Maintenance of adaptive differentiation by Wolbachia induced bidirectional cytoplasmic incompatibility: the importance of sib-mating and genetic systems

<p>Abstract</p> <p>Background</p> <p>Bacteria of the genus <it>Wolbachia </it>are reproductive parasites widespread among arthropods. The most common effect arising from the presence of <it>Wolbachia </it>in a population is Cytoplasmic Incompatibility (CI), whereby postmating reproductive isolation occurs in crosses between an infected male and an uninfected female, or when a male is infected with a different strain of <it>Wolbachia </it>to that of the female (bidirectional CI). Previous theoretical models have demonstrated that bidirectional CI can contribute to the genetic divergence of populations in haploid and diploid organisms. However, haplodiploid organisms were not considered in these models even though they include <it>Nasonia </it>parasitoid wasps – the best example of the implication of <it>Wolbachia </it>in ongoing speciation. Moreover, previous work did not investigate inbreeding mating systems, which are frequently observed in arthropod species.</p> <p>Results</p> <p>We developed a stochastic two-island model which simulated three genetic scenarios, diploidy, haploidy, and haplodiploidy, with two CI phenotypes being considered for the latter: (1) male development of female progeny; and (2) mortality of fertilized eggs. We also investigated the effect of varying the proportion of sib mating. In the model each allopatric population was initially fixed for a single allele at a nuclear locus under positive selection and infected with one strain of <it>Wolbachia</it>. Each simulation presupposed that the two populations were fixed for a different allele and a different strain of <it>Wolbachia</it>. The degree of genetic differentiation observed in the locus under selection due to bidirectional CI was much lower for the two haplodiploid phenotypes than for either diploids or haploids. Furthermore, we demonstrated that sib-mating may compensate for the lower efficiency of bidirectional CI in haplodiploids by maintaining genetic divergence.</p> <p>Conclusion</p> <p>Our model suggests that maintenance of genetic differentiation facilitated by <it>Wolbachia </it>is more likely to occur in diploids and haploids than in haplodiploids. However, increasing the level of sib-mating may compensate for the weak effect of bidirectional CI in haplodiploids. Our work therefore gives a potential explanation for why the haplodiploid <it>Nasonia </it>species, which are infected with bidirectionally incompatible <it>Wolbachia </it>strains and undergo sib-mating, have differentiated genetically and maintained this differentiation without premating isolation.</p

Phylogenomic analysis of protein-coding genes resolves complex gall wasp relationships

International audienceAbstract Gall wasps (Hymenoptera: Cynipidae) comprise 13 distinct tribes whose interrelationships remain incompletely understood. Recent analyses of ultra‐conserved elements (UCEs) represent the first attempt at resolving these relationships using phylogenomics. Here, we present the first analysis based on protein‐coding sequences from genome and transcriptome assemblies. Unlike UCEs, these data allow more sophisticated substitution models, which can potentially resolve issues with long‐branch attraction. We include data for 37 cynipoid species, including two tribes missing in the UCE analysis: Aylacini (s. str.) and Qwaqwaiini. Our results confirm the UCE result that Cynipidae are not monophyletic. Specifically, the Paraulacini and Diplolepidini + Pediaspidini fall outside a core clade (Cynipidae s. str.), which is more closely related to the insect‐parasitic Figitidae, and this result is robust to the exclusion of long‐branch taxa that could mislead the analysis. Given this, we here divide the Cynipidae into three families: the Paraulacidae stat. prom., Diplolepididae stat. prom. and Cynipidae (s. str.). Our results suggest that the Eschatocerini are the sister group of the remaining Cynipidae (s. str.). Within the Cynipidae (s. str.), the Aylacini (s. str.) are more closely related to oak gall wasps (Cynipini) and some of their inquilines (Ceroptresini) than to other herb gallers (Aulacideini and Phanacidini), and the Qwaqwaiini likely form a clade together with Synergini (s. str.) and Rhoophilini. Several alternative scenarios for the evolution of cynipid life histories are compatible with the relationships suggested by our analysis, but all are complex and require multiple shifts among parasitoids, inquilines and gall inducers

Гранитоиды обрамления Криворожской структуры. Проблемы корреляции геологических тел и комплексов

Current population genetic models fail to cope with genetic differentiation for species with large, contiguous and heterogeneous distribution. We show that in such a case, genetic differentiation can be predicted at equilibrium by circuit theory, where conductance corresponds to abundance in species distribution models (SDM). Circuit-SDM approach was used for the phylogeographic study of the lepidopteran cereal stemborer Busseola fusca Füller (Noctuidae) across sub-Saharan Africa. Species abundance was surveyed across its distribution range. SDM models were optimized and selected by cross validation. Relationship between observed matrices of genetic differentiation between individuals, and matrices of resistance distance was assessed through Mantel tests and redundancy discriminant analyses (RDA). A total of 628 individuals from 130 localities in 17 countries were genotyped at 7 microsatellite loci. Six population clusters were found based on a Bayesian analysis. The eastern margin of Dahomey Gap between East and West Africa was the main factor of genetic differentiation. The SDM projections at present, last interglacial and last glacial maximum periods were used for estimation of circuit resistance between locations of genotyped individuals. For all periods of time, when using either all individuals or only East-African individuals, partial Mantel r and RDA analyses conditioning on geographic distance were found significant. Under future projections (year 2080), partial r and RDA significance were different. From this study, it is concluded that analytical solutions provided by circuit theory are useful for the evolutionary management of populations and for phylogeographic analysis when coalescence times are not accessible by approximate Bayesian simulations

Fine-Scale Population Recombination Rates, Hotspots, and Correlates of Recombination in the Medicago truncatula Genome

Recombination rates vary across the genome and in many species show significant relationships with several genomic features, including distance to the centromere, gene density, and GC content. Studies of fine-scale recombination rates have also revealed that in several species, there are recombination hotspots, that is, short regions with recombination rates 10–100 greater than those in surrounding regions. In this study, we analyzed whole-genome resequence data from 26 accessions of the model legume Medicago truncatula to gain insight into the genomic features that are related to high- and low-recombination rates and recombination hotspots at 1 kb scales. We found that high-recombination regions (1-kb windows among those in the highest 5% of the distribution) on all three chromosomes were significantly closer to the centromere, had higher gene density, and lower GC content than low-recombination windows. High-recombination windows are also significantly overrepresented among some gene functional categories—most strongly NB–ARC and LRR genes, both of which are important in plant defense against pathogens. Similar to high-recombination windows, recombination hotspots (1-kb windows with significantly higher recombination than the surrounding region) are significantly nearer to the centromere than nonhotspot windows. By contrast, we detected no difference in gene density or GC content between hotspot and nonhotspot windows. Using linear model wavelet analysis to examine the relationship between recombination and genomic features across multiple spatial scales, we find a significant negative correlation with distance to the centromere across scales up to 512 kb, whereas gene density and GC content show significantly positive and negative correlations, respectively, only up to 64 kb. Correlations between recombination and genomic features, particularly gene density and polymorphism, suggest that they are scale dependent and need to be assessed at scales relevant to the evolution of those features

Diversification écologique du parasitoïde africain Cotesia sesamiae (rôle des partenaires symbiotiques)

Cotesia sesamiae est un parasitoïde de chenilles ravageuses du maïs et du sorgho. Les différentes populations de C. sesamiae ne possèdent pas la même capacité à se développer sur chacun des hôtes rencontrés. Elles possèdent un virus symbiotique intégré au génome et directement impliqué dans le contournement de la réponse immunitaire de l'hôte. L'étude chez le parasitoïde de plusieurs marqueurs microsatellites et d un marqueur du virus a permis de démontrer la corrélation entre le génotype viral et la spécialisation de C sesamiae sur son hôte. Les C. sesamiae sont aussi associées à des bactéries du genre Wolbachia. Ces bactéries sont à l'origine d'isolements post-copulatoires chez les insectes. Trois souches de Wolbachia hébergées par des populations distinctes ont été détectées chez C. sesamiae. Ce résultat suggère une implication des Wolbachia dans le renforcement de la sélection sur le virus. Un modèle théorique a été développé et démontre que l'isolement post-copulatoire engendré par Wolbachia ne semble pas être une force évolutive suffisante pour maintenir la divergence à un locus sous sélection. Les données de terrain confirment ce résultat.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Narcolepsy and the Dissociation of REM Sleep and Cataplexy through Ambient Temperature Manipulation

Narcolepsy is characterized by increased REM sleep propensity and cataplexy. Although narcolepsy is caused by the selective loss or dysfunction of hypocretin (Hcrt) neurons within the lateral hypothalamus (LH), mechanisms underlying REM sleep propensity and cataplexy remain to be elucidated. We have recently shown that wild type (WT) mice increase REM sleep expression when exposed to thermoneutral ambient temperature (Ta) warming during the light (inactive) phase. We hypothesized that the loss of Hcrt may lead to exaggerated responses with respect to increased REM sleep and cataplexy during Ta warming. To test this hypothesis, Hcrt-KO mice were implanted for chronic sleep recordings and housed in a temperature-controlled cabinet. Sleep-wake expression and both spontaneous cataplexy and food-elicited cataplexy were evaluated at constant Ta and during a Ta manipulation protocol. Here we show several unexpected findings. First, Hcrt-KO mice show opposite circadian patterns with respect to REM sleep responsiveness to thermoneutral Ta warming compared to WT mice. As previous demonstrated, WT mice increased REM sleep when Ta warming is presented during the inactive (light) phase, whereas Hcrt-KO showed a significant decrease in REM sleep expression. In contrast, Hcrt-KO mice increased REM sleep expression upon exposure to Ta warming when presented during the active (dark) phase, a circadian time when WT mice showed no significant changes in REM sleep as a function of Ta. Second, we found that REM sleep and cataplexy can be dissociated through Ta manipulation. Specifically, although Ta warming significantly increased REM sleep expression in Hcrt-KO mice during the active phase, cataplexy bout number and total cataplexy duration significantly decreased. In contrast, cataplexy expression was favoured during Ta cooling when REM sleep expression significantly decreased. Finally, video actigraphy and sleep-wake recordings in Hcrt-KO mice demonstrated that Ta manipulation did not significantly alter waking motor activity patterns or waking or NREM sleep durations. These data suggest that neural circuits gating REM sleep and cataplexy expression can be dissociated with Ta manipulation

Data_greenhouse_genotypes_relatedness_analyse

Genotype data of greenhouse fungal strains used for relatedness analysis. Genotypes based on micorsatellite markers