共生微生物对昆虫化学感受的影响北大核心

共生微生物通过影响昆虫信息化合物的合成或感受来调控宿主的化学通讯,进而影响昆虫的交流、防御、捕食和扩散行为。这种调控作用有助于共生微生物的扩散,但对宿主可能是有利的,也可能是有害的,并为共生体系的协同进化提供动力。本文围绕近年来共生微生物对昆虫化学感受的影响及其机制展开综述,并分析其进化意义,旨在为昆虫化学生态学理论提供补充,并为开发新的害虫防治策略提供思路。     

昆虫体外共生菌研究进展

昆虫体外共生菌是指能在体外与宿主发生互利共生关系的微生物。体外共生菌虽然不如肠道微生物那样普遍存在于昆虫中,但也在宿主生长发育过程中扮演着重要的角色。昆虫体外共生菌一般寄生于昆虫体表或体内特异器官(如储菌器),在特定时期转移到植物组织中。体外共生菌产生的挥发物能作为宿主定位寄主植物的信号物质,能为宿主提供生长发育所需的营养物质,还参与了宿主体外免疫。对昆虫体外共生菌的研究,不仅能进一步揭示昆虫与微生物之间的互作关系,丰富昆虫共生菌的研究,还能从共生菌的角度探索害虫引诱剂和昆虫免疫豁免机制。本文对昆虫体外共生菌寄生方式、传播途径、对宿主的影响等研究成果进行了综述,旨在为害虫综合防控提供新思路。     

泛素-蛋白酶体系统在昆虫先天免疫中的调控作用

完善的先天免疫系统使得昆虫成为分布最广、适应性最强、物种多样性最丰富的动物类群。在长期的进化过程中,昆虫建立了一套安全有效的先天免疫系统,一方面在面对外界微生物攻击的时候及时有效的发生免疫应答反应;另一方面通过免疫抑制来调控适度免疫应答,避免对自身发动攻击和控制环境共生菌刺激引起的免疫应答信号通路的持续激活。泛素-蛋白酶体系统在昆虫先天免疫中具有重要的调控作用,在Toll和IMD信号通路中,通过对免疫应答通路中信号分子的泛素化修饰加工,促进或抑制抗菌肽的表达,从而使免疫反应达到一个平衡。本文通过对泛素-蛋白酶体系统在Toll和IMD信号通路中的免疫应答和免疫抑制方面的研究进行综述,阐明了该系统在昆虫先天免疫中的调控作用,将有助于开展农业害虫与其天敌之间相互关系的深入研究,揭示其免疫调控机理,为开发生物农药,进行生物防控提供理论依据。     

昆虫共生菌的垂直传播

共生菌普遍存在于昆虫体内,它们能够为宿主昆虫提供生长发育所必需的氨基酸、固醇类等营养物质,还能提高昆虫适应高温、寄生虫、病毒等不利环境因素的能力,昆虫则为共生菌提供稳定的生存环境和营养物质,昆虫与共生菌相互依存。多数情况下,共生菌通过垂直传播在宿主代次间进行传播,即共生菌由母代传递给子代。结合最近几年相关研究,本文综述了不同昆虫共生菌的垂直传播模式。除极少数肠道共生菌通过污染卵壳被宿主幼虫取食得以垂直传播外,垂直传播的共生菌多为经卵传播。根据侵染时期的不同,共生菌经卵传播模式多数可分为以下4种：侵染宿主昆虫幼虫中的生殖干细胞、侵染宿主昆虫年轻雌成虫中的生殖干细胞、侵染宿主昆虫雌成虫中的成熟卵母细胞以及侵染宿主昆虫囊胚期胚胎。其中,有些共生菌是以共生菌菌胞整体侵染的方式进入到宿主卵巢。另外,少数肠道共生菌也通过卵巢进行垂直传播,此类共生菌先侵染卵巢侧输卵管并在侧输卵管聚集,待卵排放至侧输卵管时再进入到卵中。在文中,我们也探讨了昆虫共生菌垂直传播过程中的细胞机制和免疫机制,包括共生菌避开宿主免疫反应、共生菌通过内吞作用进入卵巢以及不同共生菌间的协同作用等。     

昆虫内共生菌及其功能研究进展

昆虫内共生菌与宿主之间的互作关系已逐渐成为昆虫学的研究热点之一。昆虫内共生菌具有协助宿主营养代谢、 逃避天敌攻击和增强抗药性等功能： 通过协助宿主营养代谢, 提供食物中缺乏的营养物质来弥补食物中营养物质的不足; 分泌抗菌肽、 毒素等物质以增强对外源寄生物等的防御能力, 抑制对宿主的不利影响; 同时, 也可以增强宿主抗逆性, 调控植物生理反应, 抑制植物对宿主的不利影响; 利用对抗逆性基因精确的表达调控来增强宿主抗药性等。因此, 内共生菌介导的宿主生物学性状的改变, 扩大了宿主昆虫的生态位, 成为昆虫生长发育过程中的重要调控因子。目前, 昆虫内共生菌的功能往往是通过研究宿主感染共生菌前后性状的变化而证实。近几年, 转录组学、 蛋白质组学、 基因组学等技术的进步, 促进了内共生菌与宿主昆虫共生机制研究的发展。通过研究内共生菌及其功能基因在昆虫种群动态中的作用, 特别是内共生菌感染对宿主生殖、 存活、 适应环境能力的影响, 将有利于揭示内共生菌与宿主的共生机制, 并最终为开发新的防控技术提供理论依据。本文针对昆虫内共生菌的功能进行了综述, 并对日后的研究方向进行了展望, 提供了研究昆虫内共生菌与宿主互作关系的方法及建议。     

布鲁氏菌逃避宿主免疫机制的研究进展

布鲁氏菌病是由布鲁氏菌引起的一种人畜共患性传染病,可以对畜牧业生产和人类健康造成严重的危害。布鲁氏菌是兼性胞内寄生菌,在长期与宿主免疫系统的相互作用中,进化出了多种逃避宿主免疫应答的机制。该文主要概述了布鲁氏菌胞内循环过程和逃避宿主先天性免疫应答和适应性免疫应答的机制,以及通过激活非典型自噬途径、抑制细胞凋亡、调控细胞焦亡等方式建立慢性感染的策略,以期为进一步深入研究布鲁氏菌病以及病原与宿主的相互作用提供参考。     

昆虫次生内共生菌Rickettsia研究进展

Rickettsia隶属于变形菌纲Proteobacteria的α亚群立克次体科Rickettsiaceae革兰氏阴性菌,是形态多样的次生真核细胞内共生菌。Rickettsia的功能是多样的,在一些宿主中为营养共生菌,在另一些宿主中为生殖调控因子,或以昆虫为载体的植物病原菌,此外,Rickettsia还能增强宿主抗药性,提高宿主抵御天敌、高温或者其它致死因素的能力。本综述主要从Rickettsia的起源、分类、在昆虫体内的分布、传播方式、与昆虫生殖调控的关系以及基因组进化等方面,简述Rickettsia的研究进展,重点提出了Rickettsia研究中一些尚未解决的问题,期望通过这些研究进一步明确Rickettsia与昆虫之间的互作关系。     

共生菌与昆虫抗药性

越来越多的研究表明,共生菌与昆虫的抗药性存在一定的联系.在不同的虫菌共生体系中,共生菌和昆虫抗药性联系的表现型存在较大的差异.昆虫对抗药性的生理补偿效应会影响共生菌群落组成.反之,共生菌通过提高宿主的适合度,利用自身的解毒作用或通过免疫系统间接调控宿主的解毒能力来影响宿主昆虫的抗药性.多组学和分子生物学技术的发展有助于对共生菌和昆虫抗药性的联系进行更深入的研究.     

昆虫共生菌对宿主功能研究的方法体系

共生菌可参与昆虫的生理生化过程,影响昆虫的营养、生长发育、解毒作用、天敌防御和免疫能力等。在共生菌对宿主功能的研究中,核心问题是如何从组成复杂的共生菌组中筛选出具有特定功能的共生菌。共生菌对宿主功能的研究模式通常包括:通过共生菌多样性分析,提出差异共生菌对宿主功能的假设;分析并验证特定共生菌在宿主体内的功能。本文围绕共生菌对宿主功能的研究模式,系统地总结和比较昆虫共生菌功能研究的方法和技术,构建昆虫对宿主功能研究的方法体系,以期推进共生菌-宿主联系的研究。     

共生菌与昆虫抗药性

越来越多的研究表明,共生菌与昆虫的抗药性存在一定的联系.在不同的虫菌共生体系中,共生菌和昆虫抗药性联系的表现型存在较大的差异.昆虫对抗药性的生理补偿效应会影响共生菌群落组成.反之,共生菌通过提高宿主的适合度,利用自身的解毒作用或通过免疫系统间接调控宿主的解毒能力来影响宿主昆虫的抗药性.多组学和分子生物学技术的发展有助于...     

Surface polysaccharides enable bacteria to evade plant immunity

Plants have an immune system to perceive pathogenic or potentially beneficial bacteria. Aspects of perception, signal transduction and the responses that the plant produces resemble features of innate immunity observed in animals. Plant reactions are various and include the production of antimicrobial compounds. Bacteria that are successful in establishing pathogenic or symbiotic interactions have developed multiple ways to protect themselves. We review the general importance of bacterial surface polysaccharides in the evasion of plant immune responses and elaborate on their role in protecting symbiotic bacteria against toxic reactive oxygen species during invasion of the host plant.     

Immunity and symbiosis

The invertebrate immune system, which has become a major research focus, shares basic features of innate immunity with vertebrates and men. A special feature apparently found only in invertebrates is their close association with vertically heritable symbiotic microorganisms. The validity of the simple view of symbiosis as a mutually beneficial interaction between two uneven partners mainly improving the nutritional state of the two companions has been challenged, however, as symbiotic interactions might involve more partners, and symbiotic functions of the microorganisms are much more diverse than previously assumed. Likewise, microorganisms considered to be mostly harmful to their hosts have been shown to enhance host fitness under some circumstances. The role of a symbiont itself might change between environments or life stages of the host and symbionts might have features previously thought to be specific for pathogens. Understanding symbiotic interactions requires the comprehension of the cross-talk between the symbiotic companions, and the dissection of how long-lasting infections are established without eliminating the symbiont by host immune responses. Fascinating new findings in this field revealed that symbiosis might contribute to defence against pathogens or natural enemies. New symbiont-based approaches to defeat agricultural pests or pathogen transmission by arthropod vectors are becoming conceivable.     

Masters of conquest and pillage: Xenorhabdus nematophila global regulators control transitions from virulence to nutrient acquisition

Invertebrate animal models are experimentally tractable and have immunity and disease symptoms that mirror those of vertebrates. Therefore they are of particular utility in understanding fundamental aspects of pathogenesis. Indeed, artificial models using human pathogens and invertebrate hosts have revealed conserved and novel molecular mechanisms of bacterial infection and host immune responses. Additional insights may be gained from investigating interactions between invertebrates and pathogens they encounter in their natural environments. For example, enteric bacteria in the genera Photorhabdus and Xenorhabdus are pathogens of insects that also mutualistically associate with nematodes in the genera Heterorhabditis and Steinernema respectively. These bacteria serve as models to understand naturally occurring symbiotic associations that result in disease in or benefit for animals. Xenorhabdus nematophila is the best-studied species of its genus with regard to the molecular mechanisms of its symbiotic associations. In this review, we summarize recent advances in understanding X. nematophila –host interactions. We emphasize regulatory cascades involved in coordinating transitions between various stages of the X. nematophila life cycle: infection, reproduction and transmission.     

Intracellular innate resistance to bacterial pathogens

Mammalian innate immunity stimulates antigen-specific immune responses and acts to control infection prior to the onset of adaptive immunity. Some bacterial pathogens replicate within the host cell and are therefore sheltered from some protective aspects of innate immunity such as complement. Here we focus on mechanisms of innate intracellular resistance encountered by bacterial pathogens and how some bacteria can evade destruction by the innate immune system. Major strategies of intracellular antibacterial defence include pathogen compartmentalization and iron limitation. Compartmentalization of pathogens within the host endocytic pathway is critical for generating high local concentrations of antimicrobial molecules, such as reactive oxygen species, and regulating concentrations of divalent cations that are essential for microbial growth. Cytosolic sensing, autophagy, sequestration of essential nutrients and membrane attack by antimicrobial peptides are also discussed.     

Yersinia effectors target mammalian signalling pathways

Animals have an immune system to fight off challenges from both viruses and bacteria. The first line of defence is innate immunity, which is composed of cells that engulf pathogens as well as cells that release potent signalling molecules to activate an inflammatory response and the adaptive immune system. Pathogenic bacteria have evolved a set of weapons, or effectors, to ensure survival in the host. Yersinia spp. use a type III secretion system to translocate these effector proteins, called Yops, into the host. This report outlines how Yops thwart the signalling machinery of the host immune system.     

肠粘膜上皮细胞在天然免疫中的作用

粘膜免疫是机体防御系统的主要成分。致病性细菌侵入机体后,首先遭遇到天然免疫的抵抗,随后产生获得性免疫,两共同执行机体的防御功能,消灭入侵细菌。最近的研究表明上皮细胞对细菌感染有重要的免疫调节作用,在天然免疫与获得性免疫防御机制中起重要作用。本重点介绍肠上皮细胞在天然免疫中的作用。     

Condition-dependent alteration of cellular immunity by secondary symbionts in the pea aphid,Acyrthosiphon pisum

Endosymbionts can fundamentally alter host physiology. Whether such changes are beneficial or detrimental to one or both partners may depend on the dynamics of the symbiotic relationship. Here we investigate the relationship between facultative symbionts and host immune responses. The pea aphid, Acyrthosiphon pisum, maintains an obligate primary symbiont, but may also harbour one or more facultative, secondary symbionts. Given their more transient nature and relatively recent adoption of a symbiotic lifestyle compared to primary symbionts, secondary symbionts may present a challenge for the host immune system. We assessed the response of several key components of the cellular immune system (phenoloxidase activity, encapsulation, immune cell counts) in the presence of alternative secondary symbionts, investigating the role of host and secondary symbiont genotype in specific responses. There was no effect of secondary symbiont presence on the phenoloxidase response, but we found variation in the encapsulation response and in immune cell counts based largely on the secondary symbiont. Host genotype was less influential in determining immunity outcomes. Our results highlight the importance of secondary symbionts in shaping host immunity. Understanding the complex physiological responses that can be propagated by host-symbiont associations has important consequences for host ecology, including symbiont and pathogen transmission dynamics.     

Dissecting the immune response to the entomopathogen Photorhabdus

Bacterial pathogens either hide from or modulate the host's immune response to ensure their survival. Photorhabdus is a potent insect pathogenic bacterium that uses entomopathogenic nematodes as vectors in a system that represents a useful tool for probing the molecular basis of immunity. During the course of infection, Photorhabdus multiplies rapidly within the insect, producing a range of toxins that inhibit phagocytosis of the invading bacteria and eventually kill the insect host. Photorhabdus bacteria have recently been established as a tool for investigating immune recognition and defense mechanisms in model hosts such as Manduca and Drosophila. Such studies pave the way for investigations of gene interactions between pathogen virulence factors and host immune genes, which ultimately could lead to an understanding of how some Photorhabdus species have made the leap to becoming human pathogens.     

Modulation of host immunity by beneficial microbes

In nature, plants abundantly form beneficial associations with soilborne microbes that are important for plant survival and, as such, affect plant biodiversity and ecosystem functioning. Classical examples of symbiotic microbes are mycorrhizal fungi that aid in the uptake of water and minerals, and Rhizobium bacteria that fix atmospheric nitrogen for the plant. Several other types of beneficial soilborne microbes, such as plant-growth-promoting rhizobacteria and fungi with biological control activity, can stimulate plant growth by directly suppressing deleterious soilborne pathogens or by priming aboveground plant parts for enhanced defense against foliar pathogens or insect herbivores. The establishment of beneficial associations requires mutual recognition and substantial coordination of plant and microbial responses. A growing body of evidence suggests that beneficial microbes are initially recognized as potential invaders, after which an immune response is triggered, whereas, at later stages of the interaction, mutualists are able to short-circuit plant defense responses to enable successful colonization of host roots. Here, we review our current understanding of how symbiotic and nonsymbiotic beneficial soil microbes modulate the plant immune system and discuss the role of local and systemic defense responses in establishing the delicate balance between the two partners.