社会性昆虫级型和行为分化机制研究进展

社会性的出现是生物演化过程中的重要革新, 理解社会性的演化和调控机制具有重要的理论和实际意义。社会性昆虫的个体间有着明显的级型分化和劳动分工, 这有利于它们适应复杂的环境变化。理解社会性昆虫如何产生不同的形态、行为和生活史特性, 一直是进化和发育生物学的重要目标。随着测序技术的不断更新及生物信息学的快速发展, 已经有众多关于社会性昆虫级型和行为分化机制的研究报道。本文通过整理社会性昆虫研究的已有成果, 从环境因素、生理调控和分子机制等方面对社会性昆虫级型和行为分化机制相关研究进展进行了综述, 并对未来的研究方向做出了展望。根据现有证据, 社会性昆虫所生活的生物环境(食物营养、信息素、表皮碳氢化合物)和非生物环境(温度、气候等)均能直接或间接影响社会性昆虫级型和行为的分化; 保幼激素、蜕皮激素、类胰岛素及生物胺等内分泌激素和神经激素对社会性昆虫的级型和行为分化也有重要的调控作用; 此外, 遗传因素、新基因等DNA序列或基因组结构上的变化以及表观遗传修饰、基因的差异表达等基因调控机制均能不同程度地影响社会性昆虫的行为分化。本文建议加强昆虫纲其他社会性类群如半翅目蚜虫和缨翅目蓟马等的社会性行为及其演化机制的研究, 以加深对社会性昆虫起源及其行为演化的理解和认识。     

本期重点推介

<正>miRNA是一种长度为22 nt左右的内源性非编码RNA,可通过介导靶基因mRNA的降解或翻译抑制,参与大量基因调控网络,在包括细胞生长、增殖和分化的个体代谢和发育进程中起重要作用。为了明确昆虫精巢干细胞自我更新相关基因3'UTR上的保守miRNA靶位点,为深入研究昆虫精子发生进程中的miRNA-基因调控关系提供参考,南京农业大学植物保护学院马行洲和李飞以19个昆虫精巢干细胞自     

从形态学不同到基因水平差异: 家蚕与果蝇早期胚胎发育比较

昆虫的分化多样性一直是研究的一个热点, 对家蚕胚胎发育调控机制的研究将有助于加深人们对其他昆虫早期胚胎发育机制的了解。文章综述了鳞翅目昆虫家蚕和双翅目昆虫果蝇的早期胚胎发育在形态学及基因水平的研究结果。通过比较, 发现二者的早期胚胎发育存在较大差异。这一结果不但可以为家蚕胚胎发育调控机制的分子水平研究提供重要参考, 也可为昆虫分化多样性的分子机制研究提供线索。     

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。     

蜜蜂蜂王与工蜂级型分化研究进展

蜜蜂ApismekiferaL .是典型的社会性昆虫 ,蜂王和工蜂都是由受精卵发育而来的二倍体成蜂 ,但是在形态、生理、行为等方面有明显的差异 ,属于不同的级型。蜂王和工蜂的级型分化的关键时期发生在幼虫的 4龄末至 5龄止。分化是由分化基因调控的 ,幼虫期食物的质和量是分化的外部决定因子。JH对两级型中卵巢的分化有非常重要的调控作用。蜜蜂脑或其它组织中可能有分泌调控CA的咽侧体调节激素 ,它们通过对CA中JH的合成和分泌的调控而参与了分化的调控。章鱼胺等生物胺也参与了分化调控过程。     

蚂蚁亲系识别及研究方法进展

1前言亲系识别（Kinrecognition）是指社会性昆虫具有识别亲属与非亲属的能力,它被认为是昆虫社会性起源和演化的必要条件。此外,亲系识别在昆虫个体间的通讯、协作和繁衍等社会生活中具有重要作用。蚂蚁是社会性昆虫,许多种类表现出社群封闭性,即社群内相互合作和利它,而社群间表现出相互排斥,甚至强烈的进攻性。这一现象表明蚂蚁具有识别亲系的能力。揭示亲系识别的化学本质和遗传根源,不仅有助于对昆虫超社会性的起源和演化的研究,而且对行为学的其它相关学科（如行为生态学、行为遗传学、行为生理学）,进化生物学的研究以及人…     

蜜蜂级型分化机理

蜜蜂Apis spp.能有效地为多种植物及农作物授粉, 具有重要的经济和生态价值; 蜜蜂作为高度真社会性昆虫, 已成为社会生物学研究的模式生物。社会性昆虫的生殖劳动分工具有重要的进化意义, 而级型分化是形成生殖劳动分工的基础。近年来, 关于蜜蜂级型分化的研究已取得诸多重要成果, 其机理也得到了较为深入的阐释。营养差异引发蜜蜂幼虫的级型分化。蜂王浆中的主要蛋白组分之一--Royalactin是诱导蜂王发育的关键营养因子, 而脂肪体细胞的表皮生长因子受体介导了Royalactin的这种蜂王诱导作用。DNA甲基化是重要的表观遗传机制之一, 且与个体发育和疾病发生紧密相关, 近来的研究表明DNA甲基化在蜜蜂级型分化过程中发挥重要的调控作用。此外, 越来越多的研究进一步深化了人们对内分泌系统调节级型分化作用的认识。本文从关键营养因子调控、 表观遗传调控和内分泌调节3方面综述蜜蜂级型分化的机理, 并对未来的研究提出可能的方向。     

社会性昆虫的组织及通讯行为

社会性昆虫在自然界有很重要的生物学意义,社会性昆虫具有3个主要特征,真社会性昆虫包括全部蚂蚁、白蚁及部分胡蜂、蜜蜂。它们具有明显的等级分化和个体分工。通过报警、集聚、化学招引、摇摆舞等方式,社会性昆虫在其内部做了很好的通讯交流从而使其社会组织得到了很好的发展。     

昆虫卵黄原蛋白功能多效性：以蜜蜂为例

卵黄原蛋白是昆虫卵黄发生的关键物质。随着RNA干扰技术在功能基因研究中的应用和发展,昆虫卵黄原蛋白特别是蜜蜂卵黄原蛋白被发现具有气候适应、激活卵巢、生殖竞争、劳动力分化、行为构建、延长寿命、转化食物等多种功能,因此又被称为多效性蛋白。许多针对蜜蜂卵黄原蛋白功能和调控机制的假说也相继提出,如“交互抑制假说”、“循环反馈机制”、“卵黄原蛋白转化蛋白胨机制”,表明蜜蜂卵黄原蛋白已经由雌虫繁殖过程的一个下游因子上升为高等社会性昆虫主要生命周期的调控子,不仅极大地促进了昆虫社会生物学的研究,对其他具有复杂繁殖行为的昆虫的研究也具有重要的参考意义。针对近年来这一领域相继取得的重大突破,本文以蜜蜂为例介绍了昆虫卵黄原蛋白功能多效性的研究进展,包括卵黄原蛋白的理化性质与分子进化,发生与调控,功能多效性及其研究方法等     

熊蜂级型分化研究进展

熊蜂是众多野生植物及农作物的有效授粉昆虫,具有重要的经济和生态价值。熊蜂复杂的生长发育过程及社会性使其成为社会生物学研究的最佳模式生物之一。社会性昆虫的生殖劳动分工具有重要的进化意义,而级型分化是形成生殖劳动分工的基础。蜜蜂级型分化的研究已取得诸多重要成果,其机理也得到了较为深入的阐释,而熊蜂的社会性研究尚未形成系统,与蜜蜂研究相差甚远。近来的研究表明,饲喂频率或者饲喂总量的差异能够引起熊蜂级型分化的发生。保幼激素和蜕皮激素与熊蜂幼虫的发育紧密联系,在熊蜂级型分化的过程中发挥重要作用。一些参与蜜蜂级型分化的基因,在熊蜂级型间也存在差异表达。此外,群体间的相互作用以及蜂王和工蜂间的竞争也是促进熊蜂级型分化发生的重要因素。本文从营养、激素调控、群体发展及相互作用等方面综述熊蜂级型分化机制,并对未来的研究提出可能方向。     

Genetic components to caste allocation in a multiple-queen ant species

Reproductive division of labor and the coexistence of distinct castes are hallmarks of insect societies. In social insect species with multiple queens per colony, the fitness of nestmate queens directly depends on the process of caste allocation (i.e., the relative investment in queen, sterile worker and male production). The aim of this study is to investigate the genetic components to the process of caste allocation in a multiple-queen ant species. We conducted controlled crosses in the Argentine ant Linepithema humile and established single-queen colonies to identify maternal and paternal family effects on the relative production of new queens, workers, and males. There were significant effects of parental genetic backgrounds on various aspects of caste allocation: the paternal lineage affected the proportion of queens and workers produced whereas the proportions of queens and males, and females and males were influenced by the interaction between parental lineages. In addition to revealing nonadditive genetic effects on female caste determination in a multiple-queen ant species, this study reveals strong genetic compatibility effects between parental genomes on caste allocation components.     

Genomic imprinting and evolution of insect societies

Reproductive division of labor is a hallmark of social insect societies where individuals follow different developmental pathways resulting in distinct morphological castes. There has been a long controversy over the factors determining caste fate of individuals in social insects. Increasing evidence in the last two decades for heritable influences on division of labor put an end to the assumption that social insect broods are fully totipotent and environmental factors alone determine castes. Nevertheless, the genes that underlie hereditary effects on division of labor have not been identified in any social insects. Studies investigating the hereditary effects on caste determination might have overlooked non-genetic inheritance, while transmission to offspring of factors other than DNA sequences including epigenetic states can also affect offspring phenotype. Genomic imprinting is one of the most informative paradigms for understanding the consequences of interactions between the genome and the epigenome. Recent studies of genomic imprinting show that genes can be differentially marked in egg and sperm and inheritance of these epigenetic marks cause genes to be expressed in a parental-origin-specific manner in the offspring. By reviewing both the eusocial Hymenoptera and termites, I highlight the current theoretical and empirical evidence for genomic imprinting in eusocial insects and discuss how genomic imprinting acts in caste determination and social behavior and challenges for future studies. I also introduce the new idea that genomic imprinting plays an essential role in the origin of eusociality.     

Evidence for genetically influenced caste determination in phylogenetically diverse species of the termite genus Reticulitermes

A number of social insect species have recently been shown to have genetically influenced caste determination (GCD), challenging the conventional view that caste determination should be strictly environmental. To date, GCD has been found in phylogenetically isolated species; examples of GCD being present in multiple species of a genus are lacking. Through crossing experiments of neotenic (juvenile) reproductives, we have recently provided the first evidence for a royal versus worker GCD in the termite Reticulitermes speratus. To elucidate whether this system is more widespread, we performed crossing experiments using three additional Reticulitermes species. Offspring caste and sex ratios were found to be highly similar to those found previously in R. speratus, raising the possibility that GCD was present in an ancestral lineage of Reticulitermes, and subsequently maintained throughout several episodes of speciation.     

Loss of phenotypic plasticity generates genotype-caste association in harvester ants

Caste differentiation and reproductive division of labor are the hallmarks of insect societies. In ants and other social Hymenoptera, development of female larvae into queens or workers generally results from environmentally induced differences in gene expression. However, several cases in which certain gene combinations may determine reproductive status have been described in bees and ants. We investigated experimentally whether genotype directly influences caste determination in two populations of Pogonomyrmex harvester ants in which genotype-caste associations have been observed. Each population contains two genetic lineages. Queens are polyandrous and mate with males of both lineages , but in mature colonies, over 95% of daughter queens have a pure-lineage genome, whereas all workers are of F1 interlineage ancestry. We found that this pattern is maintained throughout the colony life cycle, even when only a single caste is being produced. Through controlled crosses, we demonstrate that pure-lineage eggs fail to develop into workers even when interlineage brood are not present. Thus, environmental caste determination in these individuals appears to have been lost in favor of a hardwired genetic mechanism. Our results reveal that genetic control of reproductive fate can persist without loss of the eusocial caste structure.     

A genetic component in the determination of worker polymorphism in the Florida harvester ant Pogonomyrmex badius

Summary. The interplay of genetic and environmental factors in the determination of social insect castes has long intrigued biologists. Though an overwhelming majority of studies establish that factors such as nutrition, pheromones and temperature determine the developmental fate of worker larvae, genetic components have recently been shown to play a role in the determination of morphological worker castes in leaf-cutting ants. Here we demonstrate that the determination of worker castes in the strongly polyandrous Florida harvester ant, Pogonomyrmex badius, has a genetic component. The overall distribution of caste members among patrilines in our study colonies is significantly different from the intracolonial caste ratio. Though this effect was not apparent in all colonies, our results suggest that workers of different patrilines in P. badius differ significantly in their propensities to develop into a certain worker caste. This genetic basis of worker polymorphism may go unnoticed in many social hymenopterans because of their low intracolonial genetic diversity due to monogamous colony structure. The worker polymorphism of P. badius is a taxonomic isolate and presumably a young trait in the genus. Therefore, a common genetic component of the determination of morphological and behavioral worker castes in social insects might be farranging taxonomically and may even be based on a genetic machinery inherent to all hymenopterans, but dormant in most.Received 3 May 2004; revised 27 October 2004; accepted 8 November 2004.     

Gene expression and the evolution of insect polyphenisms

Polyphenic differences between individuals arise not through differences at the genome level but as a result of specific cues received during development. Polyphenisms often involve entire suites of characters, as shown dramatically by the polyphenic castes found in many social insect colonies. An understanding of the genetic architecture behind polyphenisms provides a novel means of studying the interplay between genomes, gene expression and phenotypes. Here we discuss polyphenisms and molecular genetic tools now available to unravel their developmental bases in insects. We focus on several recent studies that have tracked gene-expression patterns during social insect caste determination. BioEssays 23:62-68, 2001. Published 2001 John Wiley & Sons, Inc.     

The social regulation of physical caste: the superorganism revived

Among the ants, the population of worker phenotypes made by a colony is closely regulated. For the first time, a model of the regulation of a particular size class, that of major workers, is developed within a new theory of the superorganismic activity of social insect colonies. A remarkable linkage is found to exist between caste homeostasis in a model polymorphic society and three well-known but previously unrelated social insect colony properties: the form of the caste distribution, the short-term nature of a colony's “memory”, and the existence of co-operative interactions among nestmates. The linkage consists of mass social processes and takes the form of a colony-level, negative feedback circuit controlling the production of the major workers. The implications of this case study for rigorous, substantive theories of social insect mass phenomena are discussed.     

Worker caste determination in the army ant Eciton burchellii

Elaborate division of labour has contributed significantly to the ecological success of social insects. Division of labour is achieved either by behavioural task specialization or by morphological specialization of colony members. In physical caste systems, the diet and rearing environment of developing larvae is known to determine the phenotype of adult individuals, but recent studies have shown that genetic components also contribute to the determination of worker caste. One of the most extreme cases of worker caste differentiation occurs in the army ant genus Eciton, where queens mate with many males and colonies are therefore composed of numerous full-sister subfamilies. This high intracolonial genetic diversity, in combination with the extreme caste polymorphism, provides an excellent test system for studying the extent to which caste determination is genetically controlled. Here we show that genetic effects contribute significantly to worker caste fate in Eciton burchellii. We conclude that the combination of polyandry and genetic variation for caste determination may have facilitated the evolution of worker caste diversity in some lineages of social insects.     

Hold the germ cells, I'm on duty

Germ cell segregation and gamete production are developmental problems that all sexually reproducing species must solve in order to survive. Many people are familiar with the complex social structures of some insect species, where specialised castes of adult insects perform specific tasks, one of which is usually to guard the sexually reproductive queen. The parasitic wasp Copidosoma floridanum adds another level of complexity to the caste system: a fertilised egg produces both sterile, short-lived "soldier" larvae and "reproductive" larvae that complete metamorphosis to produce sexually reproductive adults. How two morphologically and functionally distinct larval castes are produced by genetically identical groups of cells developing under the same environmental conditions is a baffling problem. A recent paper suggests that differential germ cell segregation during embryogenesis may be an event both necessary and sufficient for caste determination.(1)