Interplay of robustness and plasticity of life history traits in habitats with different thermal regimes
Liefting, M. ; Grunsven, R.H.A. van; Morrissey, M.B.M. ; Timmermans, M. ; Ellers, J. - \ 2015
Journal of Evolutionary Biology 28 (2015)5. - ISSN 1010-061X - p. 1057 - 1066.
orchesella-cincta collembola - wild bird population - phenotypic plasticity - reaction norms - genetic-structure - environmental canalization - drosophila-melanogaster - indeterminate growth - soil arthropod - evolution
Phenotypic plasticity describes the ability of an individual to alter its phenotype in response to the environment and is potentially adaptive when dealing with environmental variation. However, robustness in the face of a changing environment may often be beneficial for traits that are tightly linked to fitness. We hypothesized that robustness of some traits may depend on specific patterns of plasticity within and among other traits. We used a reaction norm approach to study robustness and phenotypic plasticity of three life-history traits of the collembolan Orchesella cincta in environments with different thermal regimes. We measured adult mass, age at maturity and growth rate of males and females from heath and forest habitats at two temperatures (12 and 22 °C). We found evidence for ecotype-specific robustness of female adult mass to temperature, with a higher level of robustness in the heath ecotype. This robustness is facilitated by plastic adjustments of growth rate and age at maturity. Furthermore, female fecundity is strongly influenced by female adult mass, explaining the importance of realizing a high mass across temperatures for females. These findings indicate that different predicted outcomes of life-history theory can be combined within one species' ontogeny and that models describing life-history strategies should not assume that traits like growth rate are maximized under all conditions. On a methodological note, we report a systematic inflation of variation when standard deviations and correlation coefficients are calculated from family means as opposed to individual data within a family structure.
We can't all be supermodels: the value of comparative transcriptomics to the study of non-model insects
Oppenheim, S.J. ; Baker, R.H. ; Simon, S. ; DeSalle, R. - \ 2015
Insect Molecular Biology 24 (2015)2. - ISSN 0962-1075 - p. 139 - 154.
biased gene-expression - chromosome dosage compensation - seminal fluid proteins - asian tiger mosquito - division-of-labor - rna-seq - anopheles-gambiae - x-chromosome - honey-bees - drosophila-melanogaster
Insects are the most diverse group of organisms on the planet. Variation in gene expression lies at the heart of this biodiversity and recent advances in sequencing technology have spawned a revolution in researchers' ability to survey tissue-specific transcriptional complexity across a wide range of insect taxa. Increasingly, studies are using a comparative approach (across species, sexes and life stages) that examines the transcriptional basis of phenotypic diversity within an evolutionary context. In the present review, we summarize much of this research, focusing in particular on three critical aspects of insect biology: morphological development and plasticity; physiological response to the environment; and sexual dimorphism. A common feature that is emerging from these investigations concerns the dynamic nature of transcriptome evolution as indicated by rapid changes in the overall pattern of gene expression, the differential expression of numerous genes with unknown function, and the incorporation of novel, lineage-specific genes into the transcriptional profile.
Target of rapamycin signalling mediates the lifespan-extending effects of dietary restriction by essential amino acid alteration
Emran, S. ; Yang, M.Y. ; He, X.L. ; Zandveld, J. ; Piper, M.D.W. - \ 2014
Aging-US 6 (2014)5. - ISSN 1945-4589 - p. 390 - 398.
caenorhabditis-elegans - drosophila-melanogaster - longevity assurance - stress resistance - food restriction - fat storage - tor - extension - growth - yeast
Dietary restriction (DR), defined as a moderate reduction in food intake short of malnutrition, has been shown to extend healthy lifespan in a diverse range of organisms, from yeast to primates. Reduced signalling through the insulin/IGF-like (IIS) and Target of Rapamycin (TOR) signalling pathways also extend lifespan. In Drosophila melanogaster the lifespan benefits of DR can be reproduced by modulating only the essential amino acids in yeast based food. Here, we show that pharmacological downregulation of TOR signalling, but not reduced IIS, modulates the lifespan response to DR by amino acid alteration. Of the physiological responses flies exhibit upon DR, only increased body fat and decreased heat stress resistance phenotypes correlated with longevity via reduced TOR signalling. These data indicate that lowered dietary amino acids promote longevity via TOR, not by enhanced resistance to molecular damage, but through modified physiological conditions that favour fat accumulation.
Conserved histidine of metal transporter AtNRAMP1 is crucial for optimal plant growth under manganese deficiency at chilling temperatures
Ihnatowicz, A. ; Siwinska, J. ; Meharg, A.A. ; Carey, M. ; Koornneef, M. ; Reymond, M. - \ 2014
New Phytologist 202 (2014)4. - ISSN 0028-646X - p. 1173 - 1183.
yeast saccharomyces-cerevisiae - barley hordeum-vulgare - arabidopsis-thaliana - drosophila-melanogaster - iron transport - ion transporters - diploid strains - calcareous soil - nramp family - environment
Manganese (Mn) is an essential nutrient required for plant growth, in particular in the process of photosynthesis. Plant performance is influenced by various environmental stresses including contrasting temperatures, light or nutrient deficiencies. The molecular responses of plants exposed to such stress factors in combination are largely unknown. Screening of 108 Arabidopsis thaliana (Arabidopsis) accessions for reduced photosynthetic performance at chilling temperatures was performed and one accession (Hog) was isolated. Using genetic and molecular approaches, the molecular basis of this particular response to temperature (GxE interaction) was identified. Hog showed an induction of a severe leaf chlorosis and impaired growth after transfer to lower temperatures. We demonstrated that this response was dependent on the nutrient content of the soil. Genetic mapping and complementation identified NRAMP1 as the causal gene. Chlorotic phenotype was associated with a histidine to tyrosine (H239Y) substitution in the allele of Hog NRAMP1. This led to lethality when Hog seedlings were directly grown at 4 degrees C. Chemical complementation and hydroponic culture experiments showed that Mn deficiency was the major cause of this GxE interaction. For the first time, the NRAMP-specific highly conserved histidine was shown to be crucial for plant performance.
Ecdysteroid hormones link the juvenile environment to alternative adult life histories in a seasonal insect
Oostra, V. ; Mateus, A.R.A. ; Burg, K.R.L. van den; Piessens, T. ; Eijk, M. van; Brakefield, P.M. ; Beldade, P. ; Zwaan, B.J. - \ 2014
American Naturalist 184 (2014)3. - ISSN 0003-0147 - p. E79 - E92.
butterfly bicyclus-anynana - drosophila-melanogaster - phenotypic plasticity - developmental temperature - adaptive responses - thermal plasticity - wing pattern - lepidoptera - diapause - nymphalidae
The conditional expression of alternative life strategies is a widespread feature of animal life and a pivotal adaptation to life in seasonal environments. To optimally match suites of traits to seasonally changing ecological opportunities, animals living in seasonal environments need mechanisms linking information on environmental quality to resource allocation decisions. The butterfly Bicyclus anynana expresses alternative adult life histories in the alternating wet and dry seasons of its habitat as endpoints of divergent developmental pathways triggered by seasonal variation in preadult temperature. Pupal ecdysteroid hormone titers are correlated with the seasonal environment, but whether they play a functional role in coordinating the coupling of adult traits in the alternative life histories is unknown. Here, we show that manipulating pupal ecdysteroid levels is sufficient to mimic in direction and magnitude the shifts in adult reproductive resource allocation normally induced by seasonal temperature. Crucially, this allocation shift is accompanied by changes in ecologically relevant traits, including timing of reproduction, life span, and starvation resistance. Together, our results support a functional role for ecdysteroids during development in mediating strategic reproductive investment decisions in response to predictive indicators of environmental quality. This study provides a physiological mechanism for adaptive developmental plasticity, allowing organisms to cope with variable environments
The plastic fly: the effect of sustained fluctuations in adult food supply on life-history traits
Heuvel, J. van den; Zandveld, J. ; Mulder, M. ; Brakefield, P.M. ; Kirkwood, T.B.L. ; Shanley, D.P. ; Zwaan, B.J. - \ 2014
Journal of Evolutionary Biology 27 (2014)11. - ISSN 1010-061X - p. 2322 - 2333.
drosophila-melanogaster - phenotypic plasticity - metabolic-rate - evolution - span - reproduction - population - restriction - temperature - senescence
Many adult traits in Drosophila melanogaster show phenotypic plasticity, and the effects of diet on traits such as lifespan and reproduction are well explored. Although plasticity in response to food is still present in older flies, it is unknown how sustained environmental variation affects life-history traits. Here, we explore how such life-long fluctuations of food supply affect weight and survival in groups of flies and affect weight, survival and reproduction in individual flies. In both experiments, we kept adults on constant high or low food and compared these to flies that experienced fluctuations of food either once or twice a week. For these ‘yoyo’ groups, the initial food level and the duration of the dietary variation differed during adulthood, creating four ‘yoyo’ fly groups. In groups of flies, survival and weight were affected by adult food. However, for individuals, survival and reproduction, but not weight, were affected by adult food, indicating that single and group housing of female flies affects life-history trajectories. Remarkably, both the manner and extent to which life-history traits varied in relation to food depended on whether flies initially experienced high or low food after eclosion. We therefore conclude that the expression of life-history traits in adult life is affected not only by adult plasticity, but also by early adult life experiences. This is an important but often overlooked factor in studies of life-history evolution and may explain variation in life-history experiments
Genetics of decayed sexual traits in a parasitoid wasp with endosymbiont-induced asexuality
Ma, W.J. ; Pannebakker, B.A. ; Beukeboom, L.W. ; Schwander, T. ; Zande, L. van de - \ 2014
Heredity 113 (2014). - ISSN 0018-067X - p. 424 - 431.
wolbachia-induced parthenogenesis - leptopilina-clavipes hymenoptera - local mate competition - asobara-japonica - drosophila-melanogaster - muscidifurax-uniraptor - antibiotic-treatment - telenomus-nawai - reproduction - populations
Trait decay may occur when selective pressures shift, owing to changes in environment or life style, rendering formerly adaptive traits non-functional or even maladaptive. It remains largely unknown if such decay would stem from multiple mutations with small effects or rather involve few loci with major phenotypic effects. Here, we investigate the decay of female sexual traits, and the genetic causes thereof, in a transition from haplodiploid sexual reproduction to endosymbiont-induced asexual reproduction in the parasitoid wasp Asobara japonica. We take advantage of the fact that asexual females cured of their endosymbionts produce sons instead of daughters, and that these sons can be crossed with sexual females. By combining behavioral experiments with crosses designed to introgress alleles from the asexual into the sexual genome, we found that sexual attractiveness, mating, egg fertilization and plastic adjustment of offspring sex ratio (in response to variation in local mate competition) are decayed in asexual A. japonica females. Furthermore, introgression experiments revealed that the propensity for cured asexual females to produce only sons (because of decayed sexual attractiveness, mating behavior and/or egg fertilization) is likely caused by recessive genetic effects at a single locus. Recessive effects were also found to cause decay of plastic sex-ratio adjustment under variable levels of local mate competition. Our results suggest that few recessive mutations drive decay of female sexual traits, at least in asexual species deriving from haplodiploid sexual ancestors.
Development of a Nasonia vitripennis outbred laboratory population for genetic analysis
Zande, L. van de; Ferber, S. ; Haan, A. de; Beukeboom, L.W. ; Heerwaarden, J. van; Pannebakker, B.A. - \ 2014
Molecular Ecology Resources 14 (2014)3. - ISSN 1755-098X - p. 578 - 587.
parasitoid wasp nasonia - local mate competition - sex-ratio - drosophila-melanogaster - natural-populations - ectoparasitic wasp - hymenoptera - genome - evolution - recombination
The parasitoid wasp genus Nasonia has rapidly become a genetic model system for developmental and evolutionary biology. The release of its genome sequence led to the development of high-resolution genomic tools, for both interspecific and intraspecific research, which has resulted in great advances in understanding Nasonia biology. To further advance the utility of Nasonia vitripennis as a genetic model system and to be able to fully exploit the advantages of its fully sequenced and annotated genome, we developed a genetically variable and well-characterized experimental population. In this study, we describe the establishment of the genetically diverse HVRx laboratory population from strains collected from the field in the Netherlands. We established a maintenance method that retains genetic variation over generations of culturing in the laboratory. As a characterization of its genetic composition, we provide data on the standing genetic variation and estimate the effective population size (Ne ) by microsatellite analysis. A genome-wide description of polymorphism is provided through pooled resequencing, which yielded 417 331 high-quality SNPs spanning all five Nasonia chromosomes. The HVRx population and its characterization are freely available as a community resource for investigators seeking to elucidate the genetic basis of complex trait variation using the Nasonia model system
Footprints of selection in wild populations of Bicyclus anynana along a latitudinal cline
Jong, M.A. de; Collins, S. ; Beldade, P. ; Brakefield, P.M. ; Zwaan, B.J. - \ 2013
Molecular Ecology 22 (2013)2. - ISSN 0962-1083 - p. 341 - 353.
drosophila-melanogaster - eastern australia - life-history - genetic responses - stress resistance - wing pattern - evolution - polymorphism - divergence - adaptation
One of the major questions in ecology and evolutionary biology is how variation in the genome enables species to adapt to divergent environments. Here, we study footprints of thermal selection in candidate genes in six wild populations of the afrotropical butterfly Bicyclus anynana sampled along a c. 3000 km latitudinal cline. We sequenced coding regions of 31 selected genes with known functions in metabolism, pigment production, development and heat shock responses. These include genes for which we expect a priori a role in thermal adaptation and, thus, varying selection pressures along a latitudinal cline, and genes we do not expect to vary clinally and can be used as controls. We identified amino acid substitution polymorphisms in 13 genes and tested these for clinal variation by correlation analysis of allele frequencies with latitude. In addition, we used two FST-based outlier methods to identify loci with higher population differentiation than expected under neutral evolution, while accounting for potentially confounding effects of population structure and demographic history. Two metabolic enzymes of the glycolytic pathway, UGP and Treh, showed clinal variation. The same loci showed elevated population differentiation and were identified as significant outliers. We found no evidence of clines in the pigmentation genes, heat shock proteins and developmental genes. However, we identified outlier loci in more localized parts of the range in the pigmentation genes yellow and black. We discuss that the observed clinal variation and elevated population divergence in UGP and Treh may reflect adaptation to a geographic thermal gradient.
The scent of inbreeding: a male sex pheromone betrays inbred males
Bergen, E. van; Brakefield, P.M. ; Heuskin, S. ; Zwaan, B.J. ; Nieberding, C.M. - \ 2013
Proceedings of the Royal Society. B: Biological Sciences 280 (2013)1758. - ISSN 0962-8452
butterfly bicyclus-anynana - mate-choice - drosophila-melanogaster - male courtship - genetic load - teleogryllus-commodus - morphological traits - life-history - depression - heterozygosity
Inbreeding depression results from mating among genetically related individuals and impairs reproductive success. The decrease in male mating success is usually attributed to an impact on multiple fitness-related traits that reduce the general condition of inbred males. Here, we find that the production of the male sex pheromone is reduced significantly by inbreeding in the butterfly Bicyclus anynana. Other traits indicative of the general condition, including flight performance, are also negatively affected in male butterflies by inbreeding. Yet, we unambiguously show that only the production of male pheromones affects mating success. Thus, this pheromone signal informs females about the inbreeding status of their mating partners. We also identify the specific chemical component (hexadecanal) probably responsible for the decrease in male mating success. Our results advocate giving increased attention to olfactory communication as a major causal factor of mate-choice decisions and sexual selection
Interpreting experimental data on egg production - applications of dynamic differential equations
France, J. ; Lopez, S. ; Kebreab, E. ; Dijkstra, J. - \ 2013
Poultry Science 92 (2013)9. - ISSN 0032-5791 - p. 2498 - 2508.
drosophila-melanogaster - gastrointestinal-tract - quantitative genetics - mathematical-models - phosphorus - calcium - absorption - fertility - algorithm
This contribution focuses on applying mathematical models based on systems of ordinary first-order differential equations to synthesize and interpret data from egg production experiments. Models based on linear systems of differential equations are contrasted with those based on nonlinear systems. Regression equations arising from analytical solutions to linear compartmental schemes are considered as candidate functions for describing egg production curves, together with aspects of parameter estimation. Extant candidate functions are reviewed, a role for growth functions such as the Gompertz equation suggested, and a function based on a simple new model outlined. Structurally, the new model comprises a single pool with an inflow and an outflow. Compartmental simulation models based on nonlinear systems of differential equations, and thus requiring numerical solution, are next discussed, and aspects of parameter estimation considered. This type of model is illustrated in relation to development and evaluation of a dynamic model of calcium and phosphorus flows in layers. The model consists of 8 state variables representing calcium and phosphorus pools in the crop, stomachs, plasma, and bone. The flow equations are described by Michaelis-Menten or mass action forms. Experiments that measure Ca and P uptake in layers fed different calcium concentrations during shell-forming days are used to evaluate the model. In addition to providing a useful management tool, such a simulation model also provides a means to evaluate feeding strategies aimed at reducing excretion of potential pollutants in poultry manure to the environment.
Absence of complementary sex determination in the parasitoid wasp genus asobara (hymenoptera: braconidae)
Ma, W.J. ; Kuijper, B. ; Boer, J.G. de; Zande, L. van de; Beukeboom, L.W. ; Wertheim, B. ; Pannebakker, B.A. - \ 2013
PLoS ONE 8 (2013)4. - ISSN 1932-6203 - 9 p.
nasonia-vitripennis hymenoptera - tabida nees braconidae - drosophila-melanogaster - cotesia-vestalis - determining mechanisms - inbreeding depression - determination pathway - diploid males - populations - models
An attractive way to improve our understanding of sex determination evolution is to study the underlying mechanisms in closely related species and in a phylogenetic perspective. Hymenopterans are well suited owing to the diverse sex determination mechanisms, including different types of Complementary Sex Determination (CSD) and maternal control sex determination. We investigated different types of CSD in four species within the braconid wasp genus Asobara that exhibit diverse life-history traits. Nine to thirteen generations of inbreeding were monitored for diploid male production, brood size, offspring sex ratio, and pupal mortality as indicators for CSD. In addition, simulation models were developed to compare these observations to predicted patterns for multilocus CSD with up to ten loci. The inbreeding regime did not result in diploid male production, decreased brood sizes, substantially increased offspring sex ratios nor in increased pupal mortality. The simulations further allowed us to reject CSD with up to ten loci, which is a strong refutation of the multilocus CSD model. We discuss how the absence of CSD can be reconciled with the variation in life-history traits among Asobara species, and the ramifications for the phylogenetic distribution of sex determination mechanisms in the Hymenoptera
Exploitation of Chemical Signaling by Parasitoids: Impact on Host Population Dynamics
Lof, M.E. ; Gee, M. de; Dicke, M. ; Gort, G. ; Hemerik, L. - \ 2013
Journal of Chemical Ecology 39 (2013)6. - ISSN 0098-0331 - p. 752 - 763.
induced plant volatiles - drosophila-melanogaster - spatial dynamics - natural enemies - spatiotemporal dynamics - ecological perspective - leptopilina-heterotoma - aggregation pheromone - mediated aggregation - species coexistence
Chemical information mediates species interactions in a wide range of organisms. Yet, the effect of chemical information on population dynamics is rarely addressed. We designed a spatio-temporal parasitoid—host model to investigate the population dynamics when both the insect host and the parasitic wasp that attacks it can respond to chemical information. The host species, Drosophila melanogaster, uses food odors and aggregation pheromone to find a suitable resource for reproduction. The larval parasitoid, Leptopilina heterotoma, uses these same odors to find its hosts. We show that when parasitoids can respond to food odors, this negatively affects fruit fly population growth. However, extra parasitoid responsiveness to aggregation pheromone does not affect fruit fly population growth. Our results indicate that the use of the aggregation pheromone by D. melanogaster does not lead to an increased risk of parasitism. Moreover, the use of aggregation pheromone by the host enhances its population growth and enables it to persist at higher parasitoid densities.
Acclimation responses to temperature vary with vertical stratification: implications for vulnerability of soil-dwelling species to extreme temperature events
Dooremalen, C. van; Berg, M.P. ; Ellers, J. - \ 2013
Global Change Biology 19 (2013)3. - ISSN 1354-1013 - p. 975 - 984.
fatty-acid-composition - springtail orchesella-cincta - membrane-lipid-composition - chill coma recovery - scots pine forest - drosophila-melanogaster - climate-change - phenotypic plasticity - entomopathogenic nematodes - environmental physiology
The occurrence of summer heat waves is predicted to increase in amplitude and frequency in the near future, but the consequences of such extreme events are largely unknown, especially for belowground organisms. Soil organisms usually exhibit strong vertical stratification, resulting in more frequent exposure to extreme temperatures for surface-dwelling species than for soil-dwelling species. Therefore soil-dwelling species are expected to have poor acclimation responses to cope with temperature changes. We used five species of surface-dwelling and four species of soil-dwelling Collembola that habituate different depths in the soil. We tested for differences in tolerance to extreme temperatures after acclimation to warm and cold conditions. We also tested for differences in acclimation of the underlying physiology by looking at changes in membrane lipid composition. Chill coma recovery time, heat knockdown time and fatty acid profiles were determined after 1 week of acclimation to either 5 or 20 °C. Our results showed that surface-dwelling Collembola better maintained increased heat tolerance across acclimation temperatures, but no such response was found for cold tolerance. Concordantly, four of the five surface-dwelling Collembola showed up to fourfold changes in relative abundance of fatty acids after 1 week of acclimation, whereas none of the soil-dwelling species showed a significant adjustment in fatty acid composition. Strong physiological responses to temperature fluctuations may have become redundant in soil-dwelling species due to the relative thermal stability of their subterranean habitat. Based on the results of the four species studied, we expect that unless soil-dwelling species can temporarily retreat to avoid extreme temperatures, the predicted increase in heat waves under climatic change renders these soil-dwelling species more vulnerable to extinction than species with better physiological capabilities. Being able to act under a larger thermal range is probably costly and could reduce maximum performance at the optimal temperature
Noncoding flavivirus RNA displays RNA interference suppressor activity in insect and Mammalian cells
Schnettler, E. ; Sterken, M.G. ; Leung, J.Y. ; Metz, S.W.H. ; Geertsma, C. ; Goldbach, R.W. ; Vlak, J.M. ; Kohl, A. ; Kromykh, A.A. ; Pijlman, G.P. - \ 2012
Journal of Virology 86 (2012)24. - ISSN 0022-538X - p. 13486 - 13500.
animal virus-replication - antiviral immunity - drosophila-melanogaster - arbovirus infection - secondary structure - subgenomic rna - ns3 protein - kunjin ns3 - micrornas - expression
West Nile virus (WNV) and dengue virus (DENV) are highly pathogenic, mosquito-borne flaviviruses (family Flaviviridae) that cause severe disease and death in humans. WNV and DENV actively replicate in mosquitoes and human hosts and thus encounter different host immune responses. RNA interference (RNAi) is the predominant antiviral response against invading RNA viruses in insects and plants. As a countermeasure, plant and insect RNA viruses encode RNA silencing suppressor (RSS) proteins to block the generation/activity of small interfering RNA (siRNA). Enhanced flavivirus replication in mosquitoes depleted for RNAi factors suggests an important biological role for RNAi in restricting virus replication, but it has remained unclear whether or not flaviviruses counteract RNAi via expression of an RSS. First, we established that flaviviral RNA replication suppressed siRNA-induced gene silencing in WNV and DENV replicon-expressing cells. Next, we showed that none of the WNV encoded proteins displayed RSS activity in mammalian and insect cells and in plants by using robust RNAi suppressor assays. In contrast, we found that the 3'-untranslated region-derived RNA molecule known as subgenomic flavivirus RNA (sfRNA) efficiently suppressed siRNA- and miRNA-induced RNAi pathways in both mammalian and insect cells. We also showed that WNV sfRNA inhibits in vitro cleavage of double-stranded RNA by Dicer. The results of the present study suggest a novel role for sfRNA, i.e., as a nucleic acid-based regulator of RNAi pathways, a strategy that may be conserved among flaviviruses.
Genetic variation for stress-response hormesis in C. elegans lifespan
Rodriguez Sanchez, M. ; Snoek, L.B. ; Riksen, J.A.G. ; Bevers, R.P.J. ; Kammenga, J.E. - \ 2012
Experimental Gerontology 47 (2012)8. - ISSN 0531-5565 - p. 581 - 587.
quantitative trait loci - genotype-environment interactions - nematode caenorhabditis-elegans - long-lived mutant - drosophila-melanogaster - heat-shock - history traits - natural variation - longevity - resistance
Increased lifespan can be associated with greater resistance to many different stressors, most notably thermal stress. Such hormetic effects have also been found in C. elegans where short-term exposure to heat lengthens the lifespan. Genetic investigations have been carried out using mutation perturbations in a single genotype, the wild type Bristol N2. Yet, induced mutations do not yield insight regarding the natural genetic variation of thermal tolerance and lifespan. We investigated the genetic variation of heat-shock recovery, i.e. hormetic effects on lifespan and associated quantitative trait loci (QTL) in C. elegans. Heat-shock resulted in an 18% lifespan increase in wild type CB4856 whereas N2 did not show a lifespan elongation. Using recombinant inbred lines (RILs) derived from a cross between wild types N2 and CB4856 we found natural variation in stress-response hormesis in lifespan. Approx. 28% of the RILs displayed a hormesis effect in lifespan. We did not find any hormesis effects for total offspring. Across the RILs there was no relation between lifespan and offspring. The ability to recover from heat-shock mapped to a significant QTL on chromosome II which overlapped with a QTL for offspring under heat-shock conditions. The QTL was confirmed by introgressing relatively small CB4856 regions into chromosome II of N2. Our observations show that there is natural variation in hormetic effects on C. elegans lifespan for heat-shock and that this variation is genetically determined.
West Nile virus encodes a microRNA-like small RNA in the 3' untranslated region which up-regulates GATA4 mRNA and facilitates virus replication in mosquito cells
Hussain, M. ; Torres, S. ; Schnettler, E. ; Funk, A. ; Grundhoff, A. ; Pijlman, G.P. ; Khromykh, A.A. ; Asgari, S. - \ 2012
Nucleic acids research 40 (2012)5. - ISSN 0305-1048 - p. 2210 - 2223.
double-stranded-rna - viral micrornas - gene-expression - flavivirus rna - infected-cells - aedes-aegypti - drosophila-melanogaster - antiviral immunity - vitellogenin gene - kunjin virus
West Nile virus (WNV) belongs to a group of medically important single-stranded, positive-sense RNA viruses causing deadly disease outbreaks around the world. The 3' untranslated region (3'-UTR) of the flavivirus genome, in particular the terminal 3' stem–loop (3'SL) fulfils multiple functions in virus replication and virus–host interactions. Using the Kunjin strain of WNV (WNVKUN), we detected a virally encoded small RNA, named KUN-miR-1, derived from 3'SL. Transcription of WNVKUN pre-miRNA (3'SL) in mosquito cells either from plasmid or Semliki Forest virus (SFV) RNA replicon resulted in the production of mature KUN-miR-1. Silencing of Dicer-1 but not Dicer-2 led to a reduction in the miRNA levels. Further, when a synthetic inhibitor of KUN-miR-1 was transfected into mosquito cells, replication of viral RNA was significantly reduced. Using cloning and bioinformatics approaches, we identified the cellular GATA4 mRNA as a target for KUN-miR-1. KUN-miR-1 produced in mosquito cells during virus infection or from plasmid DNA, SFV RNA replicon or mature miRNA duplex increased accumulation of GATA4 mRNA. Depletion of GATA4 mRNA by RNA silencing led to a significant reduction in virus RNA replication while a KUN-miR-1 RNA mimic enhanced replication of a mutant WNVKUN virus producing reduced amounts of KUN-miR-1, suggesting that GATA4-induction via KUN-miR-1 plays an important role in virus replication.
Natural variation in learning rate and memory dynamics in parasitoid wasps: opportunities for converging ecology and neuroscience
Hoedjes, K.M. ; Kruidhof, H.M. ; Huigens, M.E. ; Dicke, M. ; Vet, L.E.M. ; Smid, H.M. - \ 2011
Proceedings of the Royal Society. B: Biological Sciences 278 (2011)1707. - ISSN 0962-8452 - p. 889 - 897.
long-term-memory - cotesia-glomerata - drosophila-melanogaster - leptopilina-heterotoma - microplitis-croceipes - phytophagous insects - foraging success - infochemical use - apis-mellifera - c-rubecula
Although the neural and genetic pathways underlying learning and memory formation seem strikingly similar among species of distant animal phyla, several more subtle inter- and intraspecific differences become evident from studies on model organisms. The true significance of such variation can only be understood when integrating this with information on the ecological relevance. Here, we argue that parasitoid wasps provide an excellent opportunity for multi-disciplinary studies that integrate ultimate and proximate approaches. These insects display interspecific variation in learning rate and memory dynamics that reflects natural variation in a daunting foraging task that largely determines their fitness: finding the inconspicuous hosts to which they will assign their offspring to develop. We review bioassays used for oviposition learning, the ecological factors that are considered to underlie the observed differences in learning rate and memory dynamics, and the opportunities for convergence of ecology and neuroscience that are offered by using parasitoid wasps as model species. We advocate that variation in learning and memory traits has evolved to suit an insect's lifestyle within its ecological niche.
Translating environmental gradients into discontinuous reaction norms via hormone signalling in a polyphenic butterfly
Oostra, V. ; Jong, M.A. de; Invergo, B.M. ; Kesbeke, F. ; Wende, F. ; Brakefield, P.M. ; Zwaan, B.J. - \ 2011
Proceedings of the Royal Society. B: Biological Sciences 278 (2011)1706. - ISSN 0962-8452 - p. 789 - 797.
bicyclus-anynana - phenotypic plasticity - developmental plasticity - drosophila-melanogaster - starvation resistance - artificial selection - eyespot size - evolution - responses - canalization
Polyphenisms—the expression of discrete phenotypic morphs in response to environmental variation—are examples of phenotypic plasticity that may potentially be adaptive in the face of predictable environmental heterogeneity. In the butterfly Bicyclus anynana, we examine the hormonal regulation of phenotypic plasticity that involves divergent developmental trajectories into distinct adult morphs for a suite of traits as an adaptation to contrasting seasonal environments. This polyphenism is induced by temperature during development and mediated by ecdysteroid hormones. We reared larvae at separate temperatures spanning the natural range of seasonal environments and measured reaction norms for ecdysteroids, juvenile hormones (JHs) and adult fitness traits. Timing of peak ecdysteroid, but not JH titres, showed a binary response to the linear temperature gradient. Several adult traits (e.g. relative abdomen mass) responded in a similar, dimorphic manner, while others (e.g. wing pattern) showed a linear response. This study demonstrates that hormone dynamics can translate a linear environmental gradient into a discrete signal and, thus, that polyphenic differences between adult morphs can already be programmed at the stage of hormone signalling during development. The range of phenotypic responses observed within the suite of traits indicates both shared regulation and independent, trait-specific sensitivity to the hormone signal.
Changed gene expression for candidate ageing genes in long-lived Bicyclus anynana butterflies
Pijpe, J. ; Pul, N. ; Duijn, S. van; Brakefield, P.M. ; Zwaan, B.J. - \ 2011
Experimental Gerontology 46 (2011)6. - ISSN 0531-5565 - p. 426 - 434.
quantitative trait loci - extend life-span - drosophila-melanogaster - oxidative damage - caenorhabditis-elegans - starvation resistance - adaptive evolution - stress resistance - natural variation - longevity
Candidate genes for the regulation of lifespan have emerged from studies that use mutants and genetically manipulated model organisms. However, it is rarely addressed whether these genes contribute to lifespan variation in populations of these species that capture natural standing genetic variation. Here, we explore expression variation in three candidate ageing genes, Indy, sod2, and catalase, in Bicyclus anynana, a butterfly with well understood ecology. We used lines established from natural populations and artificially selected for increased adult starvation resistance. They show a considerable increase in adult lifespan under both starvation and optimal food conditions. We measured adult butterflies of various ages, under a range of optimal and starvation diets, from two selected populations and one unselected control population. In all lines, Indy and catalase are up-regulated in response to starvation while this is not evident for sod2. Under starvation, Indy and catalase are up-regulated in, while this is not evident for sod2. Under optimal food conditions, Indy is down-regulated at a later age, with Indy expression showing relatively high inter-individual variation. We find differences between the selected lines and the unselected line. Under starvation conditions, expression is higher for catalase in one, and for sod2 in both selected lines. Importantly, sod2 expression is also higher in the selected populations under optimal food conditions. We conclude that sod2, but not Indy, is involved in the response to artificial selection for increased starvation resistance. The role of catalase is less clear because of the differences between the two selected lines. Moreover, sod2 appears to be a candidate gene that underpins the genetic correlation between starvation resistance and longevity. Our study indicates that some, but not all, genes identified through mutant screens in other organisms may underpin standing genetic variation for ageing-related traits in stocks of Bicyclus butterflies established from natural populations. Clearly, this needs to be investigated in other organisms as well, especially in the organisms to which mutants screens were applied. This information will narrow down the list of genes that underpin variation in lifespan and ageing in extant populations of organisms, and which may serve as candidate genes in humans