The URGI plants and bio-agressors genomics annotation system

The URGI genomic annotation platform, developed in the framework of the GnpAnnot project, relies on well known GMOD tools (http://gmod.org): Apollo, Chado and GBrowse. Apollo is the graphical interface for visualization and annotation edition allowing curators to edit their genes according to evidences (transcript and protein similarity, comparative genomics). Manual annotations (gene curation validated/in progress) are saved in a dedicated Chado database and shared at the same time with other community annotations members. Validated genes/pseudogenes are then committed in the second Chado database accessible by GBrowse. (Résumé d'auteur

The direct protein-protein interaction results in the arms race co-evolution between Magnaporthe oryzae AVR-Pik and rice Pik

Between pathogen and host, antagonistic interactions impose strong reciprocal selection on each organism, leading to the development of arms race evolutionary dynamics. However, studies on specific recognition and co-evolution between resistance (R-) gene and avirulence (AVR-) gene are still limited. Here we show that AVRPik of Magnaporthe oryzae, the rice blast pathogen, and cognate rice R-gene Pik exhibit high levels of DNA polymorphisms causing amino acid changes. We found a tight recognition specificity of AVRPik alleles by different Pik alleles. Pik is composed of two kinds of CC-NBS-LRR, Pik1 and Pik2. We found that AVR-Pik physically interacts with the N-terminal coiled-coil domain of Pik1 in yeast 2-hybrid assay as well as in in-planta co-immunoprecipitation assay. Furthermore, this binding specificity corresponds to the recognition specificity between AVR-Pik and Pik alleles. These data suggest that the direct protein-protein interaction results in the arms race co-evolution between AVR-Pik and Pik. (Texte intégral

The plant-ant Camponotus schmitzi helps its carnivorous host-plant Nepenthes bicalcarata to catch its prey

The Bornean climber, Nepenthes bicalcarata, is unique among plants because it is both carnivorous and myrmecophytic, bearing pitcher-shaped leaves and the ant Camponotus schmitzi within tendrils. We explored, in the peat swamp forests of Brunei, the hypothesis that these ants contribute to plant nutrition by catching and digesting its prey.Wefirst tested whether ants increasedplant's capture rate.Wefound that unlikemost plant-ants, C. schmitzidonot exhibit dissuasive leaf-patrolling behaviour (zero patrol on 67 pitchers of 10 plants) but lie concealed under pitcher rim (13 ± 6 ants per pitcher) allowing numerous insect visits. However, 47 out of 50 individuals of the largest visitor dropped into the pitchers of five plants were attacked by ants and the capture rate of the same pitchers deprived of their ambush hunting ants decreased three-fold.We then tested whether ants participated in plant's digestion.We showed in a 15-d long experiment that ants fed on prey and returned it in pieces in seven out of eight pitchers. The 40 prey deposited in ant-deprived pitchers remained intact indicating a weak digestive power of the fluid confirmed to be only weakly acidic (pH ?5, n = 67). The analysis of 10 pitcher contents revealed that prey, mainly ants and termites, was very numerous (?400 per pitcher per plant) and highly fragmented. Altogether, these data suggest a positive effect of C. schmitzi on both prey intake and breakdown. This ant-plant interaction could thus be a nutritional mutualism involving the unusual association of carnivory and myrmecotrophy

honeybee workers exhibit conserved molecular responses to diverse pathogens

Background Organisms typically face infection by diverse pathogens, and hosts are thought to have developed specific responses to each type of pathogen they encounter. The advent of transcriptomics now makes it possible to test this hypothesis and compare host gene expression responses to multiple pathogens at a genome-wide scale. Here, we performed a meta-analysis of multiple published and new transcriptomes using a newly developed bioinformatics approach that filters genes based on their expression profile across datasets. Thereby, we identified common and unique molecular responses of a model host species, the honey bee (Apis mellifera), to its major pathogens and parasites: the Microsporidia Nosema apis and Nosema ceranae, RNA viruses, and the ectoparasitic mite Varroa destructor, which transmits viruses. Results We identified a common suite of genes and conserved molecular pathways that respond to all investigated pathogens, a result that suggests a commonality in response mechanisms to diverse pathogens. We found that genes differentially expressed after infection exhibit a higher evolutionary rate than non- differentially expressed genes. Using our new bioinformatics approach, we unveiled additional pathogen-specific responses of honey bees; we found that apoptosis appeared to be an important response following microsporidian infection, while genes from the immune signalling pathways, Toll and Imd, were differentially expressed after Varroa/virus infection. Finally, we applied our bioinformatics approach and generated a gene co-expression network to identify highly connected (hub) genes that may represent important mediators and regulators of anti-pathogen responses. Conclusions Our meta-analysis generated a comprehensive overview of the host metabolic and other biological processes that mediate interactions between insects and their pathogens. We identified key host genes and pathways that respond to phylogenetically diverse pathogens, representing an important source for future functional studies as well as offering new routes to identify or generate pathogen resilient honey bee stocks. The statistical and bioinformatics approaches that were developed for this study are broadly applicable to synthesize information across transcriptomic datasets. These approaches will likely have utility in addressing a variety of biological questions

Social immunity in honeybees-Density dependence, diet, and body mass trade-offs

Group living is favorable to pathogen spread due to the increased risk of disease transmission among individuals. Similar to individual immune defenses, social immunity, that is antiparasite defenses mounted for the benefit of individuals other than the actor, is predicted to be altered in social groups. The eusocial honey bee (Apis mellifera) secretes glucose oxidase (GOX), an antiseptic enzyme, throughout its colony, thereby providing immune protection to other individuals in the hive. We conducted a laboratory experiment to investigate the effects of group density on social immunity, specifically GOX activity, body mass and feeding behavior in caged honey bees. Individual honeybees caged in a low group density displayed increased GOX activity relative to those kept at a high group density. In addition, we provided evidence for a trade-off between GOX activity and body mass: Individuals caged in the low group density had a lower body mass, despite consuming more food overall. Our results provide the first experimental evidence that group density affects a social immune response in a eusocial insect. Moreover, we showed that the previously reported trade-off between immunity and body mass extends to social immunity. GOX production appears to be costly for individuals, and potentially the colony, given that low body mass is correlated with small foraging ranges in bees. At high group densities, individuals can invest less in social immunity than at low densities, while presumably gaining shared protection from infection. Thus, there is evidence that trade-offs at the individual level (GOX vs. body mass) can affect colony-level fitness

Evolution moléculaire de loci effecteurs et de gènes d'avirulence chez Magnaporthe oryzae, champignon pathogène de riz et d'autres Poacées : [P02/07]

National audienc

Impact of controlled neonicotinoid exposure on bumblebees in a realistic field setting

1. Pesticide exposure has been implicated as a contributor to insect pollinator declines. In social bees, which are crucial pollination service providers, the effect of low-level chronic exposure is typically non-lethal leading researchers to consider whether exposure induces sub-lethal effects on behaviour and whether such impairment can affect colony development. 2. Studies under laboratory conditions can control levels of pesticide exposure and elucidate causative effects, but are often criticised for being unrealistic. In contrast, field studies can monitor bee responses under a more realistic pesticide exposure landscape; yet typically such findings are limited to correlative results, and can lack true controls or sufficient replication. We attempt to bridge this gap by exposing bumblebees to known amounts of pesticides when colonies are placed in the field. 3. Using 20 bumblebee colonies, we assess the consequences of exposure to the neonicotinoid clothianidin, provided in sucrose at a concentration of five parts per billion, over five weeks. We monitored foraging patterns and pollen collecting performance from 3282 bouts using either a non-invasive photographic assessment, or by extracting the pollen from returning foragers. We also conducted a full colony census at the beginning and end of the experiment. 4. In contrast to studies on other neonicotinoids, showing clear impairment to foraging behaviours, we detected only subtle changes to patterns of foraging activity and pollen foraging during the course of the experiment. However, our colony census measures showed a more pronounced effect of exposure, with fewer adult workers and sexuals in treated colonies after five weeks. 5. Synthesis and applications. Pesticide induced impairments on colony development and foraging could impact on the pollination service that bees provide. Therefore our findings, that bees show subtle changes in foraging behaviour and reductions in colony size after exposure to a common pesticide, has important implications and helps to inform the debate over whether the benefits of systemic pesticide application to flowering crops outweigh the costs. We propose that our methodology is an important advance to previous semi-field methods and should be considered when considering improvements to current ecotoxicological guidelines for pesticide risk assessment

Providing foraging resources for solitary bees on farmland: current schemes for pollinators benefit a limited suite of species

1. Changes in agricultural practice across Europe and North America have been associated with range contractions and a decline in the abundance of wild bees. Concerns at these declines has led to the development of flower-rich agri-environment schemes as a way to enhance bee diversity and abundance. Whilst the effect of these schemes on bumblebee species (Bombus spp.) has been well studied, their impact on the wider bee community is poorly understood. 2. We used direct observations of foraging bees and pollen load analysis to quantify the relative contribution that sown flowers (i.e. those included in agri-environment scheme seed mixes) make to the pollen diets of wild solitary bees on Higher Level Stewardship farms (HLS) implementing pollinator-focused schemes and on Entry Level Stewardship farms (ELS) without such schemes in southern England, UK. 3. HLS management significantly increased floral abundance, and as the abundance of sown flowers increased these sown plants were utilised for pollen by a greater proportion of the solitary bee species present. However, the overall proportion of pollen collected from sown plants was low for both direct observations (27.0%) and pollen load analysis (23.3%). 4. At most only 25 of the 72 observed species of solitary bee (34.7%) were recorded utilising sown plants to a meaningful degree. The majority of solitary bee species did not collect pollen from flower species sown for pollinators. 5. Total bee species richness was significantly associated with plant species richness, but there was no difference in the total species richness of either bee or flowering plant species between HLS and ELS farms. 6. Synthesis and applications. These results show that the majority of solitary bee species present on farmland in the south-east of England collect the majority of their pollen from plants that persist unaided in the wider environment, not from those included in agri-environment schemes focused on pollinators. If diverse bee communities are to be maintained on farmland, existing schemes should contain an increased number of flowering plant species and additional schemes that increase the diversity of flowering plants in complementary habitats should be studied and trialled