Burial and seed survival in Brassica napus subsp. oleifera and Sinapis arvensis including a comparison of transgenic and non-transgenic lines of the crop

The creation of transgenic plants through genetic engineering has focused interest on how the fitness of a plant species may be altered by small changes in its genome. This study concentrates on a key component of fitness: persistence of seeds overwinter. Seeds of three lines of oilseed rape (Brassica napus subsp. oleifera DC Metzger) and of charlock (Sinapis arvensis L.) were buried in nylon mesh bags at two depths in four habitats in each of three geographically separated sites: Cornwall, Berkshire and Sutherland. Seeds were recovered after 12 and 24 months. Charlock exhibited much greater seed survival (average 60 per cent surviving the first year and 32.5 per cent surviving the second year) than oilseed rape (1.5 per cent surviving the first year and 0.2 per cent surviving the second) at all sites. Charlock showed higher survival at 15 cm burial than 2 cm burial at certain sites, but oilseed rape showed no depth effect. Different genetic lines of oilseed rape displayed different rates of seed survival; non-transgenic rape showed greater survival (2 per cent) than the two transgenic lines, one developed for tolerance to the antibiotic kanamycin (0.3 per cent) and one for tolerance to both kanamycin and the herbicide glufosinate (0.25 per cent). The absolute and relative performances of the different genetic lines of oilseed rape were context specific, illustrating the need to test hypotheses in a wide range of ecological settings

Sick wings: the effects of the baculovirus AcMNPV on wing development in the speckled wood butterfly, Pararge aegeria

Baculoviruses not only affect resource allocation to growth and reproduction, but they also have the possibility to act on host signalling pathways involved in cell differentiation and thus tissue patterning. Infection typically starts in the insect gut after ingesting virally contaminated food, and the infection will spread to other tissues aided by, for example, metalloproteases. Metalloproteases, such as tolloid, regulate in normal host development the activity of the decapentaplegic (dpp) antagonist short gastrulation (sog). Dpp plays a key role in regulating wing shape, size and wing vein positioning. Overexpression of tolloid in Drosophila pupae results in wing abnormalities, especially in the posterior part of the wing, as it disturbs the balance between sog and dpp levels. It is known in Drosophila that bacteria that produce a number of different metalloproteases in their host, cause similar wing defects as when tolloid is overexpressed. The baculovirus AcMNPV produces the metalloprotease cathepsin (Ac-)v-cath. Cathepsin is not homologous to tolloid, but just as efficient a metalloprotease, and is known in flies to affect wing and leg imaginal discs outgrowth. Nothing is known, however, about how it affects wing shape and wing venation patterning. In this talk I will discuss in detail, at the phenotypic level, how wing development was affected in a series of experiments in which second instar speckled wood (Pararge aegeria) caterpillars were infected with different doses of AcMNPV. The implications of the effects of baculoviruses modulating wing development in natural populations will be discussed

Persistence and coexistence of engineered baculoviruses

Baculoviruses, and in particular, the nucleopolyhedroviruses infect a wide range of arthropod hosts and have the potential to be used as biopesticides. However, one of the major drawbacks with these pathogens as biocontrol agents is that they have a slow response time. Alterations to the speed of kill and pathogen life history characteristics can influence the competitive outcome and persistence between wildtype and modified strains. Here, we explore, theoretically, how life-history modifications of pathogens can affect the epidemiology and ecology of strain coexistence. In particular, we show how under simple mass action disease transmission, life-history difference between strains are insufficient to allow coexistence. Additional heterogeneities in transmission are shown to be necessary to facilitate coexistence of wildtype and modified pathogen strains. We also illustrate how the patterns of infectivity of wildtype and modified strains can also affect long-term coexistence, and argue that appropriate assessment of genetic modifications must be presented in terms of relevant ecological theory

Challenges in modelling complexity of fungal entomopathogens in semi-natural populations of insects

The use of fungal entomopathogens as microbial control agents has driven studies into their ecology in crop ecosystems. Yet, there is still a lack of understanding of the ecology of these insect pathogens in semi-natural habitats and communities. We review the literature on prevalence of fungal entomopathogens in insect populations and highlight the difficulties in making such measurements. We then describe the theoretical host-pathogen models available to examine the role that fungal entomopathogens could play in regulating insect populations in semi-natural habitats, much of the inspiration for which has been drawn from managed systems, particularly forests. We further emphasise the need to consider the complexity, and particularly the heterogeneity, of semi-natural habitats within the context of theoretical models and as a framework for empirical studies. We acknowledge that fundamental gaps in understanding fungal entomopathogens from an ecological perspective coupled with a lack of empirical data to test theoretical predictions is impeding progress. There is an increasing need, especially under current rapid environmental change, to improve our understanding of the role of fungi in insect population dynamics beyond the context of forestry and agriculture

Microparasite manipulation of an insect: the influence of the egt gene on the interaction between a baculovirus and its lepidopteran host

Parasites and pathogens manipulate their hosts in a variety of ways that are thought to enhance their fitness. However, it is rare to be able to link such phenotypic changes to specific genes. 2. Here the effect of a single pathogen gene is examined. The ecdysteroid UDP-glucosyltransferase (egt) gene of insect baculoviruses produces an enzyme that interferes with host moulting. 3. The effect of the egt gene was examined by comparing two baculoviruses that differed only in the expression of this gene. All three fitness traits examined ¿ pathogenicity, infection duration and pathogen productivity ¿ were affected by deletion of the gene. 4. Trichoplusia ni larvae in all five instars died earlier when infected with the egt-minus virus compared with those infected by the wild-type Autographa californica nucleopolyhedrovirus. 5. Unexpectedly, the egt-minus virus was more pathogenic to final instar larvae than the wild-type virus. Virus genotype and dose both influenced insect development. 6. Wild-type infected insects had a significantly higher yield of virus at death, cadaver weight and yield of virus per unit weight than those infected with the egt-minus virus. 7. The size of the virus challenge had a major influence on the outcome of the interaction. The consequences of these data for pathogen fitness are discussed

Considerations in environmental science and management for the design of natural asset checks in public policy appraisal

In 2010, the Government Economic Service Review of the Economics of Sustainable Development recommended that a natural asset check should be investigated for use in the appraisal of public policy options. Considerations in environmental science and management can help to ensure that issues such as the ecological thresholds, cumulative impacts, the selection of appropriate accounting units and risk are handled appropriately in any natural asset check. Based on assessment of the contribution of the UK National Ecosystem Assessment (UK NEA) and other work, this paper makes a series of propositions in relation to the design of a natural asset check: 1. While the UK NEA draws together much of the information needed to design a natural asset check, a development of this framework will be required in order to perform the check. 2. Some kind of accounting model is likely to be more useful as a basis for a natural asset check than the frameworks used for ecosystem assessments. 3. A classification approach that links ecosystem services to the natural assets that underpin them is probably more efficient in capturing what is important in policy terms, than one that is based on a more abstract and generic classification of assets. 4. There are sufficient data resources available for a preliminary audit of natural assets to be made. 5. While a focus on non-marginal or irreversible changes in natural systems is important, it would be too restrictive to make this the exclusive concern of any natural asset check. 6. What might be considered critical natural assets may change as knowledge develops or circumstances change. Therefore, a ‘one-off’ natural asset check is unlikely to be reliable for policy analysis in the long term. Periodic audit will be necessary

Manipulation of host cytokine network by ticks: a potential gateway for pathogen transmission

Ticks are obligatory blood-feeding arthropods that secrete various immunomodulatory molecules to antagonize host inflammatory and immune responses. Cytokines play an important role in regulating these responses. We investigated the extent to which ticks interact with the sophisticated cytokine network by comparing the effect of salivary gland extracts (SGE) of 3 ixodid tick species, Dermacentor reticulatus, Amblyomma variegatum and Ixodes ricinus, all of which are important vectors of tick-borne pathogens. Using specific ELISAs, anti-cytokine activity was demonstrated with 7 cytokines: IL-8, MCP-1, MIP-1α, RANTES, eotaxin, IL-2 and IL-4. The results varied between species, and between adult males and females of the same species. Relatively high activity levels were detected in saliva of female D. reticulatus, confirming that the observed anti-cytokine activities are an integral part of tick saliva secreted into the host. Results with fractionated SGE indicated that from 2 to 6 putative cytokine binding molecules are produced, depending on species and sex. Binding ability of SGE molecules was verified by cross-linking with radio-isotope labelled MIP-1α. By targeting different cytokines, ixodid ticks can manipulate the cytokine network, which will greatly facilitate blood-feeding and provide a gateway for tick-borne pathogens that helps explain why ticks are such efficient and effective disease vectors