Population genetics of the Mediterranean corn borer (Sesamia nonagrioides) differs between wild and cultivated plants.

The population genetic structure of crop pest populations gives information about their spatial ecology, which helps in designing management strategies. In this paper, we investigated the genetic structure of the Mediterranean Corn Borer (MCB), Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), one of the most important maize pests in the Mediterranean countries, using microsatellite markers for the first time in this species. Insects were collected in twenty-five locations in southwest and southeast France from cultivated and wild host plants (Zea mays, Sorghum halepense and Typha domingensis). Contrary to what has been reported so far in France, we found that MCB populations could be locally abundant on wild poales plants. Analysis was carried out at 11 polymorphic microsatellite markers. Molecular variance was significantly determined by geography, then by host plant, with 17% and 4%, respectively, when considered as a major effect, and with 14% and 1%, respectively, when considered as a marginal effect in permutational analysis. Multidimensional scaling (MDS) and GENELAND Bayesian clustering suggested that populations infecting wild plants (T. domingensis and S. halepense) were more structured locally than those affecting cultivated maize. In S. halepense, significant Isolation By Distance (IBD) indicated that this factor could explain genetic differentiation of the moth populations. In T. domingensis, local population differentiation was strong but did not depend on distance. The implication of this absence of population structure in maize and the heterogeneity of population genetics patterns in wild plants are discussed in the context of the population dynamics hypothesis and population management strategies.

Relationship between oviposition, virulence gene expression and parasitism success in Cotesia typhae nov. sp. parasitoid strains.

Studying mechanisms that drive host adaptation in parasitoids is crucial for the efficient use of parasitoids in biocontrol programs. Cotesia typhae nov. sp. (Fernández-Triana) (Hymenoptera: Braconidae) is a newly described parasitoid of the Mediterranean corn borer Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae). Braconidae are known for their domesticated bracovirus, which is injected with eggs in the host larva to overcome its resistance. In this context, we compared reproductive success traits of four Kenyan strains of C. typhae on a French and a Kenyan populations of its host. Differences were found between the four strains and the two most contrasted ones were studied more thoroughly on the French host population. Parasitoid offspring size was correlated with parasitism success and the expression of bracovirus virulence genes (CrV1 and Cystatin) in the host larva after parasitism. Hybrids between these two parasitoid strains showed phenotype and gene expression profiles similar to the most successful parental strain, suggesting the involvement of dominant alleles in the reproductive traits. Ovary dissections revealed that the most successful strain injected more eggs in a single host larva than the less successful one, despite an equal initial ovocyte number in ovaries. It can be expected that the amount of viral particles increase with the number of eggs injected. The ability to bypass the resistance of the allopatric host may in consequence be related to the oviposition behaviour (eggs allocation). The influence of the number of injected eggs on parasitism success and on virulence gene expression was evaluated by oviposition interruption experiments.

The Cotesia sesamiae story: insight into host-range evolution in a Hymenoptera parasitoid and implication for its use in biological control programs.

This review covers nearly 20 years of studies on the ecology, physiology and genetics of the Hymenoptera Cotesia sesamiae, an African parasitoid of Lepidoptera that reduces populations of common maize borers in East and South Africa. The first part of the review presents studies based on sampling of C. sesamiae from maize crops in Kenya. From this agrosystem including one host plant and three main host borer species, studies revealed two genetically differentiated populations of C. sesamiae species adapted to their local host community, and showed that their differentiation involved the joint evolution of virulence genes and sensory mechanisms of host acceptance, reinforced by reproductive incompatibility due to Wolbachia infection status and natural inbreeding. In the second part, we consider the larger ecosystem of wild Poales plant species hosting many Lepidoptera stem borer species that are potential hosts for C. sesamiae. The hypothesis of other host-adapted C. sesamiae populations was investigated based on a large sampling of stem borer larvae on various Poales across sub-Saharan Africa. The sampling provided information on the respective contribution of local hosts, biogeography and Wolbachia in the genetic structure of C. sesamiae populations. Molecular evolution analyses highlighted that several bracovirus genes were under positive selection, some of them being under different selection pressure in C. sesamiae populations adapted to different hosts. This suggests that C. sesamiae host races result from co-evolution acting at the local scale on different bracovirus genes. The third part considers the mechanisms driving specialization. C. sesamiae host races are more or less host-specialized. This character is crucial for efficient and environmentally-safe use of natural enemies for biological control of pests. One method to get an insight in the evolutionary stability of host-parasite associations is to characterize the phylogenetic relationships between the so-called host-races. Based on the construction of a phylogeny of C. sesamiae samples from various host- and plant species, we revealed three main lineages. Mechanisms of differentiation are discussed with regard to the geography and ecology of the samples. One of the lineage presented all the hallmarks of a distinct species, which has been morphologically described and is now studied in the perspective of being used as biological control agent against Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), a major maize pest in West Africa and Mediterranean countries (see Benoist et al. 2017). The fourth part reviews past and present use of C. sesamiae in biological control, and points out the interest of such molecular ecology studies to reconcile biodiversity and food security stakes in future biological control.

Fontes de contaminação de Yersinia enterocolitica durante a produção de leite / Contamination sources of Yersinia enterocolitica during milk production

Objetivou-se determinar as possíveis fontes de contaminação de Yersinia enterocolitica em diferentes pontos do processo de ordenha de vacas leiteiras em oito propriedades da região de Pelotas, RS, ao longo de um ano. Foram analisadas amostras de leite cru de conjunto logo após a ordenha, água de estábulo leiteiro, mão de ordenhador, balde de recolhimento do leite e insuflador de teteiras. As amostras de leite cru e água foram coletadas em frascos estéreis, e as amostras de mão, balde e teteiras com zaragatoas estéreis. As amostras de leite cru foram submetidas a um pré-enriquecimento em água peptonada, sendo posteriormente incubadas em caldo PSTA, adicionado de ampicilina. As amostras de água foram filtradas em membrana de éster de celulose e incubadas em caldo TSB. As amostras de leite após incubação em PSTA, as membranas utilizadas na filtragem da água incubadas em TSB, bem como o material de mãos, balde e teteiras coletadas nas zaragatoas, foram semeados em ágar MacConkey e incubados para a obtenção de colônias. Colônias características foram analisadas por meio de duplex PCR para confirmação da espécie. Os perfis moleculares dos isolados de Y. enterocolitica foram comparados utilizando-se a técnica de rep-PCR. Y. enterocolitica foi isolada de 9,37% das amostras de leite, 6,25% das amostras de água e 12,5% das amostras de mão. Não houve similaridade no perfil de bandas dos isolados encontrados, entretanto foi identificada a presença de cepas diferentes na mesma amostra, demonstrando uma variedade grande de cepas distribuídas no ambiente. A presença de Y. enterocolitica em leite cru no Brasil é preocupante, já que uma quantidade considerável do produto ainda é comercializada de forma clandestina, expondo o consumidor ao risco de infecção pela bactéria, ao consumi-lo sem tratamento térmico adequado.(AU)

This work was performed in order to determine the possible Yersinia enterocolitica contamination sources at different points of the dairy cows milking process in eight properties of Pelotas, RS, in a year. Raw milk samples were analyzed immediately after milking, as well as water from milking parlor, milkers' hands, milk collection bucket, and inflator liners. The samples of raw milk and water were collected in sterile bottles and hand samples, and sterile swabs were used for the buckets and liners. The raw milk samples were subjected to a pre-enrichment peptone water buffered and subsequently incubated in PSTA broth with added ampicillin. Water samples were filtered through cellulose ester membrane and incubated in TSB medium. The milk samples after incubation in PSTA, the membranes used in water filtration were incubated in TSB and the material of the hands material, bucket and liners collected in the swabs were plated on MacConkey agar to obtain colonies. Characteristics of colonies were analyzed by duplex PCR to confirm the species. The molecular profiles of Y. enterocolitica isolates were compared using rep-PCR. Y. enterocolitica was isolated from 9,37% of milk samples, 6,25% of water samples and 12,5% of hand samples. There weren't similarities in the band profile of the isolates found; however, the presence of different strains was found in the same sample, demonstrating a variety of strains distributed in the environment. The presence of Y. enterocolitica in raw milk in Brazil is dangerous, considering that the product is sold clandestinely, exposing consumers to the risk of infection by the bacterium, when consuming it without proper heat treatment.(AU)

Genetic hitchhiking and resistance evolution to transgenic Bt toxins: insights from the African stalk borer Busseola fusca (Noctuidae).

Since transgenic crops expressing Bacillus thuringiensis (Bt) toxins were first released, resistance evolution leading to failure in control of pests populations has been observed in a number of species. Field resistance of the moth Busseola fusca was acknowledged 8 years after Bt maize was introduced in South Africa. Since then, field resistance of this corn borer has been observed at several locations, raising questions about the nature, distribution and dynamics of the resistance trait. Using genetic markers, our study identified four outlier loci clearly associated with resistance. In addition, genetic structure at neutral loci reflected extensive gene flow among populations. A realistically parameterised model suggests that resistance could travel in space at speed of several kilometres a year. Markers at outlier loci delineated a geographic region associated with resistance spread. This was an area of approximately 100 km radius, including the location where resistance was first reported. Controlled crosses corroborated these findings and showed significant differences of progeny survival on Bt plants depending on the origin of the resistant parent. Last, our study suggests diverse resistance mutations, which would explain the widespread occurrence of resistant larvae in Bt fields across the main area of maize production in South Africa.

Permanent genetic resources added to Molecular Ecology Resources Database 1 August 2011-30 September 2011.

This article documents the addition of 299 microsatellite marker loci and nine pairs of single-nucleotide polymorphism (SNP) EPIC primers to the Molecular Ecology Resources (MER) Database. Loci were developed for the following species: Alosa pseudoharengus, Alosa aestivalis, Aphis spiraecola, Argopecten purpuratus, Coreoleuciscus splendidus, Garra gotyla, Hippodamia convergens, Linnaea borealis, Menippe mercenaria, Menippe adina, Parus major, Pinus densiflora, Portunus trituberculatus, Procontarinia mangiferae, Rhynchophorus ferrugineus, Schizothorax richardsonii, Scophthalmus rhombus, Tetraponera aethiops, Thaumetopoea pityocampa, Tuta absoluta and Ugni molinae. These loci were cross-tested on the following species: Barilius bendelisis, Chiromantes haematocheir, Eriocheir sinensis, Eucalyptus camaldulensis, Eucalyptus cladocalix, Eucalyptus globulus, Garra litaninsis vishwanath, Garra para lissorhynchus, Guindilla trinervis, Hemigrapsus sanguineus, Luma chequen. Guayaba, Myrceugenia colchagüensis, Myrceugenia correifolia, Myrceugenia exsucca, Parasesarma plicatum, Parus major, Portunus pelagicus, Psidium guayaba, Schizothorax richardsonii, Scophthalmus maximus, Tetraponera latifrons, Thaumetopoea bonjeani, Thaumetopoea ispartensis, Thaumetopoea libanotica, Thaumetopoea pinivora, Thaumetopoea pityocampa ena clade, Thaumetopoea solitaria, Thaumetopoea wilkinsoni and Tor putitora. This article also documents the addition of nine EPIC primer pairs for Euphaea decorata, Euphaea formosa, Euphaea ornata and Euphaea yayeyamana.

Specific mesenchymal/epithelial induction of olfactory receptor, vomeronasal, and gonadotropin-releasing hormone (GnRH) neurons.

We asked whether specific mesenchymal/epithelial (M/E) induction generates olfactory receptor neurons (ORNs), vomeronasal neurons (VRNs), and gonadotropin-releasing hormone (GnRH) neurons, the major neuron classes associated with the olfactory epithelium (OE). To assess specificity of M/E-mediated neurogenesis, we compared the influence of frontonasal mesenchyme on frontonasal epithelium, which becomes the OE, with that of the forelimb bud. Despite differences in position, morphogenetic and cytogenic capacity, both mesenchymal tissues support neurogenesis, expression of several signaling molecules and neurogenic transcription factors in the frontonasal epithelium. Only frontonasal mesenchyme, however, supports OE-specific patterning and activity of a subset of signals and factors associated with OE differentiation. Moreover, only appropriate pairing of frontonasal epithelial and mesenchymal partners yields ORNs, VRNs, and GnRH neurons. Accordingly, the position and molecular identity of specialized frontonasal epithelia and mesenchyme early in gestation and subsequent inductive interactions specify the genesis and differentiation of peripheral chemosensory and neuroendocrine neurons.

In vivo vomeronasal stimulation reveals sensory encoding of conspecific and allospecific cues by the mouse accessory olfactory bulb.

The rodent vomeronasal system plays a critical role in mediating pheromone-evoked social and sexual behaviors. Recent studies of the anatomical and molecular architecture of the vomeronasal organ (VNO) and of its synaptic target, the accessory olfactory bulb (AOB), have suggested that unique features underlie vomeronasal sensory processing. However, the neuronal representation of pheromonal information leading to specific behavioral and endocrine responses has remained largely unexplored due to the experimental difficulty of precise stimulus delivery to the VNO. To determine the basic rules of information processing in the vomeronasal system, we developed a unique preparation that allows controlled and repeated stimulus delivery to the VNO and combined this approach with multisite recordings of neuronal activity in the AOB. We found that urine, a well-characterized pheromone source in mammals, as well as saliva, activates AOB neurons in a manner that reliably encodes the donor animal's sexual and genetic status. We also identified a significant fraction of AOB neurons that respond robustly and selectively to predator cues, suggesting an expanded role for the vomeronasal system in both conspecific and interspecific recognition. Further analysis reveals that mixed stimuli from distinct sources evoke synergistic responses in AOB neurons, thereby supporting the notion of integrative processing of chemosensory information.

Isolation and characterization of polymorphic microsatellites in the Potato Tuber Moth Tecia solanivora (Povolny, 1973) (Lepidoptera: Gelechiidae).

Nine polymorphic microsatellite markers were isolated from Tecia solanivora, one of the most serious pests of potato tubers in Central and South America. As found in other studies of Lepidoptera, development of microsatellites is a difficult task: in our case, despite the large number of clones sequenced (796), of which 70 were unique, only nine loci were found to be both variable, and in Hardy-Weinberg equilibrium, No null alleles were detected. The loci were tested in three other co-occurring Gelechiidae species, one of which was variable. These loci will be used to provide a greater understanding of the genetic changes occurring during the invasive process in this species.

Genetic analysis of brain circuits underlying pheromone signaling.

Molecular approaches and genetic manipulations have provided novel insights into the processing of pheromone-mediated information by the olfactory and vomeronasal systems of mammals. We will review and discuss the specific contribution of each of the two chemosensory systems that ensure specific behavioral responses to conspecific animals.

Profiling brain transcription: neurons learn a lesson from yeast.

The application of microarray technologies to the brain poses unique challenges, because of the complexity of the central nervous system and the availability of resources. Nevertheless, recent studies using DNA chips have made inroads into the molecular characterization of regional and functional brain units, the identification of developmental gene expression patterns, and the discovery of transcriptional differences associated with behavioral and neuropathological traits.

Sensory coding of pheromone signals in mammals.

The vomeronasal organ (VNO) of mammals plays an essential role in the detection of pheromones, chemical cues secreted by animals that elicit genetically programmed sexual and aggressive behaviors among conspecifics. The recent characterization of genes encoding molecular components of the VNO sensory response suggests that VNO neurons express a unique set of molecules to recognize and translate pheromone signals into neuronal electrical activity. Identification of these genes, which include putative pheromone receptor genes, has offered a new opportunity to uncover basic principles of pheromone sensory processing and important aspects of vomeronasal development.

Responses of vomeronasal neurons to natural stimuli.

The vomeronasal organ (VNO) of mammals plays an essential role in the detection of pheromones. We obtained simultaneous recordings of action potentials from large subsets of VNO neurons. These cells responded to components of urine by increasing their firing rate. This chemosensory activation required phospholipase C function. Unlike most other sensory neurons, VNO neurons did not adapt under prolonged stimulus exposure. The full time course of the VNO spiking response is captured by a simple quantitative model of ligand binding. Many individual VNO neurons were strongly selective for either male or female mouse urine, with the effective concentrations differing as much as a thousandfold. These results establish a framework for understanding sensory coding in the vomeronasal system.

A novel family of candidate pheromone receptors in mammals.

Pheromonal activation of the vomeronasal organ (VNO) elicits genetically preprogrammed behaviors and physiological changes in mammals. We have identified a novel gene family encoding over one hundred VNO specific receptors, the V3Rs. V3R sequences are highly similar to each other and appear distantly related to the putative pheromone receptors, V1Rs, and the taste receptors, T2Rs. Within the VNO, V3R-positive neurons are distinct from neurons expressing the pheromone receptor families V1R and V2R. The V3Rs are likely to represent a new large family of pheromone receptors in mammals. Multiple V3R-related human sequences have been identified, including one clone retaining the capacity to create a complete and functional transcript. Our data uncover a striking complexity in the molecular and cellular organization of the VNO and provide an essential framework for the study of pheromone signaling in mammals.

TRP2: a candidate transduction channel for mammalian pheromone sensory signaling.

The vomeronasal organ (VNO) of terrestrial vertebrates plays a key role in the detection of pheromones, chemicals released by animals that elicit stereotyped sexual and aggressive behaviors among conspecifics. Sensory transduction in the VNO appears unrelated to that in the vertebrate olfactory and visual systems: the putative pheromone receptors of the VNO are evolutionarily independent from the odorant receptors and, in contrast to vertebrate visual and olfactory transduction, vomeronasal transduction is unlikely to be mediated by cyclic-nucleotide-gated channels. We hypothesized that sensory transduction in the VNO might instead involve an ion channel of the transient receptor potential (TRP) family, members of which mediate cyclic-nucleotide-independent sensory responses in Drosophila melanogaster and Caenorhabditis elegans and play unknown functions in mammals. We have isolated a cDNA (rTRP2) from rat VNO encoding a protein of 885 amino acids that is equally distant from vertebrate and invertebrate TRP channels (10-30% amino acid identity). rTRP2 mRNA is exclusively expressed in VNO neurons, and the protein is highly localized to VNO sensory microvilli, the proposed site of pheromone sensory transduction. The absence of Ca2+ stores in sensory microvilli suggests that, in contrast to a proposed mechanism of activation of mammalian TRP channels, but in accord with analysis of TRP function in Drosophila phototransduction, the gating of TRP2 is independent from the depletion of internal Ca2+ stores. Thus, TRP2 is likely to participate in vomeronasal sensory transduction, which may share additional similarities with light-induced signaling in the Drosophila eye.

A map of pheromone receptor activation in the mammalian brain.

In mammals, the detection of pheromones is mediated by the vomeronasal system. We have employed gene targeting to visualize the pattern of projections of axons from vomeronasal sensory neurons in the accessory olfactory bulb. Neurons expressing a specific receptor project to multiple glomeruli that reside within spatially restricted domains. The formation of this sensory map in the accessory olfactory bulb and the survival of vomeronasal organ sensory neurons require the expression of pheromone receptors. In addition, we observe individual glomeruli in the accessory olfactory bulb that receive input from more than one type of sensory neuron. These observations indicate that the organization of the vomeronasal sensory afferents is dramatically different from that of the main olfactory system, and these differences have important implications for the logic of olfactory coding in the vomeronasal organ.

Molecular identity of hematopoietic precursor cells emerging in the human embryo.

It is now accepted from studies in animal models that hematopoietic stem cells emerge in the para-aortic mesoderm-derived aorta-gonad-mesonephros region of the vertebrate embryo. We have previously identified the equivalent primitive hematogenous territory in the 4- to 6-week human embryo, under the form of CD34(+)CD45(+)Lin- high proliferative potential hematopoietic cells clustered on the ventral endothelium of the aorta. To characterize molecules involved in initial stem cell emergence, we first investigated the expression in that territory of known early hematopoietic regulators. We herein show that aorta-associated CD34(+) cells coexpress the tal-1/SCL, c-myb, GATA-2, GATA-3, c-kit, and flk-1/KDR genes, as do embryonic and fetal hematopoietic progenitors later present in the liver and bone marrow. Next, CD34(+)CD45(+) aorta-associated cells were sorted by flow cytometry from a 5-week embryo and a cDNA library was constructed therefrom. Differential screening of that library with total cDNA probes obtained from CD34(+) embryonic liver cells allowed the isolation of a kinase-related sequence previously identified in KG-1 cells. In addition to emerging blood stem cells, KG-1 kinase is also strikingly expressed in all developing endothelial cells in the yolk sac and embryo, which suggests its involvement in the genesis of both hematopoietic and vascular cell lineages in humans.