人工诱发油莱孤雌单倍体的研究

我们在甘兰型油菜育种工作中试用了人工诱发孤雌生殖的方法。试验结果表明,油菜种间远缘授粉可以诱发孤雌单倍体,油菜的孤雌单倍体一般形似母本,但体形较小,叶片和花朵也较小,雄芯能育性低,早期花朵多数败育,叶片表皮的气孔较小,气孔保卫细胞里的叶绿粒较少,体细胞的染色体数为19。为了早期鉴定出油菜孤雌单倍体,我们使用了子叶叶形、幼叶刺毛、幼苗色泽等性状作为早期标记性状。对于早期鑑定出来的油菜孤雌单倍体,我们通过早期培育和人工辅助自交等方法,促使其二倍化、提高其结实性,获得了若干纯合自交系种子。在计数染色体数目方面,我们使用了适于在油菜田间取材的简易制片方法。人工诱发孤雌单倍体的育种方法,比较适合在农村开展群众性的育种试验。     

烟草组织培养中染色体不稳定性的研究

单倍体烟草(n=24)叶片在离体培养条件下,染色体数目和结构发生明显变化.离体培养早期(3—5天).叶外植体细胞中的染色体数倍性已有明显变化,除单倍体外尚有二倍体、三倍体、四倍体及其各种类型的非整倍体,观察细胞中的染色体数变动在8—96之间.随着培养时间的延长,烟草叶外植体细胞在分裂、增殖、分化、发育成再生植株的过程中,亚单倍体和单倍体细胞比率逐渐上升,而最终占据绝对优势.在离体培养中除了染色体数目变异之外,还经常看到染色体断片、后期桥、落后染色体和微核等染色体结构改变.     

孤雌生殖来源杂交油菜3529X奥罗杂种优势与核酸含量的关系

本实验研究表明,孤雌生殖单倍体杂交油菜3529×奥罗的杂种优势,与其DNA,RNA含量的增加有关     

两种寄生吸虫的染色体组型和繁殖方式

以精巢细胞染色体空气干燥标本制备技术,研究两种寄生吸虫的有丝分裂和减数分裂染色体,结果表明:片形吸虫体细胞染色体,2n=20,包括三对中着丝点、一对亚中着丝点、五对亚端着丝点、一对端着丝点染色体,这和前人报道的片形吸虫染色体形态有些差异。另外,群体中有65.3％的虫体细胞染色体为三倍体,3n=30。观察片形吸虫的配子形成,发现二倍体个体细胞减数分裂能正常进行,形成单倍体配子;三倍体个体细胞不进行减数分裂,也没有配子形成,推测二倍体虫体的生殖方式为有性繁殖,而三倍体虫体的生殖方式为孤雌生殖。并认为我国存在的两种片形吸虫:大片吸虫和肝片吸虫,有三倍体和二倍体两种,分别行无性繁殖和有性繁殖。     

单倍体育种——林木快速育种的新方法

一、林木单倍体育种的意义植物花粉(雄配子体)通过传粉作用与卵细胞(雌配子体)相结合形成受精卵。受精卵发育成为种子。种子以及由种子长成的植株的细胞中,包含着来自精、卵即父母双方的两套遗传物质——染色体,这从细胞遗传学上说是二倍体。花粉和卵细胞分别由花粉母细胞和大孢子母细胞经减数分裂而形成。它们的染色体数目为体细胞染色体的一半,也就是说,在花粉和卵细胞中只有一套染色体,因而是单倍体。花     

甘蓝型油菜与蓝花子属间倍半二倍体的形成及其细胞遗传学特性

对甘蓝型油菜与蓝花子的属间远缘杂交得到的杂种Ｆ＿１，经加倍后获得双二倍体植株。该植株作母本再与甘蓝型油菜杂交获得其倍半二倍体．用充气液体培养基加８－羟基喹啉预处理，对不能以根尖为材料作染色体制片的植物，以其幼嫩花蕾进行体细胞染色体制片，对甘蓝型油菜与蓝花子属间倍半二倍体的细胞遗传学特性进行了研究，该植物的染色体数目为２ｎ＝４７．大多数ＰＭＣｓ的染色体在减数分裂过程中配对不规则，并在后期Ⅱ中出现多极分裂现象．     

甘蓝型油菜与蓝花子属间倍半二倍体的形成及其细胞遗传…

对甘蓝型油菜与蓝花子的属间远缘杂交得到的杂种Ｆ１，经加倍后获得双二倍体植株，该植株作母本再与甘蓝型油菜杂交获得其倍半二倍体。用充气液体培养基加８－羟基喹啉预处理，对不能以根尖为材料作染色体制片的植物，以其幼嫩花蕾进行体细胞染色体制片，对甘蓝型油菜与蓝花子属间倍半二倍体的细胞遗传学特性进行了研究，该植物的染色体数目为２ｎ＝４７。大多数ＰＭＣｓ的染色体在减数分裂过程中配对不规则，并在后期Ⅱ中出现多极分     

甘蓝型油菜与芝麻远缘杂交研究初报

采用植物远缘杂交新技术染色体段体杂交技术,以甘蓝型油菜品系HH2000-4、99-1253为授体,汉中本地芝麻为供体,将芝麻的染色体片段导入到甘蓝型油菜细胞中,使其与授体细胞的染色体发生染色体片段的重组和杂交,从而形成杂交染色体,并迅速分化发育成相应的杂交植物（芝麻-油菜）。本文通过对芝麻-油菜HN-1、HN-2、HN-3从生态学方面的研究观察表明3株芝麻-油菜与其授体亲本油菜在株高、分枝习性、植株形态、花器、角果等方面存在着明显的差异,初步判断已经将供体亲本的部分基因导入到授体亲本中。     

烟草花粉单倍体植株花粉母细胞减数分裂初步观察

对普通烟草(Nicotiana tabacum)的品种〔(临朐一号×佛及尼亚115)×柯克347〕杂交一代的花粉单倍体植株花粉母细胞的减数分裂,从细线期至花粉粒形成的过程作了观察。并用普通品种——红花大金元(双倍体)作比较。 单倍体植株和双倍体植株花粉母细胞减数分裂最显著区别之一是前者在前期Ⅰ粗线期时看不到同源染色体配对,终变期时绝大多数染色体为单价染色体,很少数是拟二价染色体,染色体有胶合,连结成各种形式,并有群聚现象。在单倍体植株的同一花药内,同时有染色体单倍数和很少量的双倍数的花粉母细胞。单倍体植株四分孢子形成后,细胞核在小孢子的进一步的发育中自行解体,成熟花粉粒一般没有生活力。     

水稻籼粳杂种多倍体的研究

以秋水仙碱诱导的水稻籼粳杂多倍体植株中，部分植株的体细胞呈现具有整倍体和非整倍体染色体数细胞嵌合现象，其中四倍体细胞最高可占35．3％，其余均为染色体数低于48条的各种细胞，与二倍体植株相比，这些植株的叶表皮气孔增大，气孔数减少，花粉粒直径增大都是十分显的，与多倍体植株无明显区别，并对这类植株根尖体细胞中存在具各种染色体数目细胞嵌合现象可能的原因进行了分析。     

Birth of parthenogenetic mice that can develop to adulthood

Only mammals have relinquished parthenogenesis, a means of producing descendants solely from maternal germ cells. Mouse parthenogenetic embryos die by day 10 of gestation. Bi-parental reproduction is necessary because of parent-specific epigenetic modification of the genome during gametogenesis. This leads to unequal expression of imprinted genes from the maternal and paternal alleles. However, there is no direct evidence that genomic imprinting is the only barrier to parthenogenetic development. Here we show the development of a viable parthenogenetic mouse individual from a reconstructed oocyte containing two haploid sets of maternal genome, derived from non-growing and fully grown oocytes. This development was made possible by the appropriate expression of the Igf2 and H19 genes with other imprinted genes, using mutant mice with a 13-kilobase deletion in the H19 gene as non-growing oocytes donors. This full-term development is associated with a marked reduction in aberrantly expressed genes. The parthenote developed to adulthood with the ability to reproduce offspring. These results suggest that paternal imprinting prevents parthenogenesis, ensuring that the paternal contribution is obligatory for the descendant.     

Sexual reproduction between partners of the same mating type in Cryptococcus neoformans

Cryptococcus neoformans is a globally distributed human fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised patients. It has a defined sexual cycle involving haploid cells of alpha and a mating types, yet the vast majority of environmental and clinical isolates are alpha (ref. 3). Sexual recombination is normally expected to occur between isolates of opposite mating type in organisms with two mating types (or sexes). How sexual reproductive potential can be maintained in an organism with a largely unisexual, nearly clonal population genetic structure is unknown. One clue, however, is that alpha strains undergo fruiting, a process that resembles sexual mating but is thought to be strictly mitotic and asexual. We report here that hallmarks of mating occur during fruiting, including diploidization and meiosis. Pheromone response pathway elements and the key meiotic regulator Dmc1 are required for efficient fruiting. Furthermore, fusion and meiosis can occur between non-isogenic alpha strains, enabling genetic exchange. These studies reveal how sexual reproduction can occur between partners of the same mating type. These findings have implications for the evolution of microbial pathogens, as well as for parthenogenesis, cell fusion events and transitions between self-fertilizing and outcrossing modes of reproduction observed in both fungi and other kingdoms.     

Essential role for de novo DNA methyltransferase Dnmt3a in paternal and maternal imprinting

Imprinted genes are epigenetically marked during gametogenesis so that they are exclusively expressed from either the paternal or the maternal allele in offspring. Imprinting prevents parthenogenesis in mammals and is often disrupted in congenital malformation syndromes, tumours and cloned animals. Although de novo DNA methyltransferases of the Dnmt3 family are implicated in maternal imprinting, the lethality of Dnmt3a and Dnmt3b knockout mice has precluded further studies. We here report the disruption of Dnmt3a and Dnmt3b in germ cells, with their preservation in somatic cells, by conditional knockout technology. Offspring from Dnmt3a conditional mutant females die in utero and lack methylation and allele-specific expression at all maternally imprinted loci examined. Dnmt3a conditional mutant males show impaired spermatogenesis and lack methylation at two of three paternally imprinted loci examined in spermatogonia. By contrast, Dnmt3b conditional mutants and their offspring show no apparent phenotype. The phenotype of Dnmt3a conditional mutants is indistinguishable from that of Dnmt3L knockout mice, except for the discrepancy in methylation at one locus. These results indicate that both Dnmt3a and Dnmt3L are required for methylation of most imprinted loci in germ cells, but also suggest the involvement of other factors.     

生物技术在果树学研究中的应用

主要对微繁殖、单倍体、胚培养、原生质体培养与体细胞杂交、基因转化及分子标记等技术在果树学研究中的应用进行了综述.     

Ethanol-induced chromosomal abnormalities at conception

Preliminary findings have indicated that mouse eggs exposed briefly in vivo or in vitro to a dilute solution of ethanol activate parthenogenetically. Cytogenetic analysis of the first-cleavage chromosomes of haploid parthenogenetic embryos indicated that up to 20% of this population were aneuploid as a result of non-disjunction. Anaesthetics also can induce parthenogenesis of rodent eggs, and in studies using anaesthetics, colchicine and colcemid, abnormal chromosome segregation and heteroploidy of rodent embryos have been observed. I now report that when recently mated female mice are given a dilute solution of ethanol by mouth, non-disjunction can be induced in the female-derived, but apparently not in the male-derived, chromosome set of fertilized eggs. Taken together, these findings suggest that ethanol consumption (as well as exposure to other 'spindle-acting' agents) at the time of conception may be the cause of certain types of chromosomal defects commonly observed in human spontaneous abortions.     

坛紫菜单性组织培养的性逆转研究

为了进一步研究坛紫菜的单性组织发育特征并验证其可能存在的单性生殖途径,本文对坛紫菜雌、雄营养细胞、组织发育过程中两性生殖组织的形成和繁殖特征以及两种单性遗传来源的子代叶状体的性别发育特征进行观察研究.结果表明,单性营养细胞和组织能够通过性逆转产生两性生殖组织并形成丝状体,该繁殖方式不属于单性生殖.单性遗传来源的子代叶状...     

Derivation of embryonic germ cells and male gametes from embryonic stem cells

Egg and sperm cells (gametes) of the mouse are derived from a founder population of primordial germ cells that are set aside early in embryogenesis. Primordial germ cells arise from the proximal epiblast, a region of the early mouse embryo that also contributes to the first blood lineages of the embryonic yolk sac. Embryonic stem cells differentiate in vitro into cystic structures called embryoid bodies consisting of tissue lineages typical of the early mouse embryo. Because embryoid bodies sustain blood development, we reasoned that they might also support primordial germ cell formation. Here we isolate primordial germ cells from embryoid bodies, and derive continuously growing lines of embryonic germ cells. Embryonic germ cells show erasure of the methylation markers (imprints) of the Igf2r and H19 genes, a property characteristic of the germ lineage. We show that embryoid bodies support maturation of the primordial germ cells into haploid male gametes, which when injected into oocytes restore the somatic diploid chromosome complement and develop into blastocysts. Our ability to derive germ cells from embryonic stem cells provides an accessible in vitro model system for studies of germline epigenetic modification and mammalian gametogenesis.     

Pathogen-induced systemic plant signal triggers DNA rearrangements

Plant genome stability is known to be affected by various abiotic environmental conditions, but little is known about the effect of pathogens. For example, exposure of maize plants to barley stripe mosaic virus seems to activate transposable elements and to cause mutations in the non-infected progeny of infected plants. The induction by barley stripe mosaic virus of an inherited effect may mean that the virus has a non-cell-autonomous influence on genome stability. Infection with Peronospora parasitica results in an increase in the frequency of somatic recombination in Arabidopsis thaliana; however, it is unclear whether effects on recombination require the presence of the pathogen or represent a systemic plant response. It is also not clear whether the changes in the frequency of somatic recombination can be inherited. Here we report a threefold increase in homologous recombination frequency in both infected and non-infected tissue of tobacco plants infected with either tobacco mosaic virus or oilseed rape mosaic virus. These results indicate the existence of a systemic recombination signal that also results in an increased frequency of meiotic and/or inherited late somatic recombination.     

烟草抗病基因源的利用与抗病育种策略

抗源选择是抗病育种的关键。野生和种间抗源的利用是目前和今后较长时间内烟草抗病育种的重要途径。体细胞杂交和体细胞无性系变异不仅丰富了烟草抗源的变异来源,而且使这些抗源易于操作和利用。配子体单克隆系变异与加倍单倍体的产生程序,以单倍体作为育种选择单位的技术,不仅选育出了含有新的抗病种质的品种(系),而且改进了抗病育种方法、并改变了抗病育种策略。新的抗病基因变异源的利用,对抗病性和产量、品质性状的同时改良,是今后烟草抗病育种必须达到的目标。     

Differential gene expression profiling in the developed ovaries between the parthenogenetic and bisexual female rice water weevils,Lissorhoptrus oryzophilus Kuschel （Coleoptera： Curculionidae）

The rice water weevil, Lissorhoptrus oryzophilus Kuschel （Coleoptera： Curculionidae）, reproduces by sex in the Southeastern United States, but reproduces by parthenogenesis in California and other invaded regions in Asia and Europe. The objective of this study was to create a parthenogenetic gene expression profile of the rice water weevil in order to gain a better insight into the molecular mechanisms of parthenogenesis in the weevil. Suppression subtractive hybridization （SSH） technique was employed for profiling differential gene expression in the developed ovary between the parthenogenetic and bisexual female rice water weevils. A total of 70 contigs were obtained, and the BLASTX search identified putatively 28 genes with differential functions. According to the cytological process of parthenogenesis, the tubulin alpha-1 chain and signal transduction genes etc. were selected for real time quantitative RT-PCR analyses, and their possible functions related to the molecular mechanism of parthenogenesis were discussed. The tubulin alpha-1 chain and some signal transduction genes may be related to the molecular mechanisms of parthenogenesis of the rice water weevil.