Simulation of gene pyramiding in Drosophila melanogaster

Gene pyramiding has been successfully practiced in plant breeding for developing new breeds or lines in which favorable genes from several different lines were integrated.But it has not been used in animal breeding,and some theoretical investigation and simulation analysis with respect to its strategies,feasibility and efficiency are needed before it can be implemented in animals.In this study,we used four different pure lines of Drosophila melanogaster,each of which is homozygous at a specific mutant gene ...     

Differential requirements for the neurogenic gene almondex during Drosophila melanogaster development

During early development, the neurogenic genes of Drosophila melanogaster are involved in the control of cell fates in the neurectoderm; almondex (amx) belongs to this category of genes. We have identified the amx locus and rescued the amx embryonic neurogenic phenotype with a 1.5 kb DNA fragment. Using a small deficiency, we generated a new amx mutant background called amx(m), which is a null allele. Besides the characteristic neurogenic maternal effect caused by loss of amx, amx(m) flies display a new imaginal phenotype resembling loss of function of Notch. We describe amx-induced misregulation of the Notch pathway target E(spl) m7 in embryos and genetic interactions between amx and Notch pathway mutants in adult flies. These data show that wildtype amx acts as a novel positive regulator of the Notch pathway and is required at different levels during development.     

Evidence of gene conversion associated with a selective sweep in Drosophila melanogaster

Since Drosophila melanogaster colonized Europe from tropical Africa 10 to 15 thousand years ago, it is expected that adaptation has played a major role in this species in recent times. A previously conducted multilocus scan of noncoding DNA sequences on the X chromosome in an ancestral and a derived population of D. melanogaster revealed that some loci have been affected by directional selection in the European population. We investigated if the pattern of DNA sequence polymorphism in a region surrounding one of these loci can be explained by a hitchhiking event. We found strong evidence that the studied region around the gene unc-119 was shaped by a recent selective sweep, including a valley of reduced heterozygosity of 83.4 kb, a skew in the frequency spectrum, and significant linkage disequilibrium on one side of the valley. This region, however, was interrupted by gene conversion events leading to a strong haplotype structure in the center of the valley of reduced variation.     

黑腹果蝇的性别控制

性别的形成包括两个过程,即性别决定和性别分化。果蝇的性别控制研究包括性别决定、性别分化、性别鉴定、性别诱导和性别控制5个方面。性别决定是在两种不同发育途径之间的选择,它提供了一个研究基因调控的模式系统。果蝇的性别决定问题已经研究得相当详细［1］。性别分化是使胚胎向着雌性或雄性发育的过程,决定了性别表型。果蝇的性别分化也取得了不少研究成果。近年来,许多重要的性别调控基因已被克隆和鉴定。随着果蝇基因组全序列测定的完成,果蝇的性别控制研究将会更为深入而完善。本文对与黑腹果蝇性别决定和性别分化相关的一些问题进行综述。     

Cytological location and further characterization of the Third chromosome resistance gene in Drosophila melanogaster

Mutations in the Third chromosome resistance (Tcr; 3-39.6) gene confer dominant resistance to α-methyl dopa and suggest the gene is involved in catecholamine metabolism. Evidence for involvement in catecholamine metabolism comes from the three phenotypes associated with the mutant Tcr chromosomes dominant resistance, dominant rescue of partially complementing l(2)amd alleles, and recessive lethal phenotypes. Only dominant resistance to αs-methyl dopa, however, was mapped to the Tcr locus. Both recessive lethality and dominant rescue of l(2)amd alleles have now been mapped to the Tcr gene and, through the isolation of a new deletion in the region, we demonstrate these phenotypes are due to a loss of Tcr function. This deletion places the Tcr gene in the 69B4-5 to 69C8-11 region. Additionally, we have tested and verified three predictions of the biochemical model proposed by Bishop, Sherald, and Wright (1989) for the function of the Tcr protein. This revised version was published online in July 2006 with corrections to the Cover Date.     

Age-dependent behavior loss in adult Drosophila melanogaster

The use of Drosophila as an organism in which to study aging has been limited by the fact that few biomarkers of aging exist in the adult. In this paper we examine behavior loss relative to longevity in wild-type populations maintained at 22°C and 29°C to determine whether behavior loss—that is, loss of ability to perform certain innate behavioral responses within a defined test interval—can be used as biomarkers of aging. We find that under controlled conditions behavior loss can be used as a landmark of aging in populations maintained at either 22°C or 29°C. The ability to perform normal geotactic and phototactic responses is lost during the reproductive phase of the adult populations, whereas motor activity is not lost until well into the death phase. We feel that the use of behavior loss, together with other parameters of longevity in Drosophila, will allow comparisons to be made between different strains or between different environmental conditions to test their effect on aging. In the companion paper we demonstrate the use of behavior loss to identify a mutation which may accelerate the aging process.     

果蝇衰老的调控机制

衰老是一个复杂的生物学过程,涉及到有害物质的积累导致整体生命功能的下降,生物的生理状况逐渐恶化,最终导致疾病和死亡。黑腹果蝇Drosophila melanogaster作为最重要的遗传学工具之一,近年来常被用于衰老的研究,以阐明衰老的发生与发展机制。本文结合本实验室的研究进展,综述了果蝇寿命调控的生理生化机制,如保幼激素、胰岛素/类胰岛素生长因子、TOR信号网络、腺苷酸活化蛋白激酶信号通路、热量限制和饮食限制、氧化应激、小分子RNA以及鞘脂类代谢都会对果蝇的寿命产生影响。除此之外,基因调控网络研究还能够发现潜在的与长寿相关的基因组区域,将有可能发现更多寿命相关基因。以果蝇为模式生物的研究,对于其他昆虫衰老、存活等种群生物学问题的研究以及天敌、益虫保育和害虫控制,具有十分重要的指导意义。     

不同温度条件下果蝇染色体结构的变化

将黑腹果蝇Drosophila melanogaster置于不同温度环境下培养,应用改良苯酚品红染色法制片.发现其唾腺染色体在不同的温度培养条件下,分布于染色体上的膨松区域有明显变化,在15℃和27℃下染色体的变化区域明显较19℃和23℃下的多,这些区域都与机体调控和表达的基因相关.这可能是机体对不适生存条件采取的保护措施所引起更多的染色体或基因发生变化的结果.对不同温度条件下部分染色体膨松区域的特殊基因作了简单讨论.     

Habitat selection by Drosophila melanogaster larvae

Drosophila melanogaster larvae are used to examine habitat choice behavior and its effect on a component of preadult fitness (pupal survivorship). We established strains of flies by collecting pupae from two microhabitats from an orchard. Strain differences in pupation site choice (on versus off fruit) persisted in a field-like laboratory assay without artificial selection. To produce heterogeneous environments, air temperature and soil water content were varied in these assays. A habitat suitability difference measure was used to determine for each environment, which microhabitat (on or off fruit) resulted in greater pupal survivorship. We found 1) that habitat choice behavior had both plastic and heritable components, 2) that strain-by-environment interactions influenced habitat choice behavior and pupal survivorship and, 3) a significant positive correlation between habitat suitability and larval habitat choice behavior.     

Targeted gene disruption by CRISPR/xCas9 system in Drosophila melanogaster

Although the Cas9 protein from Streptococcus pyogenes (SpCas9) is the most widely used clustered regularly interspaced short palindromic repeats (CRISPR) variant in genome engineering experiments, it does have certain limitations. First, the stringent requirement for the protospacer adjacent motif (PAM) sequence limits the target DNA that can be manipulated using this method in insects. Second, its complementarity specifications are not very stringent, meaning that it can sometimes cause off-target effects at the target site. A recent study reported that an evolved SpCas9 variant, xCas9(3.7), with preference for various 5′-NG-3′ PAM sequences not only has the broadest PAM compatibility but also has much greater DNA specificity and lower genome-wide off-target activity than SpCas9 in mammalian cells. Here we applied the CRISPR/xCas9 system to target the white gene in Drosophila melanogaster, testing the genome-editing efficiency of xCas9 at different PAM sites. On the GGG PAM site, xCas9 showed less activity than SpCas9. For the non-NGG PAM site TGA, xCas9 could produce DNA cleavage and indel-mediated disruption on the target gene. However, for other non-NGG PAM sites, xCas9 showed no activity. These findings show that the evolved Cas9 variant with broad PAM compatibility is functional in Drosophila to induce heritable gene alterations, increasing the targeting range for the applications of genome editing in insects.     

杂交群体动物基因聚合

基因聚合是通过优化设计杂交方案,选择利用目标基因或与其紧密连锁的分子标记,通过世代选择实现将来源于多个不同群体的优势目标基因或基因型聚合到同一个理想个体中,进而达到生产出超级经济性状个体的目的。针对聚合不同目标基因个数,设计4类杂交方案——两群体、三群体、四群体级联、四群体对称。在相同的杂交方案中,比较基因型选择和表型选择策略,分析不同杂交组合、性状遗传力、初始基因频率、基础群体规模对聚合设计的影响,并筛选出最佳的聚合方案。研究结果表明,在较大的基础群体规模和较高初始群体基因频率下,获得聚合多个目标基因的理想个体的可能性较大。在四群体杂交方案中,亲本的杂交次序对于级联杂交比对称杂交的影响较大。模拟结果表明,运用基因型选择进行聚合育种优于表型选择。文章所开发设计的聚合模拟育种的统计分析方法和相应软件为指导杂交育种方案和选择策略的设计提供理论参考,同时,为进一步设计开发聚合设计模拟育种平台奠定基础。     

Origin,evolution, and population genetics of the selfish Segregation Distorter gene duplication in European and African populations of Drosophila melanogaster

Meiotic drive elements are a special class of evolutionarily “selfish genes” that subvert Mendelian segregation to gain preferential transmission at the expense of homologous loci. Many drive elements appear to be maintained in populations as stable polymorphisms, their equilibrium frequencies determined by the balance between drive (increasing frequency) and selection (decreasing frequency). Here we show that a classic, seemingly balanced, drive system is instead characterized by frequent evolutionary turnover giving rise to dynamic, rather than stable, equilibrium frequencies. The autosomal Segregation Distorter (SD) system of the fruit fly Drosophila melanogaster is a selfish coadapted meiotic drive gene complex in which the major driver corresponds to a partial duplication of the gene Ran‐GTPase activating protein (RanGAP). SD chromosomes segregate at similar, low frequencies of 1–5% in natural populations worldwide, consistent with a balanced polymorphism. Surprisingly, our population genetic analyses reveal evidence for parallel, independent selective sweeps of different SD chromosomes in populations on different continents. These findings suggest that, rather than persisting at a single stable equilibrium, SD chromosomes turn over frequently within populations.     

中国黑腹果蝇种组40种果蝇的核型多样性研究

通过传统的敲片、Giemsa染色的方法制片对中国黑腹果蝇种组(Drosophilamelanogasterspeciesgroup)8个种亚组40种果蝇的染色体进行了分析,共发现18种核型,即A、A′′、C、C′、C′′、C′′′、C′′′′、D、D′、D′′、E、E′、E′′、F、F′、G、H和I,其中A、A′′、C′′′、C′′′′、D′′和F′为新发现的核型。8个种亚组的基本核型分别是:嗜凤梨果蝇种亚组(D.ananassaesubgroup)的核型为F、F′、G和H型;牵牛花果蝇种亚组(D.eleganssubgroup)的核型为A和A′′型;细针果蝇种亚组(D.eugracilissubgroup)的核型为C型;嗜榕果蝇种亚组(D.ficusphilasubgroup)的核型为C′型;黑腹果蝇种亚组(D.melanogastersubgroup)的核型为C和C′型;山果蝇种亚组(D.montiumsubgroup)的核型为C、C′、C′′、D、D′、D′′、E、E′、E′′和I型;铃木氏果蝇种亚组(D.suzukiisubgroup)的核型为C′′′和C′′′′型;高桥氏果蝇种亚组(D.takahashiisubgroup)的核型为C、C′′′和C′′′′型。透明翅果蝇(D.lucipennis)雌性核型2n=8,雄性核型2n=7,雄性Ⅳ号染色体为染色体单体。此外还发现,吉川氏果蝇(D.kikkawai)、林氏果蝇(D.lini)、奥尼氏果蝇(D.ogumai)、拟嗜凤梨果蝇(D.pseudoananassae)和叔白颜果蝇(D.triauraria)5种果蝇有B染色体。本文确定了D.sp.likeelegans、D.sp.likenyinyii、D.sp.liketrapezifrons1、D.sp.liketakahashii、D.sp.liketrapezifrons2和D.sp.likeauraria等6个未描述种的核型和1个新记录种吉里果蝇(D.giriensis)的核型。本研究证明了在黑腹果蝇种组内、亚组内、种内和单雌系内的核型多样性,为果蝇遗传和进化提供了进一步的细胞学证据。     

紫外线对黑尾果蝇的生物学效应

野生型黑尾果蝇经紫外线连续处理3代,随着照射时间延长,每代均表现显著的生物学效应。这些生物学效应主要是子代数量减少,羽化延续时间缩短,体重减轻,而且有致略效应和间接的诱变效应。但处理后的子代性别比例变化不大。     

黑腹果蝇white基因在H_2O_2影响下卷翅形成中的作用及机理

卷翅是果蝇遗传学上最常用的标记之一,但卷翅形成的具体机制还不清楚.过去的研究发现,理化刺激影响果蝇卷翅的形成.我们最近研究发现,H_2O_2处理不仅会影响果蝇的羽化率,还会使其出现卷翅现象.本研究通过改变H_2O_2浓度、果蝇培养温度和H_2O_2处理时间,探讨影响黑腹果蝇卷翅形成的具体因素,并对其超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GSH-PX)活力进行检测,探讨H_2O_2对果蝇抗氧化能力的影响.结果表明:果蝇的羽化率与H_2O_2浓度成反比.温度、H_2O_2浓度和H_2O_2处理时间的改变均会影响果蝇翅的卷曲程度和卷翅果蝇所占的比例.其中white基因突变果蝇对这3种条件反应最明显,mini-white(white基因回复突变)果蝇却可以拯救该表型,它的反应与野生型OR相似.H_2O_2对含Cy基因的果蝇卷翅的形成也有一定的影响,可以加大果蝇翅的卷曲程度.对SOD、CAT和GSH-PX活力检测发现,H_2O_2处理会使果蝇的抗氧化能力降低.实时荧光定量PCR检测发现,H_2O_2处理会导致果蝇基因表达量发生改变.黑腹果蝇卷翅形成是一个十分复杂的过程,H_2O_2可能作为某种信号分子或是间接影响某种因子参与黑腹果蝇的卷翅形成过程.该卷翅形成过程可能与Cy基因导致的果蝇卷翅过程是同一个信号途径,两者也可能是通过不同的模式进行调控的.     

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.     

Correlation of phenotypes of the apterous mutation in Drosophila melanogaster

The apterous (ap) mutant in Drosophila melanogaster exhibits phenotypes of wing deficiency, precocious adult death, and nonvitellogenic oocyte development. The latter phenotype previously has been shown to result from juvenile hormone (JH) deficiency in the adult stage. To explore the relationship between the hormone deficiency and the other phenotypes, the expression of each phenotype was measured in five alleles of ap (including a new, chemically-induced allele, ap^77f) as wing length, survival five days after eclosion, and initiation and progress of vitellogenic oocyte development. No correlation could be found between severity of wing phenotype and that of precocious adult death or nonvitellogenesis. However, the latter phenotypes were correlated in both ap homozygotes and allelic heterozygotes, since adults that survive have wild-type vitellogenesis, and those fated for precocious death fail to develop vitellogenic oocytes. These results indicate that no relationship exists between wing and JH deficiencies, but that precocious adult death is related to hormone deficiency — probably through pleiotropy, rather than through causality.     

黑腹果蝇杂交实验的教学改革

本文介绍关于黑腹果蝇杂交实验的一次教学改革尝试。讨论遗传学实验教学中,如何由常规的“验证性”教学改变为启发式的“发现式”教学,在本实验教学中,学生处于主导地位,自己选择实验组合,提出实验设计方案,独立完成实验内容;教师只是协助学生完成其实验内容。这种教学方法,充分发挥学生学习的主动性,培养学生独立思考和实际操作能力,激发学生的学习兴趣。 Abstract:The paper is concerned about a teaching and learning reform of hybridization experiment of Drosophila melanogaster.In the teaching of genetic experiment,we have adopted a new teaching and learning method which was a discovering way instead of tranditional method .In this way,students themselves selected the combination subject,put forward and carried out the whole experiment scheme.By the reform,we couldd find out that it was helpful not only to improve students' thinking and operating abilities but also to encourage their interests in genetics.     

DNA polymerase activity in developmental stages of Drosophila melanogaster

An assay procedure was developed that allowed the first reproducible measurement of DNA polymerase activity in all developmental stages of Drosophila melanogaster. Evidence is presented that the same enzymatic species is present in extracts of embryos, pupae, and adults of both sexes and that this activity has many properties similar to vertebrate α-polymerases. Polymerase activity per individual is low in embryos and rises steadily through larval instars, reaches a peak in early pupae, declines through the late pupal period, and remains low in newly eclosed adults of both sexes. A dramatic increase is observed in adult females as mature oocytes are formed. This pattern of enzyme activity is completely coincident with changes in DNA levels during development, and suggests that the Drosophila enzyme, like vertebrate α-polymerases, functions in cellular DNA replication. Two mutagen-sensitive mutants, deficient in both replication on undamaged templates and postreplication repair, were found to have normal levels of this α-polymerase activity. Our results suggest that a single enzymatic species of α-polymerase holoenzyme exists in Drosophila and is common to all developmental stages of this organism.