膜翅目昆虫补偿性性别决定机制

膜翅目昆虫单双倍体性别决定机制(雄性是单倍体、雌性是二倍体)在昆虫纲的进化中有非常重要的作用。通常膜翅目昆虫的性别由单一位点的等位基因决定,杂合体发育成雌性,半合体发育成雄性。在近亲繁殖的情况下,一定数目的雄性会出现纯合二倍体,由于遗传阻隔这种二倍体的雄性通常是不育的。csd基因的发现为膜翅目昆虫性别决定机制提供了分子生物学证据。文章探讨CSD的分子生物学基础,对膜翅目昆虫sl-CSD的分布进行综述并且探讨膜翅目昆虫降低二倍体雄性消耗的策略以及可能存在的进化机制,最后提出几点建议以便从遗传学、生态学以及进化生物学角度全面的了解sl-CSD。     

膜翅目寄生蜂的互补性别决定机制及其在生防上的意义(英文)

在膜翅目中 ,未受精卵形成单倍体的雄蜂 ,而在大多数情况下受精卵将产生双倍体的雌蜂。但是 ,因互补性别决定机制 (CSD)的作用 ,受精卵有时也会产生双倍体雄蜂。这种性别决定机制包括单位点的CSD和多位点的CSD。在单位点的CSD作用下 ,唯一的一个性位点上的多个等位基因决定后代个体的性别。性位点上杂合的个体将是雌性 ,半合或同型结合的个体将分别形成单倍体或双倍体的雄性。在多位点的CSD作用下 ,两个或两个以上的性位点控制后代的性别 ,每个性位点上包含两个或两个以上的等位基因。如果一个或一个以上的性位点是杂合的 ,形成的双倍体后代都是雌性的 ,但若是所有的性位点都为同型合子 ,则将产生双倍体的雄蜂。在膜翅目中 ,目前已知 4 3种具有双倍体雄蜂 ,其中 2 2种发现存在单位点的CSD ,但是多位点的CSD还有待于确认。双倍体的雄性个体或者不能存活 ,或者不育 ,这样的个体形成将对寄生蜂种群的增长带来一定的遗传负担。在生物防治上 ,保护寄生蜂种群的性等位基因的多样性及减少其遗传多异性的损失极其重要。如果利用具有单位点CSD的种类 ,采取一定的措施将可避免由于双倍体雄性的形成所带来的负面影响。     

昆虫性别决定研究进展

昆虫作为通过可变剪切调控性别决定的生物,拥有着保守性与多样性并存的性别决定机制。快速进化的上游性别决定初始信号使得几乎共享相同基因组的两性个体在形态、生理、行为等方面上有着巨大差异,而下游的双性基因doublesex在结构和功能上高度保守。本文综述了昆虫性别决定调控机制中初始信号的作用机理,概括了下游信号通路的响应机制,介绍了性别决定下游保守基因doublesex,以期为深入理解昆虫性别决定机制和农业害虫防治提供新思路。     

昆虫性别决定机制研究进展

阐述昆虫的性别决定机制是理解昆虫性别分化调控的理论基础,也为人类有效控制害虫开辟了新方向。昆虫性别决定机制存在复杂性和多样性,但主要是内因即性别决定基因级联互作调控的结果。本文对近年来基于性别决定基因级联互作的昆虫性别决定机制研究进行了综述,主要包括性别决定基因概况和重要性别决定相关基因的分子级联互作关系。目前发现昆虫重要性别决定相关基因主要集中在常染色体上,且部分基因之间存在紧密的级联互作,如Sxl,tra,dsx,csd和fem等。在这些基因中,tra/fem→dsx的调控模式在已报道的昆虫中存在共性,即tra和dsx相对较保守且tra通过性特异剪切来调控下游dsx的转录形式。目前大多数昆虫的性别决定机制还不清楚,但近年来模式昆虫性别决定机制取得了一定进展,对非模式昆虫的研究还处于起步阶段但却越来越受到重视。     

高等植物的性别与性别决定机制

生物在进化过程中出现了性别,有性繁殖是真核生物繁殖的主要形式,并导致了大多数真核生物两性异型的进化。本简要介绍了植物的性多态现象及雌雄异株植物的性染色体,主要介绍了雌雄异株植物的性别决定系统的三种基本类型,并与动物的性别决定系统作了比较。     

动物的性别决定

性别决定是指有性生物体未分化的生殖腺发育为卵巢或精巢的过程,其在生物界中广泛存在,是生物发育为雌、雄个体不可或缺的过程。对动物性别决定的定义及方式进行论述,主要阐述基因型性别决定、环境型性别决定和二者的相互作用,以及动物通过不同性别的转变来解决其生存过程中存在的各种问题。     

黄瓜性别决定相关基因和性别表达机制

介绍黄瓜的性别决定相关基因,黄瓜性别决定的假说和性别决定的分子机制的研究进展.     

性别决定基因

在个体发育过程中,动物的种类不同,性别决定的方式亦有差异。这取决于胚胎早期不同的性别初级信号对性别决定基因的启动和活化,活化的性别决定基因启动性别分化基因的表达,使个体的性别表现出来。本文略述与线虫、果蝇等的性别决定有关的基因。线虫(Caenorhabditis elegans)体长约1mm,雌雄同体,自体受精。有两条 X 染色体(XX);XO型线虫为雄性。线虫(C.elegans)性别决定的初级信号是 X 染色体与常染色体的比率(X∶     

COMPLEMENTARY SEX DETERMINATION IN HYMENOPTERAN PARASITOIDS AND ITS IMPLICATIONS FOR BIOLOGICAL CONTROL

In haplodiploid Hymenoptera, unfertilized eggs produce haploid males while fertilized eggs lead to diploid females under most circumstances. Diploid males can also be produced from fertilization under a system of sex determination known as complementary sex determination (CSD). Under single-locus CSD, sex is determined by multiple alleles at a single sex locus. Individuals heterozygous at the sex locus are female while hemizygous and homozygous individuals develop as haploid and diploid males, respectively. In multiple-locus CSD, two or more loci, each with two or more alleles, determine sex. Diploid individuals are female if one or more sex loci are het-erozygous, while a diploid is male only if homozygous at all sex loci. Diploid males are known to occur in 43 hym-enopteran species and single-locus CSD has been demonstrated in 22 of these species. Diploid males are either developmentally inviable or sterile, so their production constitutes a genetic load. Because diploid male production is more likely under inbreeding, CSD is a form of inbreeding depression. It is crucial to preserve the diversity of sex alleles and reduce the loss of genetic variation in biological control. In the parasitoid species with single-locus CSD, certain precautionary procedures can prevent negative effects of single-locus CSD on biological control.     

Effects of ploidy and sex-locus genotype on gene expression patterns in the fire ant Solenopsis invicta

Males in many animal species differ greatly from females in morphology, physiology and behaviour. Ants, bees and wasps have a haplodiploid mechanism of sex determination whereby unfertilized eggs become males while fertilized eggs become females. However, many species also have a low frequency of diploid males, which are thought to develop from diploid eggs when individuals are homozygous at one or more sex determination loci. Diploid males are morphologically similar to haploids, though often larger and typically sterile. To determine how ploidy level and sex-locus genotype affect gene expression during development, we compared expression patterns between diploid males, haploid males and females (queens) at three developmental timepoints in Solenopsis invicta. In pupae, gene expression profiles of diploid males were very different from those of haploid males but nearly identical to those of queens. An unexpected shift in expression patterns emerged soon after adult eclosion, with diploid male patterns diverging from those of queens to resemble those of haploid males, a pattern retained in older adults. The finding that ploidy level effects on early gene expression override sex effects (including genes implicated in sperm production and pheromone production/perception) may explain diploid male sterility and lack of worker discrimination against them during development.     

对蜜蜂性别决定和蜂王级型确立理论的新诠释

从全新视角概貌性解读蜜蜂Apis诸多生殖机制,依据的就是蜂王或产卵工蜂的卵子发生、性别决定假说、性位点研究以及蜂王级型确立机制。这种不同于单倍-二倍性性别决定机制的新诠释,适用于明确性别决定机制、简化定向育种方法、减少比较性实验的难度和时间、实施亲子鉴定和抽象并量化种群的概念。     

Inbreeding in a natural population of the gregarious parasitoid wasp Cotesia glomerata

Inbreeding occurs in numerous animal and plant species. In haplodiploid hymenopterans with the widespread single locus complementary sex determination, the frequency of diploid males, which are produced at the expense of females, is increased under inbreeding. Diploid males in species of bees, ants and wasps are typically either unviable or effectively sterile and thus impose a severe genetic load on populations. However, a recent study indicated that diploid males can be reproductive in the gregarious parasitoid wasp Cotesia glomerata, effectively reducing the diploid male load. To understand the role of inbreeding as a potential selective pressure towards the evolution of diploid male fertility, we genotyped specimens collected in the field at four locations using microsatellite markers to estimate the ratio of sibling matings under natural conditions. Results show that more than half of all matings involved siblings. We argue that the frequent occurrence of inbreeding has driven the evolution of diploid male fertility.     

Microsatellite DNA analysis reveals low diploid male production in a communal bee with inbreeding

The mechanism of sex determination assumed widespread in parthenogenetically arrhen-otokous Hymenoptera is that of single locus complementary sex determination (CSD). Functionally sterile diploid males are produced under CSD and generate a genetic load, the cost of which increases with inbreeding. We quantify diploid male production (DMP, proportion of diploid individuals that are male) using a morphological criterion (adult fresh weight) and genetical (microsatellite DNA) markers in a communal, sexually size-dimorphic bee, Andrma scotica , which inbreeds. Male genotypes suggested a DMP of 0.003. The inbreeding coefficient, f , was significandy positive (+ 0.165), equivalent to 44% of matings being among full sibs (predicted DMP of 0.11). We hypothesize three non-mutually exclusive explanations to account for the large difference between the low observed (in males) and high expected (derived fromy f for females) DMP: (i) multilocus CSD, (ii) 'sex allele signalling' tied to mate selection, and (iii) sperm selection within mated females. The costs of inbreeding through DMP are apparendy low in A. scotica .     

Complementary sex determination in the genus Diadegma (Hymenoptera: Ichneumonidae)

In the evolution of sexual reproduction we would expect to see a close association between mating systems and sex determination mechanisms. Such associations are especially evident in the insect order Hymenoptera which shows great diversity with respect to both of these characteristics. The ancestral sex determination mechanism in this order is thought to be single‐locus complementary sex determination (sl‐CSD), which is inbreeding sensitive, and where inbreeding results in the production of sterile diploid males rather than daughters. Presently, however, there is insufficient data to give strong support to the hypothesis that sl‐CSD is truly the ancestral condition in the Hymenoptera, principally because of the difficulty of reliably determining the degree of male ploidy. Here we show that six ichneumonid parasitoids from the polyphyletic genus Diadegma are subject to sl‐CSD, using neuronal cell DNA flow cytometry to distinguish ploidy levels. The presence of sl‐CSD in these six species, together with earlier evidence from the authors for D. chrysostictos, provides considerable support for the notion that sl‐CSD was ancestral in the Aculeata/Ichneumonoidea clade, which contains all eusocial Hymenoptera. Moreover, because flow cytometry discriminates reliably between haploid and diploid males, and is independent of the maternal sex allocation or the need for genetic markers, it has considerable potential for the determination of ploidy more generally.     

Occurrence of vitellogenin in drone honeybees (Apis mellifica)

Summary

The occurrence of vitellogenin in adult haploid drones of the honeybee, Apis mellifica, was determined by sensitive immunotechniques, i.e. two-dimensional Immunoelectrophoresis and SDS-PAGE immunoblotting using a monospecific anti-vitellogenin-serum. In drones vitellogenin is one of the minor fractions of the hemolymph proteins. Genetic and regulatory aspects of vitellogenin synthesis in male bees are discussed.