寄生蜂体内共生菌Wolbachia研究进展

Wolbachia是广泛分布在节肢动物生殖组织中的细胞质遗传细菌,在寄生蜂中可以通过诱导胞质不亲和、孤雌生殖、雄性雌性化和杀雄等多种方式调节寄主的生殖.本文在综述了寄生蜂体内共生菌Wolbachia的类群和分化、传播方式及其对寄主生物学特性的影响、温度通过对Wolbachia的作用而影响寄生蜂的表现等基础上,讨论了如何...     

沃尔巴克氏体Wolbachia对宿主的生殖调控作用及其研究进展

沃尔巴克氏体Wolbachia是广泛分布于节肢动物体内的共生微生物,可通过宿主卵的细胞质传递给子代。Wolbachia通过多种方式调控其宿主的生殖活动,包括细胞质不亲和、孤雌生殖、雌性化、杀雄性和增强雄性或雌性的生殖力。通过这些调控作用促进其在宿主种群内的广泛传播。文章简要综述Wolbachia对宿主的生殖调控作用、水平传播、Wolbachia基因和应用方面的研究。     

共生菌Wolbachia引起宿主细胞质不亲和的研究进展

Wolbachia是一类广泛存在于节肢动物以及线虫体内细胞质中呈母系遗传的共生细菌,能够在宿主中产生细胞质不亲和、孤雌生殖、雌性化及杀雄等多种生殖调控作用,其中细胞质不亲和是指被Wolbachia感染的雄性个体与未感染的雌性个体(单向不亲和),或者感染不同株系Wolbachia的雌性个体(双向不亲和)交配后不能或很少产生后代,或者后代偏雄性的现象。细胞质不亲和作用使感染的雌性个体在种群中具有很大的生殖优势,凭借这种生殖优势,Wolbachia能够迅速在宿主种群中扩张。细胞质不亲和的机理探索主要集中在细胞学水平上,其中广为接受的精子"修饰"和"拯救"理论认为,精巢中的Wolbachia能够修饰宿主的精细胞,使其不能和卵细胞正常融合,但是当母本感染相同的Wolbachia时,就能够将"修饰"过的精子细胞"拯救"过来,使其恢复与卵细胞的正常融合。而分子机理上的探索也开始在转录组、基因组和miRNA水平上对部分昆虫展开了研究。影响细胞质不亲和的因素有很多,包括宿主遗传背景、Wolbachia株系、Wolbachia基因型、共生菌密度(浓度、滴度)、雄虫年龄、环境因素以及共生菌在宿主生殖组织的分布等。近年来,人类也应用细胞质不亲和控制害虫(主要是蚊虫)和人类疾病,取得了较好的进展。     

Wolbachia与昆虫寄主关系研究进展

Wolbachia pipientis是一种广泛存在于节肢动物和线虫生殖组织中的细胞内共生菌,通过母系生殖细胞在寄主种群内垂直传播。据分析,Wolbachia在昆虫中的感染率大约为66%,是昆虫中分布最广泛的胞内共生菌。Wolbachia能够以多种方式调控寄主的生殖行为,包括诱导细胞质不亲和、诱导孤雌生殖、雌性化、杀雄作用等。近10年来,Wolbachia的研究在多个领域都取得了长足进展。本文介绍了Wolbachia的多样性与分布、对寄主生殖行为的影响、基因组结构,以及其与寄主在基因组水平上的相互作用等领域的最新研究成果,并展望了Wolbachia研究的发展趋势。     

棉蚜体内感染沃尔巴克氏体（Wolbachia）的分子检测

Wolbachia是存在于节肢动物体内的一类呈母系遗传的细胞内共生细菌 ,这类细菌可以通过卵的细胞质传播并参与调控寄主的生殖活动。通过对Wolbachia外膜蛋白质的wsp基因进行特异性扩增 ,证实了寄生于不同植物的棉蚜 (AphisgossypiiGlover)体内均有感染 ,说明Wolbachia可能广泛存在于棉蚜体内 ,扩增出的Wolbachia目的片段为 5 90bp左右。通过对棉蚜体内感染的Wolbachia的wsp基因序列进行分子检测 ,为进一步研究棉蚜的孤雌生殖与Wolbachia的相关关系等奠定基础。     

Wolbachia在熊蜂中的双重感染

Wolbachia是一类广泛存在于节肢动物体内细胞质遗传的细菌,它可以通过诱导产雌孤雌生殖、引起细胞质不亲和、遗传雄性的雌性化、雄性致死和增强生殖力等作用方式引起其寄主生殖行为的改变.本文以16S rDNA为标记检测了3种熊蜂不同组织(头,胸,足,卵巢或雄外生殖器)的Wolbachia感染.其中明亮熊蜂Bombus l...     

Wolbachia属共生菌及其对节肢动物宿主适合度的影响

Wolbachia是广泛分布于节肢动物体生殖组织内呈母质遗传的一类共生细菌。近30多年来,大量的研究主要集中于Wolbachia对宿主生殖方式的调控方面;近年来的研究发现,Wolbachia对节肢动物宿主的适合度具有不同程度的影响。现对Wolbachia的宿主分布、存在部位及其对节肢动物宿主种群适合度的影响等方面进行了综述,探讨了Wolbachia在该领域的研究意义和潜在的应用价值。     

首次发现扶桑绵粉蚧体内存在沃尔巴克氏体

沃尔巴克氏体(Wolbachia)是广泛分布在节肢动物生殖组织中的一类细胞质遗传的细菌，它们可以调控宿主的生殖活动。利用沃尔巴克氏体wsp基因的1对通用引物(81F，691R)从新入侵我国的扶桑绵粉蚧Phenacoccus solenopsis Tinsley雌成虫的总DNA中扩增到1个550 bp左右的片段，并克隆得到了Wolbachia的wsp基因序列，首次发现了沃尔巴克氏体对扶桑绵粉蚧的感染现象。     

果蝇细胞内共生菌Wolbachia研究进展

Wolbachia是一类存在于包括绝大多数昆虫在内的节肢动物以及线虫体内的细胞内共生菌,通过母系传递给子代。该菌能以多种方式调控宿主的生殖活动,包括诱导细胞质不亲和、孤雌生殖、杀雄、雌性化和增加雌性生殖力。本文对Wolbachia的基础生物学及其分布、以及该菌对宿主果蝇的影响等进行了评述,并对与果蝇相关的Wolbachia的研究现状及趋势进行了讨论。     

我国烟粉虱自然种群中存在广泛的Wolbachia感染现象

Wolbachia是广泛分布于节肢动物生殖组织中的细胞质遗传的一类共生菌,可以引起宿主生殖行为的改变.烟粉虱是重要的农业害虫,已有的研究表明烟粉虱中存在Wolbachia的感染,但所检测到的感染率不高,并且迄今在烟粉虱中所检出的Wolbachia均属于B组群.该研究从我国河北、新疆、北京、山东、浙江、广西、海南、广州和福建采集到18个烟粉虱地理种群,首先基于ITS1 rDNA克隆测序鉴定了烟粉虱的生物型,然后采用自行设计的Wolbachia 16S rDNA及wsp基因的专用引物对所采集到的烟粉虱种群进行了分子检测.结果表明几乎所有的烟粉虱自然种群中都存在Wolbachia感染,同时还发现B/Q生物型烟粉虱中主要感染A组群Wolbachia,而非B/Q生物型烟粉虱中存在大量的超感染现象.该研究显示烟粉虱自然种群中Wolbachia的感染率比预想的要高得多,而分子检测方法的灵敏度可能是影响Wolbachia感染率研究的关键因素之一.     

Diversity of Wolbachia isolated from the Cubitermes sp. affinis subarquatus complex of species (Termitidae), revealed by multigene phylogenies

Wolbachia are endosymbiotic bacteria that may alter the reproductive mechanisms of arthropod hosts. Eusocial termites provide considerable scope for Wolbachia studies owing to their ancient origin, their great diversity and their considerable ecological, biological and behavioral plasticity. This article describes the phylogenetic distribution of Wolbachia infecting termites of the Cubitermes genus, which are particularly abundant soil-feeders in equatorial Africa. Fourteen colonies of the Cubitermes sp. affinis subarquatus complex of species were screened using five bacterial genes (wsp, ftsZ, coxA, fbpA and 16S rRNA genes) and a striking diversity of Wolbachia strains was identified within these closely related species. In the host complex, three Wolbachia variants were found that were not in the super groups usually reported for termites (F and H), each infecting one or two Cubitermes species.     

How many species are infected with Wolbachia? Cryptic sex ratio distorters revealed to be common by intensive sampling.

Inherited bacterial symbionts from the genus Wolbachia have attracted much attention by virtue of their ability to manipulate the reproduction of their arthropod hosts. The potential importance of these bacteria has been underlined by surveys, which have estimated that 17% of insect species are infected. We examined whether these surveys have systematically underestimated the proportion of infected species through failing to detect the low-prevalence infections that are expected when Wolbachia distorts the sex ratio. We estimated the proportion of species infected with Wolbachia within Acraea butterflies by testing large collections of each species for infection. Seven out of 24 species of Acraea were infected with Wolbachia. Four of these were infected with Wolbachia at high prevalence, a figure compatible with previous broad-scale surveys, whilst three carried low-prevalence infections that would have had a very low likelihood of being detected by previous sampling methods. This led us to conclude that sex-ratio-distorting Wolbachia may be common in insects that have an ecology and/or genetics that permit the invasion of these parasites and that previous surveys may have seriously underestimated the proportion of species that are infected.     

Hidden Wolbachia diversity in field populations of the European cherry fruit fly, Rhagoletis cerasi (Diptera, Tephritidae)

The European cherry fruit fly Rhagoletis cerasi has been a field model for cytoplasmic incompatibility since the mid 1970s. Two Wolbachia strains were detected in this tephritid species and w Cer2 was described as the CI inducing agent dividing European populations into two unidirectional incompatible groups, i.e. southern females produce viable offspring with northern males, whereas the reciprocal cross results in incompatibility. We detected three new Wolbachia strains by sequencing a multitude of plasmids derived from Wolbachia surface protein gene ( wsp ) polymerase chain reaction (PCR) products. Strain-specific primers were developed allowing individual diagnosis without need for cloning. Hybridization of specific PCR products with a wsp oligonucleotide enhanced the detection limit significantly and revealed the presence of low-titre infections in some strains, in different ontogenetic stages and in adults of different age. We then performed a survey of strain prevalence and infection frequency in eight European regions. w Cer1 was fixed in all populations, whereas w Cer2 was detected only in the South. w Cer3 frequency was the lowest without a clear distribution pattern. The abundance of w Cer4 was homogenous across Europe. Like w Cer2, w Cer5 showed significant differences in spatial distribution. Our new findings of previously undetected and recombinant Wolbachia strains in R. cerasi reveal a major caveat to the research community not to overlook hidden Wolbachia diversity in field populations. Low-titres and geographical variability in Wolbachia diversity are expected to influence the outcome of Wolbachia population dynamics and Wolbachia- based insect population control and may create invasion barriers for expanding and artificially introduced Wolbachia strains.     

Genotypic diversity of Wolbachia pipientis in native and invasive Harmonia axyridis Pall., 1773 (Coleoptera,Coccinellidae) populations

The distribution and variability of reproductive symbiotic Wolbachia pipientis bacteria were studied in seven native and six invasive H. axyridis populations. Wolbachia-infected individuals were found in two invasive and two native populations. We demonstrated for the first time an infection of invasive H. axyridis populations with Wolbachia. Two new molecular forms of Wolbachia were detected by a system of multilocus typing. The supergroup A Wolbachia was found for the first time in H. axyridis. The detected genotypic diversity of Wolbachia indicates repeated and independent infection events in the evolutionary past of H. axyridis.     

Wolbachia在花蓟马中的感染及其与寄主线粒体DNA多样性的关系

【目的】Wolbachia是一种广泛存在于节肢动物中的胞内共生细菌,影响寄主的生物学特性。花蓟马Frankliniella intonsa(Trybom)是重要的害虫,对农作物及园林植物造成危害。本研究旨在明确Wolbachia在花蓟马中的感染情况,并分析其与寄主线粒体DNA多样性的关系。【方法】采集中国境内26个花蓟马自然种群,运用多位点序列分型技术(multilocus sequence typing,MLST)对其体内Wolbachia感染率及株系进行分析;利用线粒体COI分子标记研究花蓟马的遗传分化及遗传多样性;通过比较感染和未感染Wolbachia个体COI数据,探究Wolbachia多样性与寄主线粒体DNA多样性之间的关系。【结果】花蓟马中Wolbachia的感染率为0%~60%,共检测到5种Wolbachia株系(w Fint1,w Fint2,w Fint3,w Fint4及w Fint5),均属于B大组且形成一个单系群。Wolbachia感染情况与这些花蓟马种群(除CC,GZ,TA和TY,N5)的线粒体DNA多样性相关,表现为不感染Wolbachia的种群中线粒体DNA单倍型多样性(Hd)与核苷酸多样性(Pi)均高于感染Wolbachia的种群,且Wolbachia感染率与Hd呈显著负相关(P0.05)。AMOVA分析表明花蓟马线粒体DNA遗传分化与Wolbachia感染情况有关。【结论】Wolbachia可能在侵染花蓟马种群后出现遗传分化;Wolbachia感染与寄主线粒体DNA多样性有关。     

Wolbachia infections in the Cimicidae: museum specimens as an untapped resource for endosymbiont surveys

Wolbachia spp. are obligate maternally inherited endosymbiotic bacteria that infect diverse arthropods and filarial nematodes. Previous microscopic and molecular studies have identified Wolbachia in several bed bug species (Cimicidae), but little is known about how widespread Wolbachia infections are among the Cimicidae. Because cimicids of non-medical importance are not commonly collected, we hypothesized that preserved museum specimens could be assayed for Wolbachia infections. For the screening of museum specimens, we designed a set of primers that specifically amplify small diagnostic fragments (130 to 240 bp) of the Wolbachia 16S rRNA gene. Using these and other previously published primers, we screened 39 cimicid species (spanning 16 genera and all 6 recognized subfamilies) and 2 species of the sister family Polyctenidae for Wolbachia infections using museum and wild-caught material. Amplified fragments were sequenced to confirm that our primers were amplifying Wolbachia DNA. We identified 10 infections, 8 of which were previously undescribed. Infections in the F supergroup were common in the subfamily Cimicinae, while infections in the A supergroup were identified in the subfamilies Afrocimicinae and Haematosiphoninae. Even though specimens were degraded, we detected infections in over 23% of cimicid species. Our results indicate that Wolbachia infections may be common among cimicids and that archived museum material is a useful untapped resource for invertebrate endosymbiont surveys. The new screening primers listed in this report will be useful for other researchers conducting Wolbachia surveys with specimens with less-than-optimum DNA quality.     

Modes of acquisition of Wolbachia: horizontal transfer, hybrid introgression, and codivergence in the Nasonia species complex

Wolbachia are maternally inherited bacteria that infect a large number of insects and are responsible for different reproductive alterations of their hosts. One of the key features of Wolbachia biology is its ability to move within and between host species, which contributes to the impressive diversity and range of infected hosts. Using multiple Wolbachia genes, including five developed for Multi-Locus Sequence Typing (MLST), the diversity and modes of movement of Wolbachia within the wasp genus Nasonia were investigated. Eleven different Wolbachia were found in the four species of Nasonia , including five newly identified infections. Five infections were acquired by horizontal transmission from other insect taxa, three have been acquired by hybridization between two Nasonia species, which resulted in a mitochondrial- Wolbachia sweep from one species to the other, and at least three have codiverged during speciation of their hosts. The results show that a variety of transfer mechanisms of Wolbachia are possible even within a single host genus. Codivergence of Wolbachia and their hosts is uncommon and provides a rare opportunity to investigate long-term Wolbachia evolution within a host lineage. Using synonymous divergence among codiverging infections and host nuclear genes, we estimate Wolbachia mutation rates to be approximately one-third that of the nuclear genome.     

Diversity and recombination in <Emphasis Type="Italic">Wolbachia</Emphasis> and <Emphasis Type="Italic">Cardinium</Emphasis> from <Emphasis Type="Italic">Bryobia</Emphasis>spider mites

BACKGROUND: Wolbachia and Cardinium are endosymbiotic bacteria infecting many arthropods and manipulating host reproduction. Although these bacteria are maternally transmitted, incongruencies between phylogenies of host and parasite suggest an additional role for occasional horizontal transmission. Consistent with this view is the strong evidence for recombination in Wolbachia, although it is less clear to what extent recombination drives diversification within single host species and genera. Furthermore, little is known concerning the population structures of other insect endosymbionts which co-infect with Wolbachia, such as Cardinium. Here, we explore Wolbachia and Cardinium strain diversity within nine spider mite species (Tetranychidae) from 38 populations, and quantify the contribution of recombination compared to point mutation in generating Wolbachia diversity. RESULTS: We found a high level of genetic diversity for Wolbachia, with 36 unique strains detected (64 investigated mite individuals). Sequence data from four Wolbachia genes suggest that new alleles are 7.5 to 11 times more likely to be generated by recombination than point mutation. Consistent with previous reports on more diverse host samples, our data did not reveal evidence for co-evolution of Wolbachia with its host. Cardinium was less frequently found in the mites, but also showed a high level of diversity, with eight unique strains detected in 15 individuals on the basis of only two genes. A lack of congruence among host and Cardinium phylogenies was observed. CONCLUSIONS: We found a high rate of recombination for Wolbachia strains obtained from host species of the spider mite family Tetranychidae, comparable to rates found for horizontally transmitted bacteria. This suggests frequent horizontal transmission of Wolbachia and/or frequent horizontal transfer of single genes. Our findings strengthens earlier reports of recombination for Wolbachia, and shows that high recombination rates are also present on strains from a restrictive host range. Cardinium was found co-infecting several spider mite species, and phylogenetic comparisons suggest also horizontal transmission of Cardinium among hosts.     

Multiple introductions of the Spiroplasma bacterial endosymbiont into Drosophila

Bacterial endosymbionts are common in insects and can have dramatic effects on their host's evolution. So far, the only heritable symbionts found in Drosophila have been Wolbachia and Spiroplasma . While the incidence and effects of Wolbachia have been studied extensively, the prevalence and significance of Spiroplasma infections in Drosophila are less clear. These small, gram-positive, helical bacteria infect a diverse array of plant and arthropod hosts, conferring a variety of fitness effects. Male-killing Spiroplasma are known from certain Drosophila species; however, in others, Spiroplasma appear not to affect sex ratio. Previous studies have identified different Spiroplasma haplotypes in Drosophila populations, although no extensive surveys have yet been reported. We used a multilocus sequence analysis to reconstruct a robust Spiroplasma endosymbiont phylogeny, assess genetic diversity, and look for evidence of recombination. Six loci were sequenced from over 65 Spiroplasma -infected individuals from nine different Drosophila species. Analysis of these sequences reveals at least five separate introductions of four phylogenetically distinct Spiroplasma haplotypes, indicating that more extensive sampling will likely reveal an even greater Spiroplasma endosymbiont diversity. Patterns of variation in Drosophila mitochondrial haplotypes in Spiroplasma -infected and uninfected flies imply imperfect vertical transmission in host populations and possible horizontal transmission.