Selective sweeps of mitochondrial DNA can drive the evolution of uniparental inheritance

Although the uniparental (or maternal) inheritance of mitochondrial DNA (mtDNA) is widespread, the reasons for its evolution remain unclear. Two main hypotheses have been proposed: selection against individuals containing different mtDNAs (heteroplasmy) and selection against “selfish” mtDNA mutations. Recently, uniparental inheritance was shown to promote adaptive evolution in mtDNA, potentially providing a third hypothesis for its evolution. Here, we explore this hypothesis theoretically and ask if the accumulation of beneficial mutations provides a sufficient fitness advantage for uniparental inheritance to invade a population in which mtDNA is inherited biparentally. In a deterministic model, uniparental inheritance increases in frequency but cannot replace biparental inheritance if only a single beneficial mtDNA mutation sweeps through the population. When we allow successive selective sweeps of mtDNA, however, uniparental inheritance can replace biparental inheritance. Using a stochastic model, we show that a combination of selection and drift facilitates the fixation of uniparental inheritance (compared to a neutral trait) when there is only a single selective mtDNA sweep. When we consider multiple mtDNA sweeps in a stochastic model, uniparental inheritance becomes even more likely to replace biparental inheritance. Our findings thus suggest that selective sweeps of beneficial mtDNA haplotypes can drive the evolution of uniparental inheritance.     

Host nuclear genotype influences phenotype of a conditional mutualist symbiont

Arthropods commonly carry maternally inherited intracellular bacterial symbionts that may profoundly influence host biology and evolution. The intracellular symbiont Rickettsia sp. nr. bellii swept rapidly into populations of the sweetpotato whitefly Bemisia tabaci in the south‐western USA. Previous laboratory experiments showed female‐bias and fitness benefits were associated with Rickettsia infection, potentially explaining the high frequencies of infection observed in field populations, but the effects varied with whitefly genetic line. Here, we explored whether host extranuclear or nuclear genes influenced the variation in the Rickettsia–host phenotype in two genetic lines of the whitefly host, each with Rickettsia‐infected and uninfected sublines. Introgression between the Rickettsia‐infected subline of one genetic line and the Rickettsia‐uninfected subline of the other was used to create two new sublines, each with the maternally inherited extranuclear genetic lineages of one line (Rickettsia, two other symbionts and the mitochondria) and the nuclear genotype of the other. Performance assays comparing the original and new lines showed that in addition to Rickettsia, the interaction of Rickettsia infection with host nuclear genotype influenced development time and the sex ratio of the progeny, whereas the extranuclear genotype did not. Host nuclear genotype, but not extranuclear genotype, also influenced the titre of Rickettsia. Our results support the hypothesis that differences in host nuclear genotype alone may explain considerable within‐population variation in host–symbiont phenotype and may contribute to the observed variation in Rickettsia–whitefly interactions worldwide.     

不同生态环境下雌雄同株黄瓜单性结实性遗传的比较

以两个单性结实性不同的雌雄同株黄瓜自交系构建的4世代群体为试材,采用植物数量性状主基因+多基因混合遗传模型联合分析方法,对南京江宁和河北昌黎两地雌雄同株黄瓜单性结实性遗传进行了比较研究.结果表明：不同生态环境下,雌雄同株黄瓜单性结实性遗传均符合E-1-1模型,受2对加性-显性-上位性主基因+加性-显性多基因控制,存在基因型与环境互作效应.但是,不同环境条件下F₁的遗传倾向和遗传参数不同,F₂的主基因遗传率为42.1%～97.5%,其遗传差异主要由黄瓜结果期两地日照和温度差异所致.强单性结实黄瓜品种选育以双亲均为强单性结实材料为宜,杂种后代宜在不同生态条件下选择鉴定.     

基于线粒体COⅠ的DNA 条形码技术在贻贝科种类鉴定中的应用

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106例福建畲族男性Y染色体相对长度遗传性分析

人类Y染色体相对长度（Y/F值）在不同种族、不同人群中分布有明显差异,其与身高、生殖间的关系存在较大争议。本文通过对106例（53对父子）福建畲族男性Y/F值及身高的测量,揭示了福建畲族男性Y染色体相对长度在家系中具垂直遗传性,其大Y出现率为11.1%,居中等偏下水平。 Abstract:It is found that the distribution of Human Y chromosome relative length (Y/F) is different obviously within different ethnic and population.There are disputations on the relationship of Y/F with height and reproduction.By measuring the Y/F and height of 106 case (53 pairs of fathers and sons) of Fujian she ethnic,we can find that the Y chromosome relative length of Fujian she ethnic has plumb inheritance within pedigree and the appearance rate of long Y is 11.1%,below the medium level.     

蛋用鹌鹑伴性羽色基因互作与连锁的关系

本研究首次发现了鹌鹑伴性羽基因的基因互作关系并进行了遗传验证.试验证明,鹌鹑的栗羽、黄羽和白羽是Z染色体上两个有连锁关系的基因座B/b和Y/y相互作用的结果.B和b为一对等位基因,不控制任何性状,只与色素的合成有关,B为有色基因,b为白化基因,B对b为显性;Y和y为另一对等位基因,分别控制栗羽和黄羽,Y对y为显性.栗羽和黄羽的表现取决于有色基因B的存在,B与Y相互作用产生栗羽,B与y相互作用产生黄羽,白羽是白化基因b对Y和y上位作用的结果.B/b和Y/y两基因座在雄性表现出一定的互换率,在雌性为完全连锁.这一研究补充和发展了以前人们对鹌鹑羽色伴性遗传的研究,为人们利用鹌鹑羽色进行自别雌雄配套系生产提供了重要的遗传学基础。 Abstract:The interaction of sex-linked gene for plumage color in quails was first discovered and identified by genetictest.It was proved that the phenotypic expressions of the maroon feather,the yellow feather and the white feather result from the interaction between B/b and Y/y loci in the Z-chromosome.The allele B and b have something to do with the composition of pigment in plumage and nothing to do with any relative characters,the coloured gene B is dominant to its albino allele b.The maroon and yellow feather constituted a pair of relative characters determined by a couple of alleles Y and y,the maroon feather was caused by a dominant allele Y,and the yellow feather caused by a recessive allele y.But the phenotypic expression of maroon and yellow was decided by the present of the coloured gene B in Z-chromosome,the maroon feather was the result of interaction between gene B and Y,the yellow feather was result of interaction between gene B and y.The white was caused by a recessive albino gene b which epistasis to gene Y and y.The incomplete linkage was present between B/b and Y/y in Z-chromosome in male and complete linkage in female.This research enriches and delelops the earlier studies of the sex-linked inheritance of plumage color.It provides an important genetic basis for the quail autosexing system production by means of plumage color.     

油松细胞质遗传的细胞学机理：Ⅰ.雄配子的超微结构和细胞器类核

证明了油松（Ｐｉｎｕｓ ｔａｂｕｌａｅｆｏｒｍｉｓ Ｃａｒｒ．）雄配子存在质体物线粒体及细胞器ＤＮＡ,提供了油松具父系质体和线粒体遗传基础的确切的细胞学证据,结果与松科植物在遗传学上已确定的父系质体遗传的一般规律是一致的。但精细胞中的线粒体是否能传递至胚,还需要追踪其后的发育过程。另一重要的结果是揭示了油松的雄配子是细胞,这与以前将松科植物雄配子归入雄核（精核）的类型不同。精细胞无壁,仅被质膜包围     

油松细胞质遗传的细胞学机理:Ⅱ.雄性和雌性细胞器在受精和原胚时期的传递(英文)

在电镜下观察油松 (PinustabulaeformisCarr.)传粉后的胚珠临近受精时的花粉管和卵细胞的细胞质、受精时雄配子体细胞质的传递、游离核和细胞原胚发育时期质体和线粒体的传递。在成熟卵细胞中含许多线粒体 ,缺少正常结构的质体 ,它们转变为大内含体。此外 ,卵细胞还有丰富的小内含体和其他一些细胞器。花粉管在卵细胞的珠孔端释放其内含物。精核与卵核融合时 ,核周围未见来自精细胞的质体和线粒体。不参与融合的精核停留在接受液泡旁 ,在其周围有大量的雄性细胞质 ,其中混合有精细胞、管细胞和卵细胞的细胞器。在游离核原胚时期 ,核周区的细胞质中可见雄性与雌性亲本的细胞器相混合 ;其中许多线粒体与原来卵细胞中的线粒体有相同的形态 ,也有一些线粒体看来是来自精细胞和管细胞 ;质体是由雄配子体传递 ,形态与精细胞的或花粉管中的质体相似。卵细胞中变异的质体 (即大内含体 )在原胚发育时期变为液泡状 ,而雄性质体参加到新细胞质中。在原胚细胞中 ,线粒体大多数为母本来源 ,质体则表现为精细胞或管细胞的质体形态。该研究确定了油松具父系质体和双亲线粒体遗传的细胞学基础。对裸子植物线粒体和质体遗传的机理从细胞学的角度进行了分析。     

Production of transgenic tall fescue and red fescue plants by particle bombardment of mature seed-derived highly regenerative tissues

 Highly regenerative tissues of tall fescue and red fescue produced from mature seed-derived embryogenic callus were induced and proliferated on medium containing 2,4-dichlorophenoxyacetic acid (4.5 or 9.0 μM), 6-benzylaminopurine (0, 0.044, 0.44 or 2.2 μM) and cupric sulfate (0.1 or 5.0 μM) under dim-light conditions (10 to 30 μE m^–2 s^–1, 16 h light). Tall fescue tissues were transformed with three plasmids containing the genes for hygromycin phosphotransferase (hpt), phosphinothricin acetyltransferase (bar) and β-glucuronidase (uidA;gus), and red fescue with three plasmids containing hpt, uidA and a synthetic green fluorescent protein gene [sgfp(S65T)]. DNA from T₀ plants of eight independently transformed lines from tall fescue and 11 from red fescue were analyzed by PCR and DNA blot hybridization. The co-expression frequency of all three transgenes [hpt/bar/uidA or hpt/uidA/sgfp(S65T)] in transgenic tall fescue and red fescue plants was 25–27%; for two transgenes [hpt/bar or hpt/uidA for tall fescue and hpt/uidA or hpt/sgfp(S65T) for red fescue], the co-expression frequency was 50–75%. Received: 28 September 1999 / Revision received: 13 March 2000 / Accepted: 16 March 2000     

基因枪法转基因水稻中hpt基因稳定遗传

基因枪转化将潮霉素磷酸转移酶基因（ｈｐｔ）导入粳稻品种７７１７０,获得可育的转基因植株,研究外源基因遗传的稳定性。自交后代（Ｔ１和Ｔ２）经潮霉素筛选获得抗性植株和敏感植株,分子鉴定结果表明抗性植株带有ｈｐｔ基因,而敏感植株中没有ｈｐｔ基因存在。Ｔ１和Ｔ２代中潮霉素抗性表现为显性单基因位点的遗传方式,符合孟德尔分离规律,并得到分子鉴定结果的证实。Ｓｏｕｔｈｅｒｎ杂交结果显示,ｈｐｔ基因多拷贝整合在水