and used to compute a relationship (R) matrix. The R matrix was converted into a distance measure and compared with a potential genetic drift distance measure, defined as (1/Ni + 1/Nj), where Ni and Nj are the effective population sizes of groups i and j (derivation of this formula is presented). Distances were rank-transformed, and the correlation between their pairwise elements was computed using matrix permutation methods to assess significance. Under the hypothesis that drift affects anthropometric variation, these correlations are expected to be positive. The correlation between anthropometric distance and potential genetic drift distance is 0.123, which is not significantly different from 0 (P = 0.368). When a multiple regression model is used to adjust for geographic distance and English admixture, the partial correlation (0.369) is significant (p = 0.021). As part of further analysis of the genetic structure of these populations, the same analyses were repeated using a distance matrix derived from surname frequencies. The correlation of surname distance and potential genetic drift distance is 0.164, which is not significant (p = 0.264). When the multiple regression model is applied, the correlation is 0.401, which is borderline significant (p = 0.055). These results show the influence of genetic drift, local migration, and admixture on Irish population structure.     

Hydrography and population genetic structure in brook charr (Salvelinus fontinalis, Mitchill) from eastern Canada

Despite the abundance of studies of genetic diversity in freshwater fishes, few have specifically addressed the role of habitat structure in partitioning genetic variance within and among populations. In this study, we analysed the variability of six microsatellite loci among 24 brook charr population samples in order to correlate hydrographic structure with genetic organization. These populations originated from three Canadian National parks (Kouchibouguac, Fundy and Forillon) that showed distinct hydrographic structure. Considering the general characteristics of these habitats, we formulated specific hypotheses in regard to genetic structure, which were principally based on the potential for gene flow and population size associated with each habitat. The hierarchical analysis of molecular variance and the genetic distances computed among populations revealed that habitat structure analyses constitute an important, but insufficient, predictor of genetic structure. We discuss the importance of habitat complexity on genetic structure in the context of management and conservation.     

Phylogeography of a migratory songbird across its Canadian breeding range: Implications for conservation units

The objectives of this study were to describe and evaluate potential drivers of genetic structure in Canadian breeding populations of the Ovenbird, Seiurus aurocapilla. We performed genetic analyses on feather samples of individuals from six study sites using nuclear microsatellites. We also assessed species identity and population genetic structure of quill mites (Acariformes, Syringophilidae). For male Ovenbirds breeding in three study sites, we collected light‐level geolocator data to document migratory paths and identify the wintering grounds. We also generated paleohindcast projections from bioclimatic models of Ovenbird distribution to identify potential refugia during the last glacial maximum (LGM, 21,000 years before present) as a factor explaining population genetic structure. Birds breeding in the Cypress Hills (Alberta/Saskatchewan) may be considered a distinct genetic unit, but there was no evidence for genetic differentiation among any other populations. We found relatively strong migratory connectivity in both western and eastern populations, but some evidence of mixing among populations on the wintering grounds. There was also little genetic variation among syringophilid mites from the different Ovenbird populations. These results are consistent with paleohindcast distribution predictions derived from two different global climate models indicating a continuous single LGM refugium, with the possibility of two refugia. Our results suggest that Ovenbird populations breeding in boreal and hemiboreal regions are panmictic, whereas the population breeding in Cypress Hills should be considered a distinct management unit.