Induction of a Peptide with Activity against a Broad Spectrum of Pathogens in the Aedes aegypti Salivary Gland, following Infection with Dengue Virus

The ultimate stage of the transmission of Dengue Virus (DENV) to man is strongly dependent on crosstalk between the virus and the immune system of its vector Aedes aegypti (Ae. aegypti). Infection of the mosquito's salivary glands by DENV is the final step prior to viral transmission. Therefore, in the present study, we have determined the modulatory effects of DENV infection on the immune response in this organ by carrying out a functional genomic analysis of uninfected salivary glands and salivary glands of female Ae. aegypti mosquitoes infected with DENV. We have shown that DENV infection of salivary glands strongly up-regulates the expression of genes that encode proteins involved in the vector's innate immune response, including the immune deficiency (IMD) and Toll signalling pathways, and that it induces the expression of the gene encoding a putative anti-bacterial, cecropin-like, peptide (AAEL000598). Both the chemically synthesized non-cleaved, signal peptide-containing gene product of AAEL000598, and the cleaved, mature form, were found to exert, in addition to antibacterial activity, anti-DENV and anti-Chikungunya viral activity. However, in contrast to the mature form, the immature cecropin peptide was far more effective against Chikungunya virus (CHIKV) and, furthermore, had strong anti-parasite activity as shown by its ability to kill Leishmania spp. Results from circular dichroism analysis showed that the immature form more readily adopts a helical conformation which would help it to cause membrane permeabilization, thus permitting its transfer across hydrophobic cell surfaces, which may explain the difference in the anti-pathogenic activity between the two forms. The present study underscores not only the importance of DENV-induced cecropin in the innate immune response of Ae. aegypti, but also emphasizes the broad-spectrum anti-pathogenic activity of the immature, signal peptide-containing form of this peptide

When recurrent hybridization obscures phylogenetic hypotheses, the case of Chrysocarabus beetles

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From refugia to contact: Pine processionary moth hybrid zone in a complex biogeographic setting

Contact zones occur at the crossroad between specific dispersal routes and are facilitated by biogeographic discontinuities. Here, we focused on two Lepidoptera sister species that come in contact near the Turkish Straits System (TSS). We aimed to infer their phylogeographic histories in the Eastern Mediterranean and finely analyze their co-occurrence and hybridization patterns in this biogeographic context. We used molecular mitochondrial and nuclear markers to study 224 individuals from 42 localities. We used discordances between markers and complementary assignment methods to identify and map hybrids and parental individuals. We confirmed the parapatric distribution of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) in the west and Thaumetopoea wilkinsoni in the east and identified a narrow contact zone. We identified several glacial refugia of T. wilkinsoni in southern Turkey with a strong east-west differentiation in this species. Unexpectedly, T. pityocampa crossed the TSS and occur in northern Aegean Turkey and some eastern Greek islands. We found robust evidence of introgression between the two species in a restricted zone in northwestern Turkey, but we did not identify any F-1 individuals. The identified hybrid zone was mostly bimodal. The distributions and genetic patterns of the studied species were strongly influenced both by the Quaternary climatic oscillations and the complex geological history of the Aegean region. T. pityocampa and T. wilkinsoni survived the last glacial maximum in disjoint refugia and met in western Turkey at the edge of the recolonization routes. Expanding population of T. wilkinsoni constrained T. pityocampa to the western Turkish shore. Additionally, we found evidence of recurrent introgression by T. wilkinsoni males in several T. pityocampa populations. Our results suggest that some prezygotic isolation mechanisms, such as differences in timing of the adult emergences, might be a driver of the isolation between the sister species

Isolation, characterization and PCR multiplexing of microsatellite loci for a mite crop pest, Tetranychus urticae (Acari: Tetranychidae)

International audienceBackground: Tetranychus urticae is a highly polyphagous species with a cosmopolitan distribution that has the status of pest in more than 100 economically significant crops all over the world. Despite a number of previous effortsto isolate genetic markers, only a reduced set of microsatellite loci has been published. Taking advantage of the whole genome sequence of T. urticae that recently became available; we isolated and characterized a new set of microsatellite loci and tested the level of polymorphism across populations originating from a wide geographical area. Results: A total of 42microsatellite sequences widespread in the T. urticae genome were identified, the exact position in the genome recorded, and PCR amplification of microsatellite loci tested with primers defined here. Fourteen loci showed unambiguous genotype patterns and were further characterized. Three multiplex polymerase chain reaction sets were optimized in order to genotype a total of 24 polymorphic loci, including 10 previously published Tetranychus-specific loci. The microsatellite kits successfully amplified 686 individuals from 60 field populations for which we assessed the level of genetic diversity. The number of alleles per locus ranged from 3 to 16 and the expected heterozygosity values ranged from 0.12 to 0.81. Most of the loci displayed a significant excess of homozygous and did not model the Hardy–Weinberg equilibrium. This can be explained by the arrhenotokous mode of reproduction of T. urticae. Conclusions: These primers represent a valuable resource for robust studies on the genetic structure, dispersal and population biology of T. urticae, that can be used in managing this destructive agricultural pest

Pushing the limits of whole genome amplification: successful sequencing of RADseq libraries from single micro-hymenoptera (Chalcidoidea, Trichogramma)

A major obstacle to high-throughput genotyping of micro-hymenoptera is their small size. As species are difficult to discriminate and because complexes may exist, the sequencing of a pool of specimens is hazardous. Thus, one should be able to sequence pangenomic markers (e.g. RADtags) from a single specimen. To date, whole genome amplification (WGA) prior to library construction is still a necessity as only ca 10ng of DNA can be obtained from single specimens. However this amount of DNA is not compatible with manufacturer’s requirements for commercialised kits. Here we tested the accuracy of the GenomiPhi kit V2 on Trichogramma wasps by comparing RAD libraries obtained from the WGA of single specimens (generation F0 and F1, ca 1 ng input DNA for the WGA) and a biological amplification of genomic material (the pool of the progeny of the F1 generation). Globally, we found that ca 99% of the examined loci (up to 48,189; 109 bp each) were compatible with the mode of reproduction of the studied model (haplodiploidy) or a Mendelian inheritance of alleles. The remaining 1% (ca 0.01% of the analysed nucleotides) could represent WGA bias or other experimental / analytical bias. This study shows that the multiple displacement amplification method on which the GenomiPhi kit relies, could also be of great help for the high-throughput genotyping of micro-hymenoptera used for biological control or other organisms from which only a very low amount of DNA can be extracted such as human disease vectors (e.g. sand flies, fleas, ticks etc.)

Understanding the origin of invasive populations of the pine processionary moth: a population genetic approach

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Isolation and characterization of 15 microsatellite markers for the highly invasive box tree moth Cydalima perspectalis (Lepidoptera: Crambidae)

Article en open accessInternational audienceIn this study, we report the development of a set of 15 polymorphic microsatellite markers for the box tree moth, Cydalima perspectalis (Walker), a highly invasive insect in Europe causing significant damage to natural and ornamental Buxus trees. The markers were characterized for four distant populations in both its native (China, two populations) and invasive ranges (Czech Republic and Turkey, one population each). The number of alleles ranged from 2 to 12. No marker significantly deviated from the Hardy-Weinberg equilibrium for all the populations sampled. These microsatellite markers are promising tools for further studies on the invasive pathways and dispersal pattern of the box tree moth in Europe

From sympatry to parapatry: a rapid change in the spatial context of incipient allochronic speciation

Speciation is nowadays recognized as a dynamic process in which the respective roles of forces driving ecological differentiation and reproductive isolation can change through time and space. Incipient speciation events are particularly useful to follow such processes that are not tractable when considering well-differentiated taxa. A promising case study was discovered in the pine processionary moth, Thaumetopoea pityocampa, a Mediterranean defoliator of Pinus species, for which allochrony acting as an automatic magic trait was recognized as the major driver of an incipient speciation process. In Portugal, a unique population with a shifted phenology, known as the summer population (SP), co-occurs with a population following the typical life cycle, known as the winter population (WP). We monitored male activity of both populations in the Leiria region, i.e. over the whole SP distribution range using a systematic sampling along two transects, and studied Portuguese WPs at a larger geographical scale to explore their genetic diversity and spatial pattern of differentiation. Results showed that the WPs were genetically more diverse than the SP, with a strong pattern of isolation by distance both at large and small spatial scales, while the SP was very homogeneous over its whole range, without signature of its recent spatial expansion. Contrary to our expectations, no F1 hybrids were identified, even though we found an extended flight period of the SP, overlapping with the beginning of the WP reproductive period. Interestingly, the SP was found to be mostly limited to the sea shore where the WP is now scarce or absent, which could suggest competitive exclusion. Once clearly occurring in a sympatric context, the allochronic differentiation tends to develop nowadays in parapatry.Nouveaux outils statistiques pour l'analyse spatiale des données génétiquesMediterranean Center for Environment and Biodiversit

Crossing the Mid-Aegean Trench: vicariant evolution of the Eastern pine processionary moth, Thaumetopoea wilkinsoni (Lepidoptera: Notodontidae), in Crete

WOS: 000434110600009Thaumetopoea wilkinsoni Tams, 1924 occurs in the southeast Mediterranean basin and infests pine and cedar stands. Our objective was to decipher the biogeography of the species and, in particular, to explore its evolutionary history on the island of Crete. We collected 135 individuals from 14 sites on Crete, Turkey, Samos and Rhodes. We sequenced one mitochondrial fragment (cytochrome c subunit I) and used 12 microsatellite loci for population genetic analyses. All results supported the deep divergence of Cretan populations from the neighbouring areas, with the differentiation between Crete and neighbouring regions being similar to the interspecific divergence between T. wilkinsoni and its sibling species, Thaumetopoea pityocampa (Denis and Schiffermuller, 1775). Both mitochondrial and microsatellite markers showed a clear longitudinal (east-west) differentiation of populations within Crete. Our results thus suggest that T. wilkinsoni crossed the Mid-Aegean Trench, became isolated on Crete and differentiated through vicariance after the end of the Messinian Salinity Crisis, favouring the emergence of an endemic lineage. There, Quaternary climatic oscillations coupled with geographical barriers to gene flow have given rise to the currently observed east-west differentiation of Cretan populations

Patterns of expansion of pine processionary moth and its specialist egg parasitoid at the northern edge of its distributional range

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