昆虫内共生菌研究概况*

内共生菌与昆虫形成互惠共生关系,在宿主昆虫的生长、生殖、传播植物病害以及探讨生命起源与进化等等方面都有很重要的意义。从昆虫内共生菌的特点、内共生菌在昆虫体内的分布、对昆虫的影响、获得少或缺内共生菌的方法及其研究内共生菌的潜在意义等方面进行了综述。     

植物介导的昆虫内共生菌水平传播及其对宿主生物学特性的影响

内共生菌(Endosymbionts)与其昆虫宿主的生物学特性联系非常密切。近年来,昆虫内共生菌水平传播的途径及机制已经成为昆虫学研究的热点之一。越来越多的研究表明,亲缘关系相距甚远的昆虫可以感染有相同或相似的内共生菌,说明昆虫内共生菌的水平传播在自然界中普遍存在。植物介导的昆虫内共生菌水平传播便是其中的一条途径,即同种或不同种类的昆虫可以通过取食,获得供体昆虫传入植物组织中的内共生菌,形成内共生菌从供体昆虫-寄主植物-受体昆虫传播的路径。本文主要以植物介导的昆虫内共生菌水平传播途径为对象,介绍了昆虫内共生菌的水平传播途径,以及内共生菌传入后对新宿主生物学、生态学特性的影响,以期为昆虫内共生菌水平领域的研究提供更多有价值的参考。     

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。     

刺吸式昆虫次生内共生菌的研究进展

蚜虫作为典型的刺吸式昆虫,需要以取食植物韧皮部汁液来补充营养,几乎所有蚜虫均带有一种能为其提供植物韧皮部缺失营养物质的初生共生菌Buchnera aphidicola。此外,蚜虫还可携带一种或多种次生内共生菌。在众多共生菌—寄主系统中,蚜虫与其所带内共生菌间的互作研究最为透彻。虽然次生内共生菌对寄主的存活和生殖影响并不显著,但其在寄主对环境耐受力、天敌防御能力等方面作用明显。本文在查阅大量蚜虫次生内共生菌相关文献的基础上,着重对蚜虫次生内共生菌的种类及传播规律、次生内共生菌对蚜虫表型的影响、蚜虫次生内共生菌基因组学等方面的研究现状进行综述,以求为刺吸式昆虫次生内共生菌的研究提供参考。     

鳞翅目昆虫内共生菌研究进展

内共生菌(endosymbionts)与其昆虫宿主的共生关系是普遍存在的，它们彼此相互依赖、相互影响、协同进化。近年来，关于昆虫内共生菌的研究多以半翅目(Hemiptera)和双翅目(Diptera)昆虫为主，但数量不断增加的研究表明鳞翅目(Lepidoptera)昆虫与其体内共生菌的互作模式和机制也正在受到越来越多的关注。鳞翅目昆虫种类多，分布广，主要作为植食者、传粉者在生态系统中发挥作用，而其绝大部分幼虫会对农林业生产造成巨大经济损失。鳞翅目昆虫体内共生菌群落多样性相对较低，主要以次生共生菌Wolbachia为主，少数也感染有Spiroplasma，Arsenophonus及Rickettsia。它们常呈严格的母系垂直传播，也会发生一定比例的水平传播，在宿主的生长发育、生殖调控、环境适应、遗传进化方面发挥重要作用。目前一般采用诊断性聚合酶链反应、高通量扩增子测序、宏基因组测序等方法检测内共生菌。但鳞翅目昆虫内共生菌研究领域存在一些难点，包括：大多数内共生菌无法离体培养；丰度较低的内共生菌的生物学功能难以确定。基于鳞翅目昆虫内共生菌的分布及该领域的难点，建议未来的研究重点应放在次生共生菌及其生物学功能上。     

昆虫内共生菌及其传病毒相关GroEL蛋白

昆虫传播的植物病毒种类多、危害大,其传病毒的能力与昆虫体内共生菌产生的GroEL蛋白关系密切,该蛋白是分子伴侣hsp60家族的成员,对病毒进入昆虫血体腔免遭破坏起着保护作用,也与昆虫传病毒的专一性有关。本对昆虫内共生菌及其产生的GroEL进行了综述,并分析了研究内共生菌及其产生的蛋白质的科学意义与发展趋势,为植物病毒病的防治研究提供了新的思路。     

三种抗生素去除大青叶蝉内共生菌的效果

内共生菌能够为寄主提供营养物质,同时在宿主昆虫的生长及生殖等方面具有特殊作用,大青叶蝉Cicadella viridis与其他昆虫一样具有内共生菌。本文设计了大青叶蝉内共生菌Sulcia muelleri和Sodalis sp.的特异性引物,检测其在大青叶蝉中的感染率;同时分别用利福平、盐酸土霉素和青霉素G钾盐3种抗生素处理大青叶蝉,用TaqMan探针法绝对定量PCR检测不同处理时间下大青叶蝉内共生菌的拷贝数。结果表明:大青叶蝉内共生菌Sulcia muelleri和Sodalis sp.的带菌率均为100%;利福平、盐酸土霉素和青霉素G钾盐均可使内共生菌的量减少,但不能完全消除。3种抗生素均能显著减少大青叶蝉雌虫和雄虫中内共生菌Sulcia muelleri 16S rRNA基因拷贝数。盐酸土霉素和利福平均能显著降低大青叶蝉若虫和雄虫中内共生菌Sodalis sp. 16S rRNA基因拷贝数,但对雌虫影响不显著。     

蚜虫初级内共生菌Buchnera aphidicola研究进展

动物和细菌的内共生关系一直是生物学关注的热点,相关研究不但对于了解动物宿主的生长、繁殖等有重要意义,也有助于探讨生命起源和进化等生命现象。蚜虫类昆虫体内存在一类专性的胞内共生菌Buchnera,它对于蚜虫营养代谢和正常发育至关重要,被称为蚜虫的初级内共生菌。由于两者间具有专性共生关系,使其成为内共生关系研究的理想模型。本文将从Buchnera的基本特征、Buchnera与蚜虫进化关系、Buchnera在共生关系中的作用及Buchnera基因组学等方面对Buchnera研究现状进行综述,并对未来的研究热点进行展望。     

昆虫专性内共生细菌及其基因组研究进展

昆虫专性内共生细菌是一类与宿主昆虫长期协同进化的共生微生物,在许多昆虫体内均有发现,主要存在于昆虫特化的器官(含菌体)内,以垂直传播的方式由母系遗传。专性内共生细菌与昆虫的生存、繁殖以及进化等方面息息相关,其主要功能是为宿主提供必需氨基酸等营养物质。因其长期生活在宿主细胞内处于封闭的高营养的环境中,其基因组的特征与普通细菌基因组有很大区别,包括基因组大小、GC含量、基因缺失等方面。通过对共生细菌基因水平上的深入研究,有助于理解专性内共生细菌在宿主昆虫协同进化过程中的作用。目前,昆虫内共生细菌基因的生物学功能、内共生细菌之间以及内共生细菌与宿主之间的互作机制还不是很清楚,有待进一步的研究和探索。     

共生菌Cardinium在宿主体内的分布、检测及其生殖调控作用

内共生菌是存在于宿主细胞内,与宿主存在互利共生关系的一类细菌。内共生菌在节肢动物的生长和繁殖过程中起着十分重要的作用, 包括向宿主提供食物中缺乏的营养物质、调控宿主生殖方式,增强宿主适应性等。Cardinium属于拟杆菌门Bacteroidetes,通过细胞质遗传,具有诱导宿主细胞质不亲和、产雌孤雌生殖、雌性化等生殖异常现象,并且还可影响宿主的适合度,以利于其本身在宿主不同种群和世代间的分布和传播。由于Cardinium是近几年人们新发现的一类新型内共生菌,目前对其在节肢动物宿主体内的分布、其生物学生态学功能等尚不完全明确。本文在综合国内外文献资料的基础上,从Cardinium在节肢动物体内的分布、其在昆虫种群的传播规律及其检测手段、其对节肢动物宿主的生殖调控作用等几个方面进行了综述,并对其应用前景进行了展望,以期引起更多的学者关注该胞内共生菌,推动人们对该内共生菌的研究及利用。     

枣园害虫、捕食性和中性昆虫群落结构及动态研究

对山西省太谷地区枣园的害虫、捕食性和中性昆虫群落结构及动态进行研究,结果表明,不同年份枣园的害虫、捕食性和中性昆虫种类与数量均有明显差异(P<0.05),且树上明显大于地面.不同年份捕食性和中性昆虫与害虫的物种数和个体数比例也不同,其物种数和个体数随季节的暖和冷而增加和减少.相同亚群落不同季节的垂直分层结构相似程度不同,不同亚群落在同一季节的垂直分层相似性也不同.总体上垂直分层明显.枣园害虫、捕食性和中性昆虫的多样性指数随季节变化而波动.捕食性和中性昆虫与害虫数量起伏跟随紧密,总体呈极显著相关(r=0.9833,P<0.05).层次间差异明显,以中层相关最显著(r=0.9887,P<0.01)     

Aggregation in the haematophagous bug Triatoma infestans: a novel assembling factor

Abstract. The response of Triatoma infestans (Klug) to odours left behind by walking insects was analysed. The insects aggregated on papers marked with putative chemical footprints in the absence of other assembling chemical signals. Contact of the receptor insect with the treated surface was necessary to elicit the response because the signal was not able to attract insects, only to arrest them on marked surfaces. These requirements contrast with other chemical aggregation signals of triatomines that attract the insect and involve olfactory responses. By washing the cuticle of the insects with hexane and impregnating papers with the extract, a response was evoked in test insects similar to that elicited by papers on which insects had walked. The biological role of this novel aggregation factor is discussed in relation to other assembling signals of different origin.     

Effects of insects on primary production in temperate herbaceous communities: a meta-analysis

Abstract.  1. The effects of insects on primary production in temperate herbaceous communities were investigated in a meta-analysis. The following hypotheses were tested: (1) the effect of insects on primary production depends on community type, (2) the effect of insects on primary production varies as a function of productivity, (3) insects have a greater effect on primary production in communities with low species diversity, and (4) insects have a larger effect on primary production during outbreaks.
2. Data were collected from 24 studies in which insecticides were used to suppress insects in self-sown or pastoral communities. Effect sizes were calculated from sprayed and control plot standing crop or yield, expressed as the log response ratio, ln (sprayed plot phytomass/control plot phytomass).
3. There was a significant increase in primary production as a result of insect suppression. Forb-dominated communities showed a more variable response than graminoid communities. During outbreaks, insects had a greater negative impact on primary production. Effect size was unaffected by productivity or plant species richness.
4. Although insects lower primary production in a diversity of temperate herbaceous communities, the basic measures by which such communities are often described have little effect on the proportional impact that insects have on primary production. While outbreaks are significant predictors of higher negative impact on primary production, causes of outbreaks are not always related to traits of the plant community.     

大叶醉鱼草访花昆虫行为与活动规律

于2009年4～9月对云南农业大学苗圃内栽植的大叶醉鱼草访花昆虫进行观察。结果表明,大叶醉鱼草的访花昆虫有63种,隶属双翅目、半翅目、膜翅目、鳞翅目、鞘翅目、革翅目和螳螂目;食蚜蝇科为大叶醉鱼草种群的主要传粉昆虫;不同月份访花昆虫的种类不同;天气变化会影响访花昆虫的种类和数量;同一天内不同时间,访花昆虫的访花频率有差异,一般每天12:00～16:00的访花频率最高。     

Suppression of the prophenoloxidase system in Rhodnius prolixus orally infected with Trypanosoma rangeli

Investigations were carried out to compare aspects of the prophenoloxidase (proPO)-activating pathway in Rhodnius prolixus hemolymph in response to oral infection and inoculation of the insects with two developmental forms of Trypanosoma rangeli epimastigotes strain H14. In vivo experiments demonstrated that in control insects fed on uninfected blood, inoculation challenge with short epimastigotes resulted in high phenoloxidase (PO) activity. In contrast, previous feeding on blood containing either short or long epimastigotes was able to suppress the proPO activation induced by thoracic inoculation of the short forms. In vitro assays in the presence of short epimastigotes demonstrated that control hemolymph or hemolymph provided by insects previously fed on blood containing epimastigotes incubated with fat body homogenates from control insects significantly increased the PO activity. However, fat body homogenates from insects previously fed on blood containing epimastigotes, incubated with hemolymph taken from insects fed on control blood or blood infected with epimastigotes, drastically reduced the proPO activation. The proteolytic activity in the fat body homogenates of control insects was significantly higher than in those obtained from fat body extracts of insects previously fed on blood containing epimastigotes. These findings indicate that the reduction of the proteolytic activities in the fat body from insects fed on infected blood no longer allows a significant response of the proPO system against parasite challenge. It also provides a better understanding of T. rangeli infection in the vector and offer novel insights into basic immune processes in their invertebrate hosts.     

枣麦间作枣园主要蚧虫复合种群结构及生态位

为了有效地控制枣树蚧害,2002年在太谷地区对枣麦间作枣园的康氏粉蚧(Pseudococcus comstock Kuwane)、日本蜡蚧(Ceroplastes japonicus Green)和梨园蚧(Quadraspidiotus perniciosus Comstock)的复合种群结构及其生态位进行了系统研究.结果表明,在枣树发育早期,3种蚧虫分布范围主要在下、中部的东、南方位,康氏粉蚧的时空二维生态位的宽度较大,是该时期的优势种.到中期3种蚧虫复合种群的分布聚集在树冠上部的西、北方位,时 空二维生态位的宽度以日本蜡蚧较大,种间相似程度和竞争不明显.后期3种蚧虫的复合种群结构在各部位的各个方位的分布无明显差异,但梨园蚧的虫口密度较大,日本蜡蚧在生态位上占据较大的空间.与枣树发育的中期相比,3种蚧虫复合种群结构的相似性与种间竞争系数的平均值要小.蚧害预防应早期控制康氏粉蚧,中期调治3种蚧虫的危害,后期应采取措施压低越冬虫源.     

昆虫DNA甲基化的特点和功能

DNA甲基化为表观遗传修饰的一种主要形式, 对基因表达的调控具有重要作用。近年来随着有关昆虫DNA甲基化的研究和报道增多, 发现昆虫DNA甲基化除了与高等哺乳动物有一定的相似性之外, 还具有独特的特点和功能。本文就昆虫DNA甲基化的主要特点和功能进行了综述, 以期为进一步研究昆虫DNA甲基化提供借鉴和参考。不同昆虫所具有的DNA甲基转移酶种类和性质差异较大, 且昆虫DNA甲基化具有甲基化水平较低、主要发生在基因区等特点, 其功能主要涉及到调节胚胎发育、参与基因组印迹、调控级型和翅型分化、影响性别决定、介入抗药性形成等。     

The insect faunas of pear and apple orchards and the effect of windbreaks on their distribution

Two coir netting windbreaks, each 7 m tall and 46 m long, were erected in a pear and an apple orchard, to try to increase the number of insect pollinators present at blossom time. The flying insects were sampled with suction traps and insects visiting trees were sampled by examining marked clusters of blossom. The mean aerial density was calculated for each of the forty-two taxa, mainly families, identified from the aerial population. There were about 50% more insects flying in the pear than in the apple orchard. The distribution of flying insects was greatly affected by the windbreaks, and the sheltered zone contained three times as many of most species, and more than three times as many Chironomidae, Psychodidae and Bibionidae as elsewhere. Small flies were the most abundant insects in the air, in both orchards. In the pear orchard large insects comprised only about 7 % of the total aerial population, of which honeybees constituted 0–7% and wild bees 0–3%. By contrast, large insects accounted for a greater proportion of the population on blossom. The reasons for this are discussed. On apple blossom Syrphidae and honeybees were the insects most often seen, and on pear blossom Bibionidae and Mycetophilidae.     

Response of nuclear polyhedrosis virus-resistant Spodoptera frugiperda larvae to other pathogens and to chemical insecticides

Selection in the laboratory for Spodoptera frugiperda (Sf) resistant to nuclear polyhedrosis virus (NPV) affected the susceptibility of the insect to certain other mortality agents, including a chemical insecticide. Median lethal concentrations (LC50S) and associated statistics were compared for several mortality agents between colonies of NPV-resistant and -susceptible (control) insects. Compared to the susceptible insects, the NPV-resistant insects were cross-resistant to the S. frugiperda granulosis virus and to the Autographa californica NPV based on nonoverlap of 95% fiducial limits of the LC50S. The NPV-resistant insects were significantly more susceptible to methyl parathion than the control insects. The two colonies of S. frugiperda did not differ significantly in their response to Bacillus thuringiensis, Vairimorpha necatrix, or carbaryl. The cross-resistance experiments were based on per os exposure of the insects to the pathogens and insecticides; the susceptibility of the resistant and control insects did not differ significantly when the Sf NPV was injected into the hemocoel or when methyl parathion was applied topically.     

The relative importance of lethal and non-lethal effects of fish on insect colonisation of ponds

1. We hypothesised that adult insects actively monitor potential habitats for the presence of fish by means of chemical cues and avoid sites that pose significant risks. This was examined by quantifying colonisation of insects in outdoor pools with no fish (controls), fish (direct predation effect) or caged fish (chemical predator cues).
2. A significant direct effect of predation was found, but no indirect effect (avoidance of chemical cue pools), on the total biomass of colonising insects. However, predatory insects avoided fish-cue pools, thus releasing non-predatory insects from predation. This resulted in significantly greater biomass of non-predatory insects in fish-cue pools than control pools.
3. Fish reduced the number of species of colonising insects in pools through predation. This negative influence of fish implies that caution is necessary when stocking wetlands and ponds with fish if the goal is to maximise biodiversity.
4. Our data suggest that although predatory aquatic insects may use chemical signals to assess the quality of potential habitats with respect to predation risk, direct predation is the main method by which fish affect insect assemblages in ponds. Because fish and invertebrate predators may both have strong effects on prey mortality, behavioural adjustment by insects to the actual predator regime within a habitat should be more important than avoiding colonisation of habitats with fish.