植物抗污染进化及其遗传生态学代价

植物抗污染进化及其遗传生态学代价熊治廷（武汉大学环境科学系,４３００７２）ＰｏｌｕｔｉｏｎＲｅｓｉｓｔａｎｔＥｖｏｌｕｔｉｏｎｉｎＰｌａｎｔｓａｎｄＩｔｓＧｅｎｅｃｏｌｏｇｉｃａｌＣｏｓｔｓ．ＸｉｏｎｇＺｈｉｔｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＥｎｖ...     

序列消除与异源多倍体植物基因组的进化

经杂交后多倍化形成的异源多倍体植物,被认为在其形成的早期阶段经历了DNA序列消除过程。发生消除的序列既涉及到高拷贝的序列也有低拷贝的序列,而且大多数情况下倾向于消除来自其中一个亲本的序列。序列消除的模式因基因组组成和物种的不同而有差异,并且可能受到细胞质的影响。尽管序列消除的分子机制还不是很清楚,但很多证据已表明非同源染色体之间的互作不是主要的原因。目前认为,序列消除增加了非同源染色体之间的差异,为多倍化后在减数分裂过程中快速恢复二倍化的染色体配对模式提供了物质基础,这样更有利于多倍体在自然界快速稳定。     

植物人工异源多倍体的遗传及后遗传变化

据估计,70%以上的显花植物在其生活史上至少发生过一次以上的多倍化。传统的有关多倍性的观点认为,多倍体基因组应是其双亲基因组的积加。但是,有些合成异源多倍体的基因组发生了广泛的遗传及后遗传变化。这些变化包括亲本DNA序列丢失、核仁显性、DNA甲基化模式改变、基因沉默、反转座子激活等。亲本序列丢失可能与部分同源序列间重组有关,而亲本基因沉默可能与同源性依赖的基因沉默及RNA干涉等有关。     

异源多倍体植物核rDNA序列的同步进化

同步进化是异源多倍体植物核rDNA序列进化的重要方式,同步进化的程度在不同植物类群中存在较大差异,有些类群中同步进化力量较强,核rDNA重复序列间已经纯合或接近纯合,有些类群中同步进化的力量较弱,可观察到序列的杂合性。同步进化的机制主要是不等交换和基因转换,并受异源多倍体形成年代、生殖方式、基因突变率等因素的影响。     

小麦染色体组的起源与进化

小麦是世界上最重要也是最古老的作物之一,同时它还是典型的多倍体植物,关于它的起源与进化至今还是１个未彻底揭开的谜。长期以来各国学者在这方面进行了大量研究。１小麦属的分类小麦属禾本科（Ｃｒａｍｉｎｅａｅ）、小麦族（Ｔｒｉｔ－ｉｃｅａｅ）、小麦亚族（Ｔｒ...     

禾木科植物染色体消除型远缘杂交的研究进展

植物远缘杂交是作物育种中广泛应用的技术。除了核型稳定的种间杂交可以获得杂种以外,还可以利用核型不稳定的种间杂交后父本染色体消除的现象,通过胚培养和染色体加倍处理获得加倍单倍体(DH)植株。然而从小麦×玉米杂交获得的DH后代与其理论上应完全同质的遗传表现却不相符,总有2～5％的DH植株发生了形态学变异。最近的研究证明。通过小麦×玉米的受精作用,一些玉米特异DNA可以被转移到小麦DH后代的基因组中。     

远缘杂交和异源多倍体化技术在水稻育种中的应用

从野生稻遗传资源在育种中的作用出发,概述了栽培稻与野生稻远缘杂交和多倍体化在水稻育种中的应用。对远缘杂交中的杂交不亲和性以及杂种不育等问题采用激素处理、胚挽救等途径解决,对所获杂种从形态学、细胞学、生物化学以及分子生物学等多方面鉴定,对栽野杂种存在的野生性状通过选择与改造相结合的方法而淘汰,对其有利基因则加以选择和聚合以获得稳定优良品种。这些从理论上和实践上证明远缘杂交和多倍体化相结合的异源多倍体化是获得高产优质水稻新品种的一条新途径。     

染色体数据的挖掘及其在植物多样性进化研究中的利用

多倍化(或全基因组加倍)是植物物种形成的重要途径,现存的被子植物可能都发生过一次甚至多次多倍化事件。多倍化传统的定义是染色体数目相对于祖先类群呈整倍性增加。其中最常用的研究方法是核型分析,核型能够提供物种的基本细胞学参数,包括染色体数目、倍性水平、核型不对称性、核型变异系数等。目前核型研究的趋势表现出从物种基本核型参数分析逐渐演化到多类群、多学科交叉融合的特点:一方面植物核型分析从种群、物种、科属的类群到生命之树,探讨染色体核型在各支系的进化特征、趋势以及驱动植物系统进化的细胞学机制;另一方面探讨和分析区域或生态系统植物区系的染色体谱或倍性等细胞学特征,可以探究区域地质环境变化或生态环境对染色体倍性等的影响,或通过区域染色体谱的构建,分析区域植物区系的形成和进化历史。因而,植物核型研究为系统发育、分子系统进化、生命之树以及植物区系地理的起源和演化研究提供了新思路。越来越多的新方法、新手段在植物核型分析与多倍化研究中得到运用,从而揭示了植物类群或植物区系的染色体进化以及细胞地理特征。今后植物细胞学研究趋势会向多学科交叉融合,整合各研究领域证据,从不同水平角度综合分析植物核型多样性形成的原因及意义,从而更加全面地认识和理解植物物种多样化与物种形成原因。     

植物异源多倍体进化中基因表达的变化

多倍化是植物物种进化的主要动力, 异源多倍体植物在形成早期发生着快速的基因表达变化。本文概述了异源多倍体植物中基因表达变化的特点, 包括基因的沉默、激活和部分同源基因表达水平的变化, 探讨了基因表达变化的分子机制和生物学意义, 并对研究中的问题进行了分析和展望。     

从CIMMYT引进的人工合成六倍体小麦D染色体组微卫星分子标记的遗传差异

采用微卫星（SSR）分子标记技术,选用23个D染色体组特异性引的对来自CIMMYT的26份人工合成六倍体小麦D染色体组的遗传多样性进行了分析。研究发现,26份材料在D染色体组上存在丰富的等位基因变异（92个）,平均每个基因座为4个。遗传距离计算结果也显示,26份材料D染色体组之间具有较大的遗传差异,平均遗传距离高达0．4955。因此,人工合成六倍体小麦D染色体组中存在丰富的遗传多样性,可以作为拓宽普通小麦遗传基础的新的遗传变异来源。研究还发现,由同一个粗山羊草基因型与不同硬粒小麦杂交合成的人工合成六倍体小麦（如合成种17和18）在所用检测的23个基因座中有3个存在差异,说明小麦在多倍化后,供体基因组在重复序列区域会发生遗传分化。     

Major transitions in evolution by genome fusions: from prokaryotes to eukaryotes,metazoans, bilaterians and vertebrates

Journal of Structural and Functional Genomics - The major transitions in human evolution from prokaryotes toeukaryotes, from protozoans to metazoans, from the first animals tobilaterians and...     

Generality and characteristics of genetic and epigenetic changes in newly synthesized allotetraploid wheat lines

Previous studies have shown rapid and extensive genomic instability associated with early stages of allopolyploidization in wheat.However, these studies are based on either a few pre-selected genomic loci or genome-wide analysis of a single plant individual for a given cross combination, thus making the extent and generality of the changes uncertain.To further study the generality and characteristics of allopolyploidization-induced genomic instability in wheat, we investigated genetic and epigenetic changes from a genome-wide perspective (by using the AFLP and MSAP markers) in four sets of newly synthesized allotetraploid wheat lines with various genome constitutions, each containing three randomly chosen individual plants at the same generation.We document that although general chromosomal stability was characteristic of all four sets of allotetraploid wheat lines, genetic and epigenetic changes at the molecular level occurred in all these plants, with both kinds of changes classifiable into two distinct categories, i.e., stochastic and directed.The abundant type of genetic change is loss of parental bands while the prevalent cytosine methylation pattern alteration is hypermethylation at the CHG sites.Our results have extended previous studies regarding allopolyploidization-induced genomic dynamics in wheat by demonstrating the generality of both genetic and epigenetic changes associated with multiple nascent allotetraploid wheat lines, and providing novel insights into the characteristics of the two kinds of induced genomic instabilities.     

Genome evolution in polyploids

Polyploidy is a prominent process in plants and has been significant in the evolutionary history of vertebrates and other eukaryotes. In plants, interdisciplinary approaches combining phylogenetic and molecular genetic perspectives have enhanced our awareness of the myriad genetic interactions made possible by polyploidy. Here, processes and mechanisms of gene and genome evolution in polyploids are reviewed. Genes duplicated by polyploidy may retain their original or similar function, undergo diversification in protein function or regulation, or one copy may become silenced through mutational or epigenetic means. Duplicated genes also may interact through inter-locus recombination, gene conversion, or concerted evolution. Recent experiments have illuminated important processes in polyploids that operate above the organizational level of duplicated genes. These include inter-genomic chromosomal exchanges, saltational, non-Mendelian genomic evolution in nascent polyploids, inter-genomic invasion, and cytonuclear stabilization. Notwithstanding many recent insights, much remains to be learned about many aspects of polyploid evolution, including: the role of transposable elements in structural and regulatory gene evolution; processes and significance of epigenetic silencing; underlying controls of chromosome pairing; mechanisms and functional significance of rapid genome changes; cytonuclear accommodation; and coordination of regulatory factors contributed by two, sometimes divergent progenitor genomes. Continued application of molecular genetic approaches to questions of polyploid genome evolution holds promise for producing lasting insight into processes by which novel genotypes are generated and ultimately into how polyploidy facilitates evolution and adaptation.     

Spartina anglica C. E. Hubbard: a natural model system for analysing early evolutionary changes that affect allopolyploid genomes

Spartina anglica arose during the end of the 19th century in England by hybridization between the indigenous Spartina maritima and the introduced East American Spartina alterniflora and following genome duplication of the hybrid ( S.  ×  townsendii ). This system allows investigations of the early evolutionary changes that accompany stabilization of a new allopolyploid species in natural populations. Various molecular data indicate that S. anglica has resulted from a unique parental genotype. This young species contains two distinctly divergent homoeologous genomes that have not undergone extensive change since their reunion. No burst of retroelements has been encountered in the F₁ hybrid or in the allopolyploid, suggesting a 'structural genomic stasis' rather than 'rapid genomic changes'. However, modifications of the methylation patterns in the genomes of S.  ×  townsendii and S. anglica indicate that in this system, epigenetic changes have followed both hybridization and polyploidization.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 475–484.     

Cloning of a polymorphic canine genetic marker which maps to human chromosome 9

We describe the cloning of a novel canine polymorphic genetic marker which maps to human chromosome 9. The sequence is 2092 bp, 59% GC rich, and contains three GC boxes. Chemilumin-escent probing of zooblots showed evolutionary conservation. Dogs have three Bam HI alleles: 2.3 kb, 2.1 kb and 1.7 kb. Allele frequencies in 17 unrelated dogs representing 13 breeds are presented. Polymorphism for the 1.7-kb allele in beagles is common. The 2.1-kb allele is probably the ancestral allele since it is the most common and is also noted in the Cape hunting dog. Interestingly, in more than 50 dogs tested to date, the 2.3-kb allele has been found only in miniature and giant schnauzers. This points to a common origin for these two breeds.     

Comparative isozyme polymorphisms of north American eastern gamagrass,Tripsacum dactyloides var.dactyloides and maize,Zea mays L.

Random samples, consisting of at least 100 individual seedlings, were taken from the diploid (2n=2x=36) eastern gamagrass (Tripsacum dactyloides var.dactyloides) and assayed to determine which of 12 enzyme marker loci and isozyme systems would be most informative in providing satisfactory resolution of both maize andTripsacum isozyme systems. For comparison, eight maize inbreds were included in the study to aid evaluation and comparison of the various isozyme systems. In addition, evaluations were conducted to identify if the identified optimum isozyme system could be used to detectTripsacum introgression in maize following a maize ×Tripsacum backcrossing scheme. Using the established isozyme techniques for maize (Zea mays L.), theAdh, Pgd, Cat, Est, B-Glu, Got, Idh, Tpi isozyme systems detected no polymorphism among theTripsacum individuals assayed. TheEst andB-Glu systems forTripsacum were unscorable due to poor staining and resolution. TheAcp, Mdh, Pgm, andPhi isozyme systems were found to be satisfactory markers for differentiating between eastern gamagrass individuals as well as detectingTripsacum introgression in maize. The availability of useful isozyme systems which can simultaneously provide significant isozyme resolution of maize,Tripsacum and maize-Tripsacum backcross hybrids, on a single gel system, will be useful for the detection of marker assistedTripsacum introgression into maize. In addition, the identification of a set of variable biochemical markers should also assist breeding, selection and genetic manipulations in eastern gamagrass.The use of company names in this publication does not imply endorsement by the USDA-ARS, or the product names of criticism of similar ones not mentioned. All programs and services of the U.S. Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.