Extra-pair copulation and sperm competition in the zebra finch

Most birds are monogamous, but recent studies have shown that extra-pair copulations (EPCs) occur frequently despite a range of paternity guards, including mate-guarding and frequent copulation. Although EPCs are known to result in extra-pair paternity, there are no previous quantitative estimates of the success of EPCs in fertilizing eggs. We present here estimates of the likelihood of success of extra-pair copulations in a monogamous passerine, the zebra finch Poephila guttata. We show that (1) EPCs occurring under semi-natural conditions in captivity result in extra-pair paternity, (2) sperm from the last male to mate has precedence over previous matings: a single EPC occurring last is disproportionately successful in fertilizing eggs, but EPCs followed by further pair copulations have a low probability of success. These results have important implications for sexual selection theory.     

A new statistical method for mapping QTLs underlying endosperm traits

Genetic expression for an endosperm trait in seeds of cereal crops may be controlled simultaneously by the triploid endosperm genotypes and the diploid maternal genotypes. However, current statistical methods for mapping quantitative trait loci （QTLs） underlying endosperm traits have not been effective in dealing with the putative maternal genetic effects. Combining the quantitative genetic model for diploid maternal traits with triploid endosperm traits, here we propose a new statistical method for mapping QTLs controlling endosperm traits with maternal genetic effects. This method applies the data set of both DNA molecular marker genotypes of each plant in segregation population and the quantitative observations of single endosperms in each plant to map QTL. The maximum likelihood method implemented via the expectation-maximization algorithm was used to the estimate parameters of a putative QTL. Since this method involves the maternal effect that may contribute to endosperm traits, it might be more congruent with the genetics of endosperm traits and more helpful to increasing the precision of QTL mapping. The simulation results show the proposed method provides accurate estimates of the QTL effects and locations with high statistical power.     

籼粳交稻米品质性状的遗传相关分析

用种子性状遗传模型对籼粳交稻米８个主要品质性状的遗传相关进行了研究。结果表明,在籼粳杂种中,稻米品质性状之间的遗传相关主要涉及到种子直接遗传效应和母体遗传效应。其中,５个理化品质性状之间以直接效应相关为主,其次为母体效应相关;５个理化品质性状与３个外观品质性状之间只有直接加性、母体加性和母体显性相关;３个外观品质性状之间的遗传相关主要归因于母体效应。尤其是母体加性效应。在所有的性状对中,仅胶稠度和     

珍珠鸟和家鸡甲状旁腺激素3型受体(PTH3R)的结构与表达图谱分析

甲状旁腺激素(PTH)与动物钙稳态调控和骨代谢平衡相关,其生理作用是通过甲状旁腺激素受体(PTHR)介导。甲状旁腺激素受体家族包括三个不同的亚型,其中甲状旁腺激素3型受体(PTH3R)在非哺乳类脊椎动物生长发育过程中起着重要作用,然而PTH3R在鸟类中的研究则相对较少。 本研究采用RT-PCR方法,首先克隆了珍珠鸟和家鸡的PTH3R基因全长cDNA序列。结果显示,家鸡PTH3R (cPTH3R) cDNA全长1632 bp,编码543个氨基酸,珍珠鸟PTH3R(zPTH3R-w) cDNA序列全长1563 bp,编码520个氨基酸,其蛋白均含有信号肽序列、七次跨膜区等特征性结构。此外,在珍珠鸟中还发现一个新剪接变体zPTH3R-v1,其cDNA序列全长1468 bp,编码488个氨基酸,其缺失了第3外显子进而导致第1跨膜结构域缺失。利用生物信息学方法,我们还对珍珠鸟和家鸡PTH3R蛋白序列进行三维建模。 采用RT-PCR方法,本研究也对珍珠鸟PTH3R基因进行组织表达分析。结果显示,zPTH3R及其剪切变体zPTH3R-v1在珍珠鸟脑及外周组织中广泛表达。珍珠鸟和家鸡PTH3R基因的成功克隆与结构解析,将为下一步开展PTH3R在鸟类中的功能研究奠定重要基础。     

Genetic basis of fitness differences in natural populations

Genomics profoundly influences current biology. One of many exciting consequences of this revolution is the potential for identifying and studying the genetic basis of those traits affecting fitness that are key to natural selection. Recent studies using a multitude of genomic approaches have established such genotype-phenotype relationships in natural populations, giving new insight into the genetic architecture of quantitative variation. In parallel, an emerging understanding of the quantitative genetics of fitness variation in the wild means that we are poised to see a synthesis of ecological and molecular approaches in evolutionary biology.     

The Drosophila melanogaster Genetic Reference Panel

A major challenge of biology is understanding the relationship between molecular genetic variation and variation in quantitative traits, including fitness. This relationship determines our ability to predict phenotypes from genotypes and to understand how evolutionary forces shape variation within and between species. Previous efforts to dissect the genotype-phenotype map were based on incomplete genotypic information. Here, we describe the Drosophila melanogaster Genetic Reference Panel (DGRP), a community resource for analysis of population genomics and quantitative traits. The DGRP consists of fully sequenced inbred lines derived from a natural population. Population genomic analyses reveal reduced polymorphism in centromeric autosomal regions and the X chromosome, evidence for positive and negative selection, and rapid evolution of the X chromosome. Many variants in novel genes, most at low frequency, are associated with quantitative traits and explain a large fraction of the phenotypic variance. The DGRP facilitates genotype-phenotype mapping using the power of Drosophila genetics.     

Genetic mechanisms of floral trait correlations in a natural population

Genetic correlations among traits are important in evolution, as they can constrain evolutionary change or reflect past selection for combinations of traits. Constraints and integration depend on whether the correlations are caused by pleiotropy or linkage disequilibrium, but these genetic mechanisms underlying correlations remain largely unknown in natural populations. Quantitative trait locus (QTL) mapping studies do not adequately address the mechanisms of within-population genetic correlations because they rely on crosses between distinct species, inbred lines or selected lines (see ref. 5), and they cannot distinguish moderate linkage disequilibrium from pleiotropy because they commonly rely on only one or two episodes of recombination. Here I report that after nine generations of enforced random mating (nine episodes of recombination), correlations between six floral traits in wild radish plants are unchanged, showing that pleiotropy generates the correlations. There is no evidence for linkage disequilibrium despite previous correlational selection acting on one functionally integrated pair of traits. This study provides direct evidence of the genetic mechanisms underlying correlations between quantitative traits in a natural population and suggests that there may be constraints on the independent evolution of pairs of highly correlated traits.     

成年雄性斑胸草雀脑多巴胺D1受体的分布

多巴胺是脑内关键的神经递质,它通过与多巴胺受体的作用及其下游的一系列反应来影响基因表达、神经调节和行为活动.在成年鸣禽中,中脑多巴胺能神经元投射到X区、HVC和RA等鸣唱相关核团,释放多巴胺的量受一定社会情境的影响,从而表现出directed song和undirected song等不同鸣唱行为.获得斑胸草雀脑中多巴胺受体的表达情况,为与社会情境有关的鸣唱行为及其他和多巴胺相关的行为活动的神经机制探究提供了基础,并可促进行为学、电生理等方面的研究.我们发现D1受体在斑胸草雀脑中的分布与其mRNA的分布基本一致:在脑的绝大部分区域都有分布;主要鸣唱核团HVC和RA有表达,与其周围区域差异不明显;LMAN中表达量较少;DLM中的表达量较高,并与其周围区域差异明显.但是纹状体内的表达与其周围区域的差异性没有mRNA明显;GCT中的表达量较多,与周围区域差异明显.     

The role of nonlinear dynamics of the syrinx in the vocalizations of a songbird

Birdsong is characterized by the modulation of sound properties over a wide image of timescales. Understanding the mechanisms by which the brain organizes this complex temporal behaviour is a central motivation in the study of the song control and learning system. Here we present evidence that, in addition to central neural control, a further level of temporal organization is provided by nonlinear oscillatory dynamics that are intrinsic to the avian vocal organ. A detailed temporal and spectral examination of song of the zebra finch (Taeniopygia guttata) reveals a class of rapid song modulations that are consistent with transitions in the dynamical state of the syrinx. Furthermore, in vitro experiments show that the syrinx can produce a sequence of oscillatory states that are both spectrally and temporally complex in response to the slow variation of respiratory or syringeal parameters. As a consequence, simple variations in a small number of neural signals can result in a complex acoustic sequence.     

表观遗传学研究进展

 概述了表观遗传调节模式、表观遗传调节的效应、植物表观遗传学的研究进展等。在每种细胞中,都会发生一部分特异基因激活、另一部分基因抑制的现象,形成多种基因表达模式。表观遗传指DNA序列不发生变化,而基因表达发生可遗传改变的现象。表观遗传学改变包括DNA甲基化、组蛋白修饰、非编码RNA作用等,产生基因组印记、母性影响、基因沉默、核仁显性、休眠转座子激活等效应。表观遗传变异是环境因素和细胞内遗传物质间交互作用的结果,其效应通过调节基因表达,控制生物学表型来实现。正是因为表观修饰对于维持生物体内环境和各器官系统功能的重要性,表观遗传的异常会引发疾病,这也成为药物和治疗方案设计的着眼点。     

Epistasis and balanced polymorphism influencing complex trait variation

Complex traits such as human disease, growth rate, or crop yield are polygenic, or determined by the contributions from numerous genes in a quantitative manner. Although progress has been made in identifying major quantitative trait loci (QTL), experimental constraints have limited our knowledge of small-effect QTL, which may be responsible for a large proportion of trait variation. Here, we identified and dissected a one-centimorgan chromosome interval in Arabidopsis thaliana without regard to its effect on growth rate, and examined the signature of historical sequence polymorphism among Arabidopsis accessions. We found that the interval contained two growth rate QTL within 210 kilobases. Both QTL showed epistasis; that is, their phenotypic effects depended on the genetic background. This amount of complexity in such a small area suggests a highly polygenic architecture of quantitative variation, much more than previously documented. One QTL was limited to a single gene. The gene in question displayed a nucleotide signature indicative of balancing selection, and its phenotypic effects are reversed depending on genetic background. If this region typifies many complex trait loci, then non-neutral epistatic polymorphism may be an important contributor to genetic variation in complex traits.     

Genetic variation increases during biological invasion by a Cuban lizard

A genetic paradox exists in invasion biology: how do introduced populations, whose genetic variation has probably been depleted by population bottlenecks, persist and adapt to new conditions? Lessons from conservation genetics show that reduced genetic variation due to genetic drift and founder effects limits the ability of a population to adapt, and small population size increases the risk of extinction. Nonetheless, many introduced species experiencing these same conditions during initial introductions persist, expand their ranges, evolve rapidly and become invasive. To address this issue, we studied the brown anole, a worldwide invasive lizard. Genetic analyses indicate that at least eight introductions have occurred in Florida from across this lizard's native range, blending genetic variation from different geographic source populations and producing populations that contain substantially more, not less, genetic variation than native populations. Moreover, recently introduced brown anole populations around the world originate from Florida, and some have maintained these elevated levels of genetic variation. Here we show that one key to invasion success may be the occurrence of multiple introductions that transform among-population variation in native ranges to within-population variation in introduced areas. Furthermore, these genetically variable populations may be particularly potent sources for introductions elsewhere. The growing problem of invasive species introductions brings considerable economic and biological costs. If these costs are to be mitigated, a greater understanding of the causes, progression and consequences of biological invasions is needed.     

Polyandrous females avoid costs of inbreeding.

Why do females typically mate with more than one male? Female mating patterns have broad implications for sexual selection, speciation and conflicts of interest between the sexes, and yet they are poorly understood. Matings inevitably have costs, and for females, the benefits of taking more than one mate are rarely obvious. One possible explanation is that females gain benefits because they can avoid using sperm from genetically incompatible males, or invest less in the offspring of such males. It has been shown that mating with more than one male can increase offspring viability, but we present the first clear demonstration that this occurs because females with several mates avoid the negative effects of genetic incompatibility. We show that in crickets, the eggs of females that mate only with siblings have decreased hatching success. However, if females mate with both a sibling and a non-sibling they avoid altogether the low egg viability associated with sibling matings. If similar effects occur in other species, inbreeding avoidance may be important in understanding the prevalence of multiple mating.     

云南松的种群遗传与进化

本文从种群遗传学的角度研究了云南松（pinus yunnanensis)的遗传体制，种群内的多态现象，种群的遗传结构，演化潜力，生态小种和地理小种以及共交种等问题，得出的若干结论如下：（1）种内存在巨大的遗传变异，如在自然 群中表明的，几乎所有可见的形态性状都具有多态现象，这种巨大的遗传变异是自然选择进化的一个必要条件。（2）自然种群中，大多数个体的基因型很多座位都是杂合的，它们常表现出杂种优势，并且也可能表明增强了生理上发育上的体内平衡。（3）由于种群大，而且又分割成许多相对独立的亚群，各种进化要素都有能同时起作用，并已分化出生态种和地理小种，（4）云南松具有拟态种子，其起源和适应意义作了初步讨论。     

Hsp90 as a capacitor of phenotypic variation

Heat-shock protein 90 (Hsp90) chaperones the maturation of many regulatory proteins and, in the fruitfly Drosophila melanogaster, buffers genetic variation in morphogenetic pathways. Levels and patterns of genetic variation differ greatly between obligatorily outbreeding species such as fruitflies and self-fertilizing species such as the plant Arabidopsis thaliana. Also, plant development is more plastic, being coupled to environmental cues. Here we report that, in Arabidopsis accessions and recombinant inbred lines, reducing Hsp90 function produces an array of morphological phenotypes, which are dependent on underlying genetic variation. The strength and breadth of Hsp90's effects on the buffering and release of genetic variation suggests it may have an impact on evolutionary processes. We also show that Hsp90 influences morphogenetic responses to environmental cues and buffers normal development from destabilizing effects of stochastic processes. Manipulating Hsp90's buffering capacity offers a tool for harnessing cryptic genetic variation and for elucidating the interplay between genotypes, environments and stochastic events in the determination of phenotype.     

Post-mating sexual selection increases lifetime fitness of polyandrous females in the wild

Females often mate with several males before producing offspring. Field studies of vertebrates suggest, and laboratory experiments on invertebrates confirm, that even when males provide no material benefits, polyandry can enhance offspring survival. This enhancement is widely attributed to genetic benefits that arise whenever paternity is biased towards males that sire more viable offspring. Field studies suggest that post-mating sexual selection biases fertilization towards genetically more compatible males and one controlled experiment has shown that, when females mate with close kin, polyandry reduces the relative number of inbred offspring. Another potential genetic benefit of polyandry is that it increases offspring survival because males with more competitive ejaculates sire more viable offspring. Surprisingly, however, there is no unequivocal evidence for this process. Here, by experimentally assigning mates to females, we show that polyandry greatly increases offspring survival in the Australian marsupial Antechinus stuartii. DNA profiling shows that males that gain high paternity under sperm competition sire offspring that are more viable. This beneficial effect occurs in both the laboratory and the wild. Crucially, there are no confounding non-genetic maternal effects that could arise if polyandry increases female investment in a particular reproductive event because A. stuartii is effectively semelparous. Our results therefore show that polyandry improves female lifetime fitness in nature. The threefold increase in offspring survival is not negated by a decline in maternal lifespan and is too large to be offset by an equivalent decline in the reproductive performance of surviving offspring.     

Control of the sperm-oocyte switch in Caenorhabditis elegans hermaphrodites by the fem-3 3' untranslated region.

In the Caenorhabditis elegans hermaphrodite germ line, sperm and then oocytes are made from a common pool of germ-cell precursors. The decision to differentiate as a sperm or an oocyte is regulated by the sex-determining gene, fem-3. Expression of fem-3 in the hermaphrodite germ line directs spermatogenesis and must be negatively regulated to allow the switch to oogenesis. In adult hermaphrodites (which are producing oocytes), most fem-3 RNA is found in the germ line, consistent with both the requirement for fem-3 in hermaphrodite spermatogenesis and the maternal effects of fem-3 on embryonic sex determination. Whereas loss-of-function mutants in fem-3 produce only oocytes, hermaphrodites carrying any of nine fem-3 gain-of-function (gf) mutations make none; instead sperm are produced continuously and in vast excess over wild-type amounts. Genetic analyses suggest that fem-3(gf) mutations have escaped a negative control required for the switch to oogenesis. Here we report that all nine fem-3(gf) mutants carry sequence alterations in the fem-3 3' untranslated region (3' UTR). There is no increase in the steady-state level of fem-3(gf) RNA over wild-type, but there is an increase in the polyadenylation of fem-3(gf) RNA that is coincident with the unregulated fem-3 activity. Results of a titration experiment support the hypothesis that a regulatory factor may bind the fem-3 3' UTR. We speculate that fem-3 RNA is regulated through its 3' UTR by binding a factor that inhibits translation, and discuss the idea that this control may be part of a more general regulation of maternal RNAs.     

Molecular and phenotypic variation in the achaete-scute region of Drosophila melanogaster

Variation in quantitative characters underlies much adaptive evolution and provides the basis for selective improvement of domestic species, yet the genetic nature of quantitative variation is poorly understood. Many loci affecting quantitative traits have been identified by the segregation of mutant alleles with major qualitative effects. These alleles may represent an extreme of a continuum of allelic effects, and most quantitative variation could result from the segregation of alleles with subtle effects at loci identified by alleles with major effects. The achaete-scute complex in Drosophila melanogaster plays a central part in bristle development and has been characterized at the molecular level. The hypothesis that naturally occurring quantitative variation in bristle number could be associated with wild-type alleles of achaete-scute was tested by correlating phenotypic variation in bristle number with molecular variation in restriction maps in this region among chromosomes extracted from natural populations. DNA insertion variation in the achaete-scute region was found to be strongly associated with variation in bristle number.     

动物指(趾)长比研究进展

指长比(FLRs)是指人类或动物的指(趾)长度的比值.目前人们认为人类的食指与无名指的长度比值(2D∶4D)可以作为是否受到产前性激素的影响(PAE)一个生物学标记.近几十年来人类FLRs研究在国内外得到快速发展.已经涉及基因调控、利手现象、心脏病、乳腺癌、性格特征、不对称、运动能力和孤独症等方面.进一步研究发现在其他一些哺乳动物中FLRs也存在一定性差,例如,小鼠、狒狒、大猩猩,黑猩猩、斑马雀和蜥蜴等.本文对动物的FLRs研究进展做一综述.     

Genetic linkage of ecological specialization and reproductive isolation in pea aphids

The evolution of ecological specialization generates biological diversity and may lead to speciation. Genetic architecture can either speed or retard this process. If resource use and mate choice have a common genetic basis through pleiotropy or close linkage, the resulting genetic correlations can promote the joint evolution of specialization and reproductive isolation, facilitating speciation. Here we present a model of the role of genetic correlations in specialization and speciation, and test it by analysing the genetic architecture of key traits in two highly specialized host races of the pea aphid (Acyrthosiphon pisum pisum; Hemiptera : Aphididae). We found several complexes of pleiotropic or closely linked quantitative trait loci (QTL) that affect key traits in ways that would promote speciation: QTL with antagonistic effects on performance on the two hosts are linked to QTL that produce asortative mating (through habitat choice). This type of genetic architecture may be common in taxa that have speciated under divergent natural selection.