Wolbachia and virus protection in insects

Wolbachia pipientis bacteria are common endosymbionts of insects that are best known for their ability to increase their prevalence in populations by manipulating host reproductive systems. However, there are examples of Wolbachia that exist in nature that seem to induce no reproductive parasitism trait and yet are able to invade populations. We demonstrate a fitness benefit for Wolbachia-infected insects that may explain this paradox. Drosophila melanogaster flies infected with Wolbachia are less susceptible to mortality induced by a range of RNA viruses. The antiviral protection associated with Wolbachia infection might be exploited in future strategies to reduce transmission of pathogens by insects.     

The Anopheles genome and comparative insect genomics

The Anopheles gambiae genome sequence, coupled with the Drosophila melanogaster genome sequence, provides a better understanding of the insects, a group that contains our friends, foes, and competitors.     

小菜蛾肌球蛋白重链部分cDNA序列克隆、表达概况及分析

肌肉肌球蛋白重链在生物运动过程中具有至关重要的作用,但在昆虫中此类基因极少被报道。首次克隆和分析小菜蛾肌球蛋白重链部分cDNA序列,GenBank登录号为FJ462712,其长408个碱基,推测编码135个氨基酸。同源分析表明:此多肽序列与凤蝶、家蚕、果蝇的同源性分别为95%,93%,82%。半定量RT-PCR研究表明:小菜蛾MHC基因在不同的生长发育阶段的表达皆不相同,在老熟幼虫和成虫中的表达量显著高于低龄幼虫和蛹。为进一步鉴定小菜蛾肌球蛋白重链的生理特征提供基因序列信息。     

A functional dosage compensation complex required for male killing in Drosophila

Bacteria that selectively kill males ("male-killers") were first characterized more than 50 years ago in Drosophila and have proved to be common in insects. However, the mechanism by which sex specificity of virulence is achieved has remained unknown. We tested the ability of Spiroplasma poulsonii to kill Drosophila melanogaster males carrying mutations in genes that encode the dosage compensation complex. The bacterium failed to kill males lacking any of the five protein components of the complex.     

Substitution of the thioredoxin system for glutathione reductase in Drosophila melanogaster

The disulfide reducing enzymes glutathione reductase and thioredoxin reductase are highly conserved among bacteria, fungi, worms, and mammals. These proteins maintain intracellular redox homeostasis to protect the organism from oxidative damage. Here we demonstrate the absence of glutathione reductase in Drosophila melanogaster, identify a new type of thioredoxin reductase, and provide evidence that a thioredoxin system supports GSSG reduction. Our data suggest that antioxidant defense in Drosophila, and probably in related insects, differs fundamentally from that in other organisms.     

RH 5849, a nonsteroidal ecdysone agonist: effects on a Drosophila cell line

The steroid molting hormone 20-hydroxyecdysone is the physiological inducer of molting and metamorphosis in insects. In ecdysone-sensitive Drosophila Kc cells, the insecticide RH 5849 (1,2-dibenzoyl-1-tert-butylhydrazine) mimics the action of 20-hydroxyecdysone by causing the formation of processes, an inhibition of cell proliferation, and induction of acetylcholinesterase. RH 5849 also competes with [3H]ponasterone A for high-affinity ecdysone receptor sites from Kc cell extracts. Resistant cell populations selected by growth in the continued presence of either RH 5849 or 20-hydroxyecdysone are insensitive to both compounds and exhibit a decreased titer of measurable ecdysone receptors. Although it is less potent than 20-hydroxyecdysone in both whole-cell and cell-free receptor assays, RH 5849 is the first nonsteroidal ecdysone agonist.     

Insect odorant receptors are molecular targets of the insect repellent DEET

DEET (N,N-diethyl-meta-toluamide) is the world's most widely used topical insect repellent, with broad effectiveness against most insects. Its mechanism of action and molecular target remain unknown. Here, we show that DEET blocks electrophysiological responses of olfactory sensory neurons to attractive odors in Anopheles gambiae and Drosophila melanogaster. DEET inhibits behavioral attraction to food odors in Drosophila, and this inhibition requires the highly conserved olfactory co-receptor OR83b. DEET inhibits odor-evoked currents mediated by the insect odorant receptor complex, comprising a ligand-binding subunit and OR83b. We conclude that DEET masks host odor by inhibiting subsets of heteromeric insect odorant receptors that require the OR83b co-receptor. The identification of candidate molecular targets for the action of DEET may aid in the design of safer and more effective insect repellents.     

2个新的鳞翅目OR83b类化感蛋白基因的克隆和序列分析

【目的】分离和克隆昆虫触角中一类非常保守的嗅觉受体蛋白基因全序列。【方法】采用简并引物反转录多聚酶链式反应(RT-PCR)和cDNA末端快速扩增(RACE)技术克隆基因,用生物信息学方法对获得的cDNA全序列及推导的氨基酸序列进行分析。【结果】从甜菜夜蛾(Spodoptera exigua Hübner)和斜纹夜蛾[Spodoptera litura(Fabricius)]雄蛾触角中扩增得到2个分别为1906bp和2483bp的OR83类化感蛋白基因的cDNA,开放阅读框(ORF)编码473个氨基酸,命名为SexiOR2和SlitOR2。通过在GenBank中进行序列的同源性比较,发现这2个鳞翅目化感蛋白新序列与已知蛾类昆虫的OR83b类化感蛋白氨基酸序列具较高的同源性。【结论】明确了所获得的2个鳞翅目蛋白新序列属于OR83b类化感蛋白。     

筛选敏感昆虫检测拟除虫菊酯类农药残留*

 选取拟除虫菊酯类农药中有代表性农药,对长期室内饲养的家蝇、果蝇、马铃薯块茎蛾、米象及黄粉虫等进行毒力测定,筛选出相对敏感昆虫用于检测拟除虫菊酯类农药残留,并通过色谱法对其检测结果进行评价。结果显示:家蝇对拟除虫菊酯类最敏感(溴氰菊酯LC₅₀=0.08487μg/mL,氰戊菊酯LC₅₀=5.5602μg/mL),其检测灵敏度可与色谱相媲美。     

Genome sequence of Aedes aegypti, a major arbovirus vector

We present a draft sequence of the genome of Aedes aegypti, the primary vector for yellow fever and dengue fever, which at approximately 1376 million base pairs is about 5 times the size of the genome of the malaria vector Anopheles gambiae. Nearly 50% of the Ae. aegypti genome consists of transposable elements. These contribute to a factor of approximately 4 to 6 increase in average gene length and in sizes of intergenic regions relative to An. gambiae and Drosophila melanogaster. Nonetheless, chromosomal synteny is generally maintained among all three insects, although conservation of orthologous gene order is higher (by a factor of approximately 2) between the mosquito species than between either of them and the fruit fly. An increase in genes encoding odorant binding, cytochrome P450, and cuticle domains relative to An. gambiae suggests that members of these protein families underpin some of the biological differences between the two mosquito species.     

基于BP神经网络模型的果实蝇自动分类系统

果实蝇属昆虫危害水果和蔬菜,造成产量下降,影响对外贸易,对其识别是检疫工作中的重要部分,现有的人工辨识方法受时间、知识等因素影响不能准确、有效辨识。提出了一种基于BP神经网络模型的果实蝇分类方法,采用几何形态测量学中的标记点法对果蝇翅进行特征提取,通过方差分析确定了用于果蝇鉴定的11个主特征,建立3层BP神经网络模型,结合Levenberg-Marquardt BP训练函数对数据集进行训练,得到完整的可用于果实蝇分类的BP神经网络。实验表明,该方法能够对实蝇进行有效的辨识,对桔小实蝇、瓜实蝇、具条实蝇和南亚果实蝇等高风险果实蝇辨识的准确率分别是90.0%、93.3%、90.0%和96.7%,总体准确率为92.5%,具有良好的应用前景。     

Dual activation of the Drosophila toll pathway by two pattern recognition receptors

The Toll-dependent defense against Gram-positive bacterial infections in Drosophila is mediated through the peptidoglycan recognition protein SA (PGRP-SA). A mutation termed osiris disrupts the Gram-negative binding protein 1 (GNBP1) gene and leads to compromised survival of mutant flies after Gram-positive infections, but not after fungal or Gram-negative bacterial challenge. Our results demonstrate that GNBP1 and PGRP-SA can jointly activate the Toll pathway. The potential for a combination of distinct proteins to mediate detection of infectious nonself in the fly will refine the concept of pattern recognition in insects.     

作物抗虫育种的研究进展

作物的抗虫能力是其本身经过长期进化形成的一套防卫体系，具有潜在的利用价值．我国几十年的抗虫育种实践可以分为形态学抗虫育种、生化抗虫育种和基因工程抗虫育种3个阶段．作物的抗虫性同其它性状一样，是能够遗传的．现代生物技术的发展，为抗虫育种工作的深入提供了技术支持，丰富的植物种质资源为筛选优异的抗虫材料奠定了基础．通过基因工程途径创造抗虫的基因工程植株，并与常规育种相结合，必将培育出性状优良的抗虫新品种，并应用于农业生产．     

Secreted peptide Dilp8 coordinates Drosophila tissue growth with developmental timing

Little is known about how organ growth is monitored and coordinated with the developmental timing in complex organisms. In insects, impairment of larval tissue growth delays growth and morphogenesis, revealing a coupling mechanism. We carried out a genetic screen in Drosophila to identify molecules expressed by growing tissues participating in this coupling and identified dilp8 as a gene whose silencing rescues the developmental delay induced by abnormally growing tissues. dilp8 is highly induced in conditions where growth impairment produces a developmental delay. dilp8 encodes a peptide for which expression and secretion are sufficient to delay metamorphosis without affecting tissue integrity. We propose that Dilp8 peptide is a secreted signal that coordinates the growth status of tissues with developmental timing.     

Stable integration and expression of a bacterial gene in the mosquito Anopheles gambiae

Foreign DNA was successfully introduced into the germline of the African mosquito vector of malaria Anopheles gambiae. Stable integration of genes into the germlines of insects had been achieved previously only in Drosophila melanogaster and related species and required the use of the P element transposon. In these experiments with Anopheles gambiae, the plasmid pUChsneo was used, which contains the selectable marker neo gene flanked by P element inverted repeats. Mosquitoes injected with this plasmid were screened for resistance to the neomycin analog G-418. A single event of plasmid insertion was recovered. Integration appears to be stable and, thus far, resistance to G-418 has been expressed for eight generations. The transformation event appears to be independent of P.     

中国农业昆虫基因组学研究概况与展望

昆虫种类繁多,变异惊人,是地球上最大的动物类群,其中不少种类是农业上的重要害虫或益虫。自从2000年黑腹果蝇（Drosophila melanogaster）基因组发表以来,当代的昆虫学研究已经越来越多地依赖于从基因组和转录组所获得的信息。为了更好地理解昆虫生物学特性和增强应对那些严重影响人类健康、粮食供应和经济安全的各种卫生、农林害虫的能力,更好地利用那些在维持自然和农业生态系统不可或缺的昆虫以及那些为人类提供丝、蜂蜜和药品的昆虫,需要了解它们的基因组和转录组信息。目前世界上已经有50多种昆虫的基因组被报道,近10年来中国科学家也已经完成了家蚕（Bombyx mori）、小菜蛾（Plutella xyllostella）、东亚飞蝗（Locusta migratoria manilensis）、榕小蜂（Ceratosolen solmsi）和褐飞虱（Nilaparvata lugens）的基因组测定和分析,还有一批重要农业昆虫的基因组正在分析中,这其中包括烟粉虱（Bemisia tabaci）、斜纹夜蛾（Spodoptera litura）、二化螟（Chilo suppressalis）、白背飞虱（Sogatella furcifera）、灰飞虱（Laodelphax striatellu）和若干寄生蜂种类。自从2010年中国率先在国际上报道了2种昆虫（烟粉虱和褐飞虱）的转录组和表达谱以来,短短几年仅国内就已经有上百个昆虫转录组得到分析。同时,家蚕、东亚飞蝗和褐飞虱的功能基因组研究也取得了很大的进展, 例如,用40个品系重测序揭示了家蚕在驯化过程中相关的基因变化,通过信号通路分析解析了东亚飞蝗散居型和群居型转换的分子机制,以及发现了2个胰岛素受体是控制稻飞虱长、短翅型可塑性发育的“分子开关”。在基因组和转录组基础上,通过基因功能的研究和挖掘,结合应用新的基因组定点编辑技术和RNAi技术,将使害虫的防治和益虫的利用出现革命性的变化。     

人工神经网络对果蝇鸣声的分类识别

为了利用昆虫鸣声对昆虫进行种间或种下分类,对实验室环境下同种2个不同品系黑腹果蝇的飞行翅振鸣声进行了采集、分析,提取鸣声信号特征参数,并利用人工神经网络对采集的果蝇鸣声信号进行分类识别。结果表明,2个品系果蝇鸣声的基频均为236.86 Hz,有多个谐频,频率范围为0~4000 Hz,重叠较大;所建立的人工神经网络对种内不同品系果蝇鸣声的正确识别率均在75%以上,识别效果很好。研究结果为果蝇种下分类提供了新的方法和依据。     

FLP/FRT位点特异性重组系统在高等真核生物中的研究进展

 来源于酵母2 μm质粒的FLP/FRT位点特异性重组系统已经被广泛应用于拟南芥、水稻、小鼠、果蝇、线虫等高等真核模式生物,正逐渐成为转基因动植物研究领域进行基因操作的强有力工具。笔者综述了FLP/FRT系统的重组原理及其在高等真核生物中的应用,系统地概述了该系统在转基因植物、哺乳动物、昆虫以及其它相关高等真核模式生物中的研究现状,讨论了FLP/FRT系统在研究中存在的主要问题、应用前景和发展方向。