青鳉Tol2转座子研究进展

鳉鱼Tol2转座子作为hAT（hobo/Activayor/Tam3）转座子家族中的一员,是目前所发现的唯一的天然存在且有转座活性的脊椎动物转座子。本文从Tol2转座子的结构,转座机制和应用方面作一个综述。     

植物转座子

在简要介绍转座子的种类、结构和特性的基础上,综述了利用转座子诱变、基因标签和克隆方面的研究进展。     

利用Tol2转座子构建转基因草金鱼初探

青鳉Tol2转座子是脊椎动物中发现的第一例天然具有活性的转座子,目前已经被成功应用于多种模式动物的转基因研究中。采用PCR的方法以质粒pCAgcGH为模板亚克隆出一段含有草鱼生长激素(GH)5个外显子、鲤鱼β-actin启动子及多个酶切位点的序列,并将这段序列与经双酶切处理的质粒pTol2-MCS-EGFP进行重组连接,得到重组质粒pTol2-GH-EGFP。采用显微注射的方法将重组质粒pTol2-GH-EGFP与体外合成的Tol2转座酶mRNA一起注入草金鱼受精卵中。通过观察绿色荧光和PCR检验绿色荧光蛋白和GH基因的表达,筛选出成功转入外源基因的草金鱼。阳性表达检出率为17.3%。利用Tol2转座子构建转基因草金鱼,不仅丰富了Tol2转座子的应用范围,而且为进一步利用Tol2转座元件进行观赏鱼转基因及基因表达研究奠定了基础。     

水稻转座子研究进展

转座子是植物基因组的重要组成部分,对于研究植物基因组进化等具有重要意义。随着水稻全基因组测序计划的开展和完成,水稻转座子研究取得了极大进展,目前已经在水稻基因组中发现了几乎所有类型的转座子,约占水稻基因组的35%。在正常情况下,大多数水稻转座子不具有转座活性,但是在特定的条件下（如组织培养或辐射等）,水稻基因组中沉默的转座子可以被激活,从而可能导致插入突变并影响基因的表达。在水稻中已鉴定出6个有活性的转座子,其中Tos17已被应用到水稻功能基因组研究中。转座子序列的新的分子标记转座子展示（transposon display,TD）现已被开发,并在水稻遗传作图和遗传分化研究中得到应用。     

水稻转座子研究进展

转座子是植物基因组的重要组成部分, 对于研究植物基因组进化等具有重要意义。随着水稻全基因组测序计划的开展和完成, 水稻转座子研究取得了极大进展, 目前已经在水稻基因组中发现了几乎所有类型的转座子, 约占水稻基因组的35%。在正常情况下, 大多数水稻转座子不具有转座活性, 但是在特定的条件下(如组织培养或辐射等), 水稻基因组中沉默的转座子可以被激活, 从而可能导致插入突变并影响基因的表达。在水稻中已鉴定出6个有活性的转座子, 其中Tos17已被应用到水稻功能基因组研究中。转座子序列的新的分子标记转座子展示(transposon display, TD)现已被开发, 并在水稻遗传作图和遗传分化研究中得到应用     

Tol2转座子系统在转基因动物中的应用

Tol2是在青鳉鱼基因组中发现的一种具有自主性的转座子元件.它编码转座酶,催化Tol2转座子结构中5’端200 bp和3’端150 bp序列发生转座反应.Tol2的多种特性,如可携带大片段外源DNA、单拷贝整合效率高、转座子活性强等,使得以Tol2特座子系统为载体的转基因技术在多种生物中得到应用.综述了Tol2转座子系统的结构、特性以及近年来在多种动物转基因中的应用.     

玉米转座子,GBSSI基因及表达研究进展

与淀粉结合的淀粉合成酶 (ＧＢＳＳＩ)基因又叫做腊质基因 (Ｗｘ) ,是在小麦、水稻、玉米、马铃薯、木薯等植物中决定直链淀粉合成的基因。玉米中ＧＢＳＳＩ基因因其突变形成等位基因是由转座子诱发形成的 ,对转座子及ＧＢＳＳＩ基因特征化的研究 ,将对玉米近二十年来停止不前的单产提高问题及淀粉品质改良起着至关重要的作用。1　转座子与ＧＢＳＳＩ基因早在 1 943年Ｓｐｒａｇｕｅ[1] 等识别了玉米Ｗｘ基因位点 ,并证明了其决定胚乳和花粉中直链淀粉的合成。Ｎｅｉｓｏｎ和Ｒｉｎｅｓ[2 ] 及Ｔｓａｉ[3] 分别在 1 96 2年和 1 974年分别证…     

Tc1/Mariner转座子超家族的研究进展

随着高通量测序技术的迅猛发展,越来越多的生物基因组注释结果表明：转座子几乎存在于所有生物的基因组中,是大多数生物基因组的重要组分。其中,Tc1/Mariner转座子是自然界中分布最广泛的一类DNA转座子超家族,在自然界已经发现14个有活性的Tc1/Mariner转座子(如Minos,Mos1等),另外通过分子重构也获得高活性的人工转座子,如睡美人转座子(Sleeping Beauty, SB)。SB和Mos1等转座子作为基因转移载体已被广泛应用于转基因、基因捕获和基因治疗等领域的研究中,并取得了很好的应用效果。本文将重点综述Tc1/Mariner转座子的结构、分类、分布、转座机制、活性转座子的挖掘,及其在转基因、基因捕获和基因治疗等研究领域的应用。     

类Tc1转座子研究进展

转座子广泛存在于各种生物基因组中,能在染色体不同位点间转座,并在基因组中大量扩增.转座子的活动能引起生物基因组或基因的重组和变异,加速生物多样性及其进化速率,被视为生物基因组进化的内在驱动.转座子分2类：反转座子和DNA转座子.类Tc1转座子是DNA转座子超级家族中种类最多、分布最广的一类.本文简要概述了类Tc1转座子的结构特征,及其扩增、转座和迸发的机制,并展望了其应用和研究方向.     

Albinism Due to Transposable Element Insertion in Fish

The i locus of the medaka fish, Oryzias latipes, is responsible for tyrosinase expression, and several mutant alleles have been identified. The genotype i¹/i¹ exhibits a complete albino phenotype, having pale orange-red skin and red eyes. This mutant lacks in vivo tyrosinase activity. The genotype i⁴/i⁴, on the other hand, shows a quasi-albino phenotype with skin as bright as that of i¹/i¹ but with red-wine-colored eyes. At the light microscope level, reduced pigmentation is observed both in the skin and eyes of this mutant. The tyrosinase genes for the i¹ and the i⁴ alleles were cloned and sequenced, and compared with that of the wild-type tyrosinase gene. The i¹ allele was found to contain a 1.9-kb transposable element in the 1st exon, and the i⁴ allele was found to contain a 4.7-kb transposable element in the 5th exon. Both i¹ and i⁴ are alleles that were found in a commercial breeding population. The insertion of a transposable element thus appears to constitute a natural cause of mutations that cause albinism in this organism.     

苏云金芽孢杆菌转座因子研究进展

近年来的研究发现苏云金芽孢杆菌转座因子和许多毒力因子可能是紧密联系的。由于转座因子的特殊性质,使它们在现代农业生物技术中有着广泛的应用前景,科学家对苏云金芽孢杆菌转座因子的研究也在不断深入。本文主要针对苏云金芽孢杆菌转座因子的研究进展进行综述,并对发展前景进行展望。     

Transposable element-induced mutations of the viviparous-1 gene in maize

The viviparous-1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator-induced mutant allele, vp1-mum-1, by transposable element tagging has allowed analysis of several transposon-induced vp1 mutants. In the vp1-Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C-terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator- derived allele, vp1-mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild-type vp1 expression to a mutant condition. The vp1-mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild-type germinal revertants derived from vp1-mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1-mum2 states that exhibit wild-type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1-mum2 somatic mutation.     

Gene Transfer and Cloning of Flanking Chromosomal Regions Using the Medaka Fish Tol2 Transposable Element

For the ultimate purpose of developing genetic tools using the medaka fish Tol2 transposable element, we examined whether it can transfer a marker gene into the fish genome and also be applied for cloning of chromosomal regions adjacent to insertion points. An internal region of Tol2 was removed and replaced with the green fluorescent protein (GFP) gene and a bacterial plasmid replication origin. This modified Tol2 clone was microinjected into fertilized eggs together with messenger RNA for the Tol2 transposase. The GFP gene was found to be integrated into chromosomes and transmitted to subsequent generations. Restriction enzyme digestion of genomic DNA of a transformant fish, followed by ligation and introduction into bacteria, produced a plasmid containing the entire element and flanking chromosomal regions. Sequencing analysis of this clone demonstrated transposition of the element in the germline of the first generation. Thus, the basic requirements for a gene transfer vector and gene tagging system were fulfilled. Received July 30, 2001; accepted October 4, 2001     

Transient and permanent gene transfer into the brain of the teleost fish medaka (Oryzias latipes) using human adenovirus and the Cre-loxP system

In this study, we demonstrated that human type-5 adenovirus infected the brain of the teleost fish, medaka (Oryzias latipes), in vivo. Injection of adenoviral vector into the mesencephalic ventricle of medaka larvae induced the expression of reporter genes in some parts of the telencephalon, the periventricular area of the mesencephalon and diencephalon, and the cerebellum. Additionally, the Cre-loxP system works in medaka brains using transgenic medaka carrying a vector containing DsRed2, flanked by loxP sites under control of the β-actin promoter and downstream promoterless enhanced green fluorescent protein (EGFP). We demonstrated that the presence of green fluorescence depended on injection of adenoviral vector expressing the Cre gene and confirmed that EGFP mRNA was transcribed in the virus-injected larvae.     

植物脂肪酸代谢途径遗传调控的研究进展

目前,利用传统育种方法改良油料作物脂肪酸组分已取得巨大成功,通过有性杂交、X-射线或EMS处理等方法都可用来修饰存在于油菜中脂肪酸的性质。国外已培育出高棕榈酸、高或低亚油酸、高油酸和无芥酸的油菜品种。但由于油料作物基因池(Gene Pool)的局限性使得育种学家不得不寻找其他种质资源。随着基因克隆和遗传转化技术的进步,通过基因工程改良油料作物品质已成可能。本文主要介绍了植物脂肪酸的代谢途径以及通过操纵TAG的生物合成来改变油的成分等研究,其中主要包括脂肪酸链长度的改良、饱和度改良、增加脂肪酸含量以及新的不饱和脂肪酸的改良等方面。不久的将来,转基因油料作物中将会产生更有价值的脂肪酸造福于人类。     

Inference of Transposable Element Ancestry

Most common methods for inferring transposable element (TE) evolutionary relationships are based on dividing TEs into subfamilies using shared diagnostic nucleotides. Although originally justified based on the “master gene” model of TE evolution, computational and experimental work indicates that many of the subfamilies generated by these methods contain multiple source elements. This implies that subfamily-based methods give an incomplete picture of TE relationships. Studies on selection, functional exaptation, and predictions of horizontal transfer may all be affected. Here, we develop a Bayesian method for inferring TE ancestry that gives the probability that each sequence was replicative, its frequency of replication, and the probability that each extant TE sequence came from each possible ancestral sequence. Applying our method to 986 members of the newly-discovered LAVA family of TEs, we show that there were far more source elements in the history of LAVA expansion than subfamilies identified using the CoSeg subfamily-classification program. We also identify multiple replicative elements in the AluSc subfamily in humans. Our results strongly indicate that a reassessment of subfamily structures is necessary to obtain accurate estimates of mutation processes, phylogenetic relationships and historical times of activity.