中国东北地区黑腹果蝇（Drosophila melanogaster）P因子分布和来源

真核生物的转座因子(transposable elements)特别是果蝇P因子在研究生物进化上有重要的意义。以我国东北地区13个地方及毗邻的北京、烟台和呼和浩特三个地方共130个黑腹果蝇(D.melanogaster)单雌系为材料,对P因子序列的ORF2-ORF3区段进行PCR扩增,统计不同地方黑腹果蝇群体的P因子在此区段的缺失频率,再从整个地区来分析P因子缺失的分布规律,以推导东北地区黑腹果蝇中P因子的传递和扩散途径。结果显示P因子缺失频率由边境地区向内地逐渐递减,群体相对隔离的地方也较低,推断我国东北地区黑腹果蝇中P因子由朝鲜和俄罗斯向中国边境入侵后,逐步向中国内地扩散。     

中国东北地区黑腹果蝇(Drosophila melanogaster)P因子分布和来源

真核生物的转座因子(transposable elements)特别是果蝇P因子在研究生物进化上有重要的意义。以我国东北地区13个地方及毗邻的北京、烟台和呼和浩特三个地方共130个黑腹果蝇(D.melanogaster)单雌系为材料,对P因子序列的ORF2-ORF3区段进行PCR扩增,统计不同地方黑腹果蝇群体的P因子在此区段的缺失频率,再从整个地区来分析P因子缺失的分布规律,以推导东北地区黑腹果蝇中P因子的传递和扩散途径。结果显示P因子缺失频率由边境地区向内地逐渐递减,群体相对隔离的地方也较低,推断我国东北地区黑腹果蝇中P因子由朝鲜和俄罗斯向中国边境入侵后,逐步向中国内地扩散。     

我国大陆部分地区黑腹果蝇群体线粒体DNA多态性研究

用１０种限制性内切酶对我国大陆５个地方（武汉,长沙,桂林,南宁和北海）６个黑腹果蝇（Ｄｒｏｓｏｐｈｉｌａｍｅｌａｎｏｇａｓｔｅｒ）群体的线粒体ＤＮＡ进行了限制片段长度多态性分析,在５６个单雌系中,发同了２５种不同的限制类型,应用Ｎｅｉ等（１９７９）的数学模型和ＵＰＧ法,构建了限制类型间和群体间的系统进化树,结果发现：所研究的群体分为３个类群,对应于南,中和北３个亚热带地区,除长沙玉合醋厂外,所有采     

中国银额果蝇自然群体B染色体的分布

经对我国银额果蝇自然群体Ｂ染色体（Ｂｓ）的分布进行多年广泛地调查,共作过２４个群体,５７２个单雌系,６７３８只个体的观察。从细胞和群体水平研究Ｂｓ的地理分布。结果发现,中国（除台湾省外）银额果蝇自然群体中普遍存在Ｂｓ。结合前人报道得出。Ｂｓ的地理分布出现了由东向西和由南向北的规律性的依次升高趋势。这种跨越不同地理环境的区域性梯度变异与其宿主向大陆内地扩散的推论相符。Ｂｓ频率最高（８７．７％）的是海     

中国大陆若干群体的黑果蝇的线粒体DNA多态性研究

本文研究了果蝇Ｄ．ｖｉｒｉｌｉｓ种群Ｄ．ｖｉｒｉｌｉｓ线粒体ＤＮＡ（ｍｉｔｏｃｈｏｎｄｒｉａｌＤＮＡ,ｍｔＤＮＡ）的多态性。用９种限制性内切酶ＸｂａⅠ,ＥｃｏＲⅠ,ＰｓｔⅠ,ＨｉｎｄⅢ,ＢｇｌⅡ,ＳａｃⅠ,ＳｃａⅠ,ＥｃｏＲＶ和ＰｕｖⅡ,对青岛、南京、上海、宁波与泉州５个Ｄ．ｖｉｒｉｌｉｓ群体的ｍｔＤＮＡ进行了限制性片段长度多态性（ｒｅｓｔｒｉｃｔｉｏｎｆｒａｇｍｅｎｔｓｌｅｎｇｔｈｐｏｌｙｍｏｒｐｈｉｓｍ,ＲＦＬＰ）的研究。在５群体中,发现５种不同的酶切图谱,它们彼此之间的遗传差异π为０．４６％－１．７６％,群体内遗传差异πｉｊ为０．００％－０．３３％,群体间的差异ｄｘｙ,为０．００％－０．８２％。分布于中国大陆的Ｄ．ｖｉｒｉｌｉｓ的群体间遗传差异在总遗传差异中所占比例γｓｔ值为２４．６２％。我们发现,Ｄ．ｖｉｒｉｌｉｓ的栖息环境对ｍｔＤＮＡ的遗传变异有十分明显的影响,而不同地理纬度的群体之间其遗传距离并无倾群（ｃｌｉｎｅ）表现。     

我国三地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响

【目的】Wolbachia 是广泛存在于节肢动物和丝状线虫体内的一类共生菌, 能够以多种方式对宿主产生影响。精卵细胞质不亲和（CI）是其引起的最普遍的表型, 即感染Wolbachia的雄性宿主与未感染或感染不同品系的雌性宿主交配后, 不能产生后代或后代极少, 而感染同品系Wolbachia的雌雄宿主交配后则能正常产生后代。我们前期研究发现, 湖北武汉、 云南六库和天津3个地区黑腹果蝇Drosophila melanogaster被Wolbachia感染。本研究旨在明确这3个地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响。【方法】利用Clustal X软件对Wolbachia的wsp基因序列进行比对, 利用MEGA软件构建系统发育树。采用多位点序列分型（MLST）的方法对Wolbachia进行分型。通过区内交配和区之间杂交的方式研究不同地区黑腹果蝇体内Wolbachia 的关系及其对果蝇生殖的影响。【结果】湖北武汉、 云南六库和天津3个地区黑腹果蝇中感染的Wolbachia都是属于A大组的Mel亚群。这3个地区果蝇感染的Wolbachia的序列类型（ST）不同, Wolbachia之间存在一定的差异。湖北武汉和天津果蝇中的Wolbachia能引起强烈的CI表型, 而云南六库果蝇中的Wolbachia引起的CI强度相对较弱。武汉果蝇中Wolbachia不能完全挽救天津果蝇中Wolbachia引起的CI表型, 而天津果蝇中Wolbachia也不能完全挽救武汉果蝇中Wolbachia引起的CI表型。【结论】武汉和天津地区黑腹果蝇中的Wolbachia可能距离较远。Wolbachia的长期共生可能对黑腹果蝇的进化产生了一定的影响, 湖北武汉与云南六库的黑腹果蝇中感染的Wolbachia属于不同的序列类型, 这2个地区的黑腹果蝇已发生了一定的分歧, 产生了一定的生殖隔离。     

横断山地区果蝇三新种(双翅目：果蝇科)

横断山地区果蝇三新种（双翅目：果蝇科）张文霞,梁醒财（北京大学生命科学学院北京１００８７１）（中国科学院昆明动物研究所昆明６５０２２３）’果蝇属果蝇亚属Ｄｒｏｓｏｐｈｉｌａ（Ｄｒｏｓｏｐｈｉｌａ）的ｍｅｌａｎｄｅｒｉ种组由Ｗｈｅｅｌｅｒ１９４９年建立...     

用ＰＣＲ—ＳＳＯ方法研究云南西部彝族ＨＬＡ—ＤＱＢ１基因的多态性

应用ＰＣＲ－ＳＳＯ基因分型技术,对我国云南西部地区３代内无血缘关系的７６个彝族健康个体进行了ＬＡ－ＤＱＢ１位点的基因分型。结果显示,在ＤＱＢ１的３８个等位基因中,观察到１３个等位基因,云南西彝族表现为ＤＱＢ１＊０３０１（３６．１８％－３６．８４％）最常见。其他频率大于５％的等位基因还有ＤＱＢ１＊０５０２（１０．５３％－１１．１８％）、ＤＱＢ１＊０４０１（９．２１％）、ＤＱＢ１＊０３０２（８．５５％－９．２１％）、ＤＱＢ１*0601(7．８９％）ＤＱＢ１＊０５０３１（６．５８％）、ＤＱＢ１＊０３０３２（５．９２％－６．５８％）。和其他１３个华人群体ＤＱＢ１等位基因的频率比较分析表明,总体上,云南西彝族和其他各华人群体间都存在很大的差异。显示其ＨＬＡ等位基因频率分布的民族独特性。     

黑腹果蝇的分离变相因子

众所周知,一对基因在杂合状态中保持相对的独立性,而在配子形成时,又按原样以相同比例分离到不同的配子中去,这是生物中最基本的遗传规律———孟德尔分离定律。但实际上并不是所有基因的分离都严格遵循孟德尔分离定律,存在于黑腹果蝇中的分离变相因子（ＳｅｇｒｅｇａｔｉｏｎＤｉｓｔｏｒｔｅｒ,以下简称ＳＤ）就是一种具有减数分裂驱动（ｍｅｉｏｔｉｃｄｒｉｖｅ）性质的、违反孟德尔分离定律的特殊遗传因子,从六十年代发现至今引起了人们的广泛关注,本文从其遗传背景,结构特征及进化规律等方面分别介绍一些近期的研究结果。１…     

中国大陆部分地区Drosophila immigrans果蝇种群中mtDNA的遗传多态？…

选用１４种限制性内切酶分布在中国大陆部分地区的Ｄｒｏｓｏｐｈｉｌａｉｍｍｉｇｒａｎｓ果蝇种群的线粒体ＤＮＡ（ｍｔＤＮＡ）限制性片段长度多态性（ＲＦＬＰ）进行了分析,在６个地理种群的４６例单雌系中仅检测到１１种限制性类型,表征种群内均一程度的Ｉ值平均为０．８３３,衡量种群间等同程度的Ｊ值平均为０．７９７,在整个种群中只有１６．８％（Ｇｓｔ）的变异是由种群间变异所引起的,说明分布在中国大陆部分地区的Ｄ     

Further genetic studies on the Katsunuma population of Drosophila melanogaster

Changes in the genetic structure of the Katsunuma natural population of Drosophila melanogaster have been examined during the past 35 years. The frequency of recessive lethal genes on the second chromosome once increased from 15% to 30% in the early 1970s, then decreased to about 24% in the late 1970s, and thereafter showed no significant changes. Sterility genes, the frequency of which is always less than the lethals, showed a similar tendency. The SD (segregation distorter) mutant gene disappeared but some others such as rbl (reduced bristle) and bw (brown) persisted in the population. The frequency of inversion-carrying chromosomes gradually decreased in the period, such that the standard chromosome frequency in the second and third chromosomes increased from about 40% to more than 80%. Coincident with these frequency changes is the invasion of a transposable element P into the Katsunuma population. The P element should have invaded into Katsunuma in the late 1960s. It spread over the population apparently inducing deleterious mutations, causing the decrease in the allelism rate, and hence increasing the effective population size. Soon, however, most flies became resistant to the P element-mediated transposition as they began to harbor defective P elements. During the course of spreading, the P element must also have induced deleterious mutations on the polymorphic inversions, breaking up the heterotic gene complexes along the chromosomes, which probably caused the reduction in the frequency of inversion chromosomes. Temporal invasion of D. simulans, a sibling species of D. melanogaster, into Katsunuma occurred several times after 1978, and the species seems to have been settled since 1990. This, however, did not have any effect on the genetic structure of D. melanogaster population.     

Factors Influencing the Effect of Segregation Distortion in Natural Populations of DROSOPHILA MELANOGASTER

The major components of the SD system have been examined in two natural populations of D. melanogaster to investigate how SD behaves and is maintained in nature and to estimate its impact and efficiency. A twofold approach was used: (1) direct measurements of segregation distortion in wild males and (2) measurement of sensitivity of wild SD (+) chromosomes to SD action. Characterization of newly isolated SD chromosomes and of a large number of SD( +) chromosomes from nature demonstrated that (1) SD can operate efficiently in the wild genome: 45% of SD/SD(+) males collected from nature had k values larger than 0.70. (2) Forty-three of 44 newly recovered SD chromosomes are of the SD-72 type, having a small pericentric inversion that maintains tight linkage among the Sd, E(SD) and Rsp loci in the SD complex. In 1956, most SD chromosomes in Madison lacked this inversion. (3) Only 12 of the 44 SD chromosomes carried a recessive lethal (compared with five of six in 1956), and many of the viable SD chromosomes were fertile as homozygotes, indicating that SD homozygotes need not have obvious reductions in fitness. (4) Among more than 500 wild chromosomes assayed for response to distortion by a strong SD, at least 40-50% were sensitive, about 33% were partially sensitive and 17% were insensitive. This frequency of sensitives is higher than in reports from some other populations. An estimated 12% of the wild chromosomes were classified as true Rsp(i) by their constellation of effects, including a special test of ability to cause self-distortion of a "suicide" chromosome, R(cn)-10. In a direct assay with R(cn)-10, an independent sample of 99 chromosomes from nature gave 30% putative Rsp(i). Thus, these populations contain in the range of 12-30% Rsp(i). (5) Chromosomes supersensitive to SD, previously described for certain laboratory stocks, were also found to coexist in nature with SD. (6) Profiles of wild chromosomes with a panel of three or four different SD testers suggest a series of allelic alternatives at the Rsp locus including supersensitive, sensitive, semisensitive and insensitive, and that loci other than Rsp may also be important in determining the effect of SD in nature.     

A Reanalysis of Protein Polymorphism in Drosophila Melanogaster, D. Simulans, D. Sechellia and D. Mauritiana: Effects of Population Size and Selection

Comparison of synonymous and nonsynonymous variation/substitution within and between species at individual genes has become a widely used general approach to detect the effect of selection versus drift. The sibling species group comprised of two cosmopolitan (Drosophila melanogaster and Drosophila simulans) and two island (Drosophila mauritiana and Drosophila sechellia) species has become a model system for such studies. In the present study we reanalyzed the pattern of protein variation in these species, and the results were compared against the patterns of nucleotide variation obtained from the literature, mostly available for melanogaster and simulans. We have mainly focused on the contrasting patterns of variation between the cosmopolitan pair. The results can be summarized as follows: (1) As expected the island species D. mauritiana and D. sechellia showed much less variation than the cosmopolitan species D. melanogaster and D. simulans. (2) The chromosome 2 showed significantly less variation than chromosome 3 and X in all four species which may indicate effects of past selective sweeps. (3) In contrast to its overall low variation, D. mauritiana showed highest variation for X-linked loci which may indicate introgression from its sibling, D. simulans. (4) An average population of D. simulans was as heterozygous as that of D. melanogaster (14.4% v.s. 13.9%) but the difference was large and significant when considering only polymorphic loci (37.2% v.s. 26.1%). (5) The species-wise pooled populations of these two species showed similar results (all loci = 18.3% v.s. 20.0%, polymorphic loci = 47.2% v.s. 37.6%). (6) An average population of D. simulans had more low-frequency alleles than D. melanogaster, and the D. simulans alleles were found widely distributed in all populations whereas the D. melanogaster alleles were limited to local populations. As a results of this, pooled populations of D. melanogaster showed more polymorphic loci than those of D. simulans (48.0% v.s. 32.0%) but the difference was reduced when the comparison was made on the basis of an average population (29.1% v.s. 21.4%). (7) While the allele frequency distributions within populations were nonsignificant in both D. melanogaster and D. simulans, melanogaster had fewer than simulans, but more than expected from the neutral theory, low frequency alleles. (8) Diallelic loci with the second allele with a frequency less than 20% had similar frequencies in all four species but those with the second allele with a frequency higher than 20% were limited to only melanogaster the latter group of loci have clinal (latitudinal) patterns of variation indicative of balancing selection. (9) The comparison of D. simulans/D. melanogaster protein variation gave a ratio of 1.04 for all loci and 1.42 for polymorphic loci, against a ratio of approximately 2-fold difference for silent nucleotide sites. This suggests that the species ratios of protein and silent nucleotide polymorphism are too close to call for selective difference between silent and allozyme variation in D. simulans. In conclusion, the contrasting levels of allozyme polymorphism, distribution of rare alleles, number of diallelic loci and the patterns of geographic differentiation between the two species suggest the role of natural selection in D. melanogaster, and of possibly ancient population structure and recent worldwide migration in D. simulans. Population size differences alone are insufficient as an explanation for the patterns of variation between these two species.     

World-wide survey of an Accord insertion and its association with DDT resistance in Drosophila melanogaster

Previous work showed that insecticide resistance in Drosophila melanogaster is correlated with the insertion of an Accord-like element into the 5' region of the cytochrome P450 gene, Cyp6g1. Here, we study the distribution of the Accord-like element in 673 recently collected D. melanogaster lines from 34 world-wide populations. We also examine the extent of microsatellite variability along a 180-kilobase (kb) genomic region of chromosome II encompassing the resistance gene. We confirm a 100% correlation of the Accord insertion with insecticide resistance and a significant reduction in variability extending at least 20 kb downstream of the Cyp6g1 gene. The frequency of the Accord insertion differs significantly between East African (32-55%) and nonAfrican (85-100%) populations. This pattern is consistent with a selective sweep driving the Accord insertion close to fixation in nonAfrican populations as a result of the insecticide resistance phenotype it confers. This study confirms that hitchhiking mapping can be used to identify beneficial mutations in natural populations.     

Genetic Load in Natural Populations: Is It Compatible with the Hypothesis That Many Polymorphisms Are Maintained by Natural Selection?

Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.     

The recent spread of a vertically transmitted virus through populations of Drosophila melanogaster

The sigma virus is a vertically transmitted pathogen that commonly infects natural populations of Drosophila melanogaster. This virus is the only known host-specific pathogen of D. melanogaster, and so offers a unique opportunity to study the genetics of Drosophila-viral interactions in a natural system. To elucidate the population genetic processes that operate in sigma virus populations, we collected D. melanogaster from 10 populations across three continents. We found that the sigma virus had a prevalence of 0-15% in these populations. Compared to other RNA viruses, we found that levels of viral genetic diversity are very low across Europe and North America. Based on laboratory measurements of the viral substitution rate, we estimate that most European and North American viral isolates shared a common ancestor approximately 200 years ago. We suggest two explanations for this: the first is that D. melanogaster has recently acquired the sigma virus; the second is that a single viral type has recently swept through D. melanogaster populations. Furthermore, in contrast to Drosophila populations, we find that the sigma viral populations are highly structured. This is surprising for a vertically transmitted pathogen that has a similar migration rate to its host. We suggest that the low structure in the viral populations can be explained by the smaller effective population size of the virus.     

Nonneutral admixture of immigrant genotypes in African Drosophila melanogaster populations from Zimbabwe

Drosophila melanogaster originated in Africa and colonized the rest of the world only recently (approximately 10,000 to 15,000 years ago). Using 151 microsatellite loci, we investigated patterns of gene flow between African D. melanogaster populations representing presumptive ancestral variation and recently colonized European populations. Although we detected almost no evidence for alleles of non-African ancestry in a rural D. melanogaster population from Zimbabwe, an urban population from Zimbabwe showed evidence for admixture. Interestingly, the degree of admixture differed among chromosomes. X chromosomes of both rural and urban populations showed almost no non-African ancestry, but the third chromosome in the urban population showed up to 70% of non-African alleles. When chromosomes were broken into contingent microsatellite blocks, even higher estimates of admixture and significant heterogeneity in admixture was observed among these blocks. The discrepancy between the X chromosome and the third chromosome is not consistent with a neutral admixture hypothesis. The higher number of European alleles on the third chromosome could be due to stronger selection against foreign alleles on the X chromosome or to more introgression of (beneficial) alleles on the third chromosome.