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Cucurbitaceae plants produce cucurbitacins, bitter triterpenoids, to protect themselves against various insects and pathogens. Adult banded cucumber beetles (Diabrotica balteata), a common pest of maize and cucurbits, sequester cucurbitacins, presumably as a defensive mechanism against their natural enemies, which might reduce the efficacy of biological control agents. Whether the larvae also sequester and are protected by cucurbitacins is unclear. We profiled cucurbitacin levels in four varieties of cucumber, Cucumis sativus, and in larvae fed on these varieties. Then, we evaluated larval growth and resistance against common biocontrol organisms including insect predators, entomopathogenic nematodes, fungi and bacteria. We found considerable qualitative and quantitative differences in the cucurbitacin levels of the four cucumber varieties. While two varieties were fully impaired in their production, the other two accumulated high levels of cucurbitacins. We also observed that D. balteata larvae sequester and metabolize cucurbitacins, and although the larvae fed extensively on both belowground and aboveground tissues, the sequestered cucurbitacins were mainly derived from belowground tissues. Cucurbitacins had no detrimental effects on larval performance and, surprisingly, did not provide protection against any of the natural enemies evaluated. Our results show that D. balteata larvae can indeed sequester and transform cucurbitacins, but sequestered cucurbitacins do not impact the biocontrol potential of common natural enemies used in biocontrol. Hence, this plant trait should be conserved in plant breeding programs, as it has been demonstrated in previous studies that it can provide protection against plant pathogens and generalist insects., Journal of Pest Science, 96 (3), ISSN:1612-4758, ISSN:1612-4766

Cotton has been used as a model plant to study direct and indirect plant defence against herbivorous insects. However, the plant growing conditions could have an important effect on the outcome of such plant defence studies. We examined how common experimental growth conditions influence constitutive and inducible defences in two species of cotton, Gossypium hirsutum and G. herbaceum. We induced plants by applying caterpillar regurgitant to mechanical wounds to compare the induction levels between plants of both species grown in greenhouse or phytotron conditions. For this we measured defence metabolites (gossypol and heliocides) and performance of Spodoptera frugiperda caterpillars on different leaves, the emission of plant volatiles, and their attractiveness to parasitic wasps. Induction increased the levels of defence metabolites, which in turn decreased the performance of S. frugiperda larvae. Constitutive and induced defence levels were the highest in plants grown in the phytotron (compared to greenhouse plants), G. hirsutum and young leaves. Defence induction was more pronounced in plants grown in the phytotron and in young leaves. Also, the differences between growing conditions were more evident for metabolites in the youngest leaves, indicating an interaction with plant ontogeny. The composition of emitted volatiles was different between plants from the two growth conditions, with greenhouse-grown plants showing more variation than phytotron-grown plants. Also, G. hirsutum released higher amounts of volatiles and attracted more parasitic wasps than G. herbaceum. Overall, these results highlight the importance of experimental abiotic factors in plant defence induction and ontogeny of defences. We therefore suggest careful consideration in selecting the appropriate experimental growing conditions for studies on plant defences.

Pesticide exposure and food stress are major threats to bees, but their potential synergistic impacts under field-realistic conditions remain poorly understood and are not considered in current pesticide risk assessments. We conducted a semi-field experiment to examine the single and interactive effects of the novel insecticide flupyradifurone (FPF) and nutritional stress on fitness proxies in the solitary bee Osmia bicornis . Individually marked bees were released into flight cages with monocultures of buckwheat, wild mustard or purple tansy, which were assigned to an insecticide treatment (FPF or control) in a crossed design. Nutritional stress, which was high in bees foraging on buckwheat, intermediate on wild mustard and low on purple tansy, modulated the impact of insecticide exposure. Within the first day after application of FPF, mortality of bees feeding on buckwheat was 29 times higher compared with control treatments, while mortality of FPF exposed and control bees was similar in the other two plant species. Moreover, we found negative synergistic impacts of FPF and nutritional stress on offspring production, flight activity, flight duration and flower visitation frequency. These results reveal that environmental policies and risk assessment schemes that ignore interactions among anthropogenic stressors will fail to adequately protect bees and the pollination services they provide.

Plant secondary metabolites that are released into the rhizosphere alter biotic and abiotic soil properties, which in turn affect the performance of other plants. How such plant-soil feedbacks affect agricultural productivity and food quality in crop rotations is unknown. Here, we assessed the impact of maize benzoxazinoids on the performance, yield and food quality of three winter wheat varieties in a two-year field experiment. Following maize cultivation, we detected benzoxazinoid-dependent chemical and microbial fingerprints in the soil. The chemical fingerprint was still visible during wheat growth, while the microbial fingerprint was no longer detected. Benzoxazinoid soil conditioning by wild-type maize led to increased wheat emergence, tillering, growth and biomass compared to soil conditioning bybx1mutant plants. Weed cover remained unaffected, while insect damage decreased in a subset of varieties. Wheat yield was increased by over 4% without a reduction in grain quality across varieties. This improvement was directly associated with increased germination and tillering. Taken together, our experiments demonstrate that plant secondary metabolites can increase yield via plant-soil feedbacks under agronomically realistic conditions. If this phenomenon holds across different soils and environmental conditions, optimizing plant root exudation could be a powerful, genetically tractable strategy to enhance crop yields without additional inputs.

SummaryPlants perceive the presence and defense status of their neighbors through light and volatile cues. How plants integrate these stimuli into potentially adaptive responses is not well understood.We investigated whether changes in Red to Far red light (R:FR) ratios affect maize (Zea mays) responses to a blend of herbivore-induced plant volatiles, including the green leaf volatile (Z)-3-hexenyl acetate. By supplementing FR and using aphyB1phyB2maize mutant that is unresponsive to FR, we modulated light signaling and perception and determined defense-related gene expression, hormone accumulation, and volatile release in response to (Z)-3-hexenyl acetate.Exposure to (Z)-3-hexenyl acetate induced maize volatile release. Short-term FR supplementation increased this response in seedlings and older plants. FR enhanced (Z)-3-hexenyl acetate-induced JA-Ile levels, stomatal opening, and photosynthesis. In contrast to short-term FR supplementation, thephyB1phyB2mutant displayed reduced responsiveness to (Z)-3-hexenyl acetate. Short-term FR exposure was more efficient at boosting (Z)-3-hexenyl acetate-induced volatile release than long-term exposure.We conclude that short-term FR exposure enhances maize volatile emissions in response to (Z)-3-hexenyl acetate either as a short-term phyB-mediated response and/or via changes in photosynthesis and stomatal conductance. Our findings reveal interactive responses to light and volatiles cues with important consequences for plant-plant and plant-herbivore dynamics.

Plant domestication has commonly reduced levels of secondary metabolites known to confer resistance against insects. Chili pepper is a special case because the fruits of different varieties have been selected for lower and higher levels of capsaicin, the main compound associated with defense. This may have important consequences for insect herbivores and their natural enemies. Despite the widespread consumption of chili peppers worldwide, the effects of capsaicin on insects are poorly understood. Here, we investigated the effect of capsaicin on a generalist herbivore, Spodoptora latifascia (Lepidoptera: Noctuidae) and its ectoparasitoid, Euplectrus platyhypenae (Hymenoptera: Eulophidae). Using chili varieties with three pungency levels: non-pungent (Padron), mild (Cayenne) and highly pungent (Habanero), as well as artificial diets spiked with three different levels of synthetic capsaicin, we determined if higher capsaicin levels negatively affect the performance of these insects.Overall, capsaicin had a negative effect on both herbivore and parasitoid performance, particularly at high concentrations. Caterpillars reared on highly pungent fruits and high-capsaicin diet had longer development time, reduced pupation success, lower adult emergence, but also lower parasitism rates than caterpillars reared on mild or non-capsaicin treatments. In addition, we found that the caterpillars were capable of sequestering capsaicinoids in their haemolymph when fed on the high pungent variety with consequences for parasitoids’ performance and oviposition decisions. These results increase our understanding of the role of capsaicin as a chemical defense against insects and its potential implications for pest management.

1. Theory predicts that a large fraction of phytochemical diversity—the richness of individual chemical compounds produced by plants—governs the complexity of interactions between plants and their herbivores. While the effect of specific classes of chemical compounds on plant resistance against herbivores has been largely documented, the effect of community-level variation in phytochemical diversity on plant–herbivore interactions has so far received minimal consideration. 2. We hypothesized that plant communities bearing on average higher levels of phytochemical diversity should sustain lower herbivory rates, overall. Yet, the magnitude of this effect could vary across different environmental conditions, potentially because of climate-mediated effects on phytochemical production and changes in herbivore community richness and composition. 3. To address these hypotheses, we used previous knowledge of species-level phytochemical make-up for more than 400 plant species of the Swiss Alps. Using common garden experiments, we estimated season-wide herbivore damage on low (average 3,500 unique molecules) and high (average 4,500 unique molecules) phytochemical diversity plant communities that were planted in the colline, mountain and alpine vegetation sites along two elevation transects in the Alps. 4. We found that high phytochemical diversity plant communities showed reduced levels of herbivore damage in the colline (low elevation) sites, but this pattern reversed in the alpine (high elevation) sites. Our results suggest that the outcome of phytochemical diversity on plant–herbivore interactions depends on the characteristics of the local herbivore communities, together with trade-offs between chemical defences and other plant traits (i.e. physical defences and plant palatability). 5. Synthesis. Phytochemical diversity is a key component of functional diversity, influencing community composition and dynamics. We show that the effect of phytochemical diversity on herbivory is environmental-dependent, generating ecological switches when moving from low to high elevation. Through upward movement of plants under climate change, phytochemical community structure will be likely modified, ultimately disrupting local community assembly processes. ISSN:0022-0477

The ubiquitous use of agrochemicals is one driver for the ongoing loss of insect biomass and diversity. Data show that field‐realistic concentrations of neonicotinoid insecticides can negatively affect both population density and the fitness of solitary bees. However, the underlying mechanisms for these effects remain poorly understood. Here, using an established semi‐field experimental set‐up and Osmia cornuta as a solitary bee model, we examined the effects of field‐realistic concentrations of a common neonicotinoid insecticide (clothianidin) on male larvae and adults. Besides measuring lethal (i.e., overwintering success and adult survival) and sub‐lethal endpoints (i.e., emergence mass and emergence duration), we examined, for the first time, potential effects on the male reproductive physiology of a solitary bee (i.e., sperm quantity and viability). The data revealed no significant effects on any of the measured response variables. This may be due to the low degree of clothianidin exposure (0.56 ng g−1) and/or the apparent low susceptibility of solitary bee larvae to neonicotinoids. Furthermore, it is conceivable that ideal foraging conditions, combined with optimal weather and lack of other environmental stressors, may have improved the ability of bees to cope with the insecticide. To reliably assess and understand the environmental hazards of agrochemicals, a holistic approach, including laboratory, semi‐field and field data is required. Knowledge of underlying mechanisms will help to mitigate the current global declines of insect populations.

Most land plants entertain a mutualistic symbiosis known as arbuscular mycorrhiza with fungi (Glomeromycota) that provide them with essential mineral nutrients, in particular phosphate (Pi), and protect them from biotic and abiotic stress. Arbuscular mycorrhizal (AM) symbiosis increases plant productivity and biodiversity and is therefore relevant for both natural plant communities and crop production. However, AM fungal populations suffer from intense farming practices in agricultural soils, in particular Pi fertilization. The dilemma between natural fertilization from AM symbiosis and chemical fertilization has raised major concern and emphasizes the need to better understand the mechanisms by which Pi suppresses AM symbiosis. Here, we test the hypothesis that Pi may interfere with AM symbiosis via the phytohormone gibberellic acid (GA) in the Solanaceous model systems Petunia hybrida and Nicotiana tabacum. Indeed, we find that GA is inhibitory to AM symbiosis and that Pi may cause GA levels to increase in mycorrhizal roots. Consistent with a role of endogenous GA as an inhibitor of AM development, GA-defective N. tabacum lines expressing a GA-metabolizing enzyme (GA methyltransferase—GAMT) are colonized more quickly by the AM fungus Rhizoglomus irregulare, and exogenous Pi is less effective in inhibiting AM colonization in these lines. Systematic gene expression analysis of GA-related genes reveals a complex picture, in which GA degradation by GA2 oxidase plays a prominent role. These findings reveal potential targets for crop breeding that could reduce Pi suppression of AM symbiosis, thereby reconciling the advantages of Pi fertilization with the diverse benefits of AM symbiosis.

Neonicotinoid insecticides, the most widely used category of insecticides for 20 years and candidate risk of neurodevelopment, have been detected in human urine and in hair. If the former reflecting dietary contamination over short periods and the latter total exposure over longer periods is not known. We quantified and compared the concentrations in spot urine by LC-MS/MS and in hair by UHPLC-MS/MS.In the first study, samples from an international group of scientists in Italy in 2016 (M/F=12/7),detection rate in urine and in hair was 0% vs 85.0% for imidacloprid; 0% vs 52.5% for thiacloprid; 0% vs 45.0% for acetamiprid; 0% vs 25.0% for thiamethoxam; and 0% vs 17.5% for clothianidin.In the second study, samples from 99 volunteers in three islands of the Philippines in 2017,detection rate in urine and in hair was 48.5% vs 60.6% for imidacloprid; 1.0% vs 8.1% for thiacloprid; 10.1% vs 13.1% for acetamiprid; 31.3% vs 30.3% for thiamethoxam; and 14.1% vs 45.5% for clothianidin. In the Philippine, concentrations were negatively correlated between urine and hair for thiamethoxam (r = -0.70, p = 0.016), but not for clothianidin or imidacloprid. Both analyses of urine and hair are complementary to assess human neonicotinoid exposure.

Herbivory is fundamental to the regulation of both global food webs and the extent of agricultural crop losses. Induced plant responses to herbivores promote resistance and often involve the perception of specific herbivore-associated molecular patterns (HAMPs); however, precisely defined receptors and elicitors associated with herbivore recognition remain elusive. Here, we show that a receptor confers signaling and defense outputs in response to a defined HAMP common in caterpillar oral secretions (OS). Staple food crops, including cowpea (Vigna unguiculata) and common bean (Phaseolus vulgaris), specifically respond to OS via recognition of proteolytic fragments of chloroplastic ATP synthase, termed inceptins. Using forward-genetic mapping of inceptin-induced plant responses, we identified a corresponding leucine-rich repeat receptor, termed INR, specific to select legume species and sufficient to confer inceptin-induced responses and enhanced defense against armyworms (Spodoptera exigua) in tobacco. Our results support the role of plant immune receptors in the perception of chewing herbivores and defense.

1. Ecotypic differences in plant growth and anti‐herbivore defence phenotypes are determined by the complex interactions between the abiotic and the biotic environment. 2. Root‐associated microbes (RAMs) are pervasive in nature, vary over climatic gradients and have been shown to influence the expression of multiple plant functional traits related to biomass accumulation and biotic interactions. We addressed how variation in climatic conditions between lowland and subalpine habitats in the Alps and RAMs can independently or interactively affect plant growth and anti‐herbivore defence trait expression. 3. To address the contribution of climate and RAMs on growth and chemical defences of high‐ and low‐elevation Plantago major ecotypes, we performed a full‐factorial reciprocal transplant field experiment at two elevations. We coupled it with plant functional trait measurements and metabolomics analyses. 4. We found that local growing climatic conditions mostly influenced how the ecotypes grew, but we also found that the high‐ and low‐elevation ecotypes improved biomass accumulation if in the presence of their own‐elevation RAMs. We also found that while chemical defence expression was affected by climate, they were also more highly expressed when plants were inoculated with low‐elevation RAMs. 5. Synthesis: Our research demonstrated that root‐associated microbes (RAMs) from contrasted elevations impact how plants grow or synthesize toxic secondary metabolites. At low elevation, where biotic interactions are stronger, RAMs enhance plant biomass accumulation and the production of toxic secondary metabolites.

Multiple chloroplast-to-nucleus signaling pathways contribute to the regulation of chloroplast biogenesis during plant greening. Here, we provide evidence for the direct implication of the atypical kinase ABC1K1. ABC1K1 is required for sufficient plastoquinone (PQ) allocation to the photosynthetic electron transport chain. Unexpectedly, mutation of abc1k1 suppresses greening and results in pale cotyledons under red light. This phenotype was not observed in other photosynthetic mutants and points to a specific signaling defect. Under red light, abc1k1 accumulated EXECUTER1 (EX1), a trigger of singlet oxygen (1O2) signaling. Consistent with the role of the FTSH metalloprotease in chloroplast biogenesis and EX1 degradation, the ftsh2 mutant var2, mimicked the greening defect of abc1k1 and accumulated EX1 under red light. We propose that this novel ABC1K1-dependent signal is required for chloroplast biogenesis to progress in challenging light conditions.

Plasma membrane-associated and intracellular proteins and protein complexes play a pivotal role in pathogen recognition and disease resistance signaling in plants and animals. The two predominant protein families perceiving plant pathogens are receptor-like kinases and nucleotide binding-leucine-rich repeat receptors (NLR), which often confer race-specific resistance. Leaf rust is one of the most prevalent and most devastating wheat diseases. Here, we clone the race-specific leaf rust resistance gene Lr14a from hexaploid wheat. The cloning of Lr14a is aided by the recently published genome assembly of ArinaLrFor, an Lr14a-containing wheat line. Lr14a encodes a membrane-localized protein containing twelve ankyrin (ANK) repeats and structural similarities to Ca2+-permeable non-selective cation channels. Transcriptome analyses reveal an induction of genes associated with calcium ion binding in the presence of Lr14a. Haplotype analyses indicate that Lr14a-containing chromosome segments were introgressed multiple times into the bread wheat gene pool, but we find no variation in the Lr14a coding sequence itself. Our work demonstrates the involvement of an ANK-transmembrane (TM)-like type of gene family in race-specific disease resistance in wheat. This forms the basis to explore ANK-TM-like genes in disease resistance breeding., Winter wheat cultivar Forno harbors a race-specific leaf rust resistance locus Lr14a, but the causative gene is unknown. Here, the authors show that Lr14a encodes a membrane-localized protein containing ankyrin repeats and Lr14a-containing segments have been introgressed into the bread wheat gene pool multiple times.

Plant-soil feedbacks refer to effects on plants that are mediated by soil modifications caused by the previous plant generation. Maize conditions the surrounding soil by secretion of root exudates including benzoxazinoids (BXs), a class of bioactive secondary metabolites. Previous work found that a BX-conditioned soil microbiota enhances insect resistance while reducing biomass in the next generation of maize plants. Whether these BX-mediated and microbially driven feedbacks are conserved across different soils and response species is unknown. We found the BX-feedbacks on maize growth and insect resistance conserved between two arable soils, but absent in a more fertile grassland soil, suggesting a soil-type dependence of BX feedbacks. We demonstrated that wheat also responded to BX-feedbacks. While the negative growth response to BX-conditioning was conserved in both cereals, insect resistance showed opposite patterns, with an increase in maize and a decrease in wheat. Wheat pathogen resistance was not affected. Finally and consistent with maize, we found the BX-feedbacks to be cultivar-specific. Taken together, BX-feedbacks affected cereal growth and resistance in a soil and genotype-dependent manner. Cultivar-specificity of BX-feedbacks is a key finding, as it hides the potential to optimize crops that avoid negative plant-soil feedbacks in rotations., Plant, Cell & Environment, 44 (12), ISSN:0140-7791, ISSN:1365-3040

Pesticide metabolites are frequently detected in groundwater at concentrations often exceeding those of their parent pesticides. A well-known example is the metabolites of chlorothalonil, a non-systematic, broad spectrum fungicide. Some of the chlorothalonil metabolites occur frequently and at elevated concentrations in groundwater, which is why the use of chlorothalonil was recently banned in the European Union. To estimate the long-term evolution of the concentration of the chlorothalonil metabolites in groundwater after this ban, it is important to know if metabolite residues in soil and unsaturated zone can affect the concentrations in groundwater. We developed and validated a method for the determination of 5 chlorothalonil metabolites in soil (R471811, R417888, SYN507900, SYN548580 and R611968), including those which are frequently detected in groundwater. The developed protocols, based on a solid phase extraction approach (for R471811, R417888, SYN507900, SYN548580) or a QuEChERS approach (for R611968) followed by UHPLC-MS/MS analysis, provided excellent sensitivity (LOQ of 0.5 µg/kg for all metabolites), precision (RSD

Early life adverse conditions can have major consequences on an individual’s life history traits. Oxidative stress has been hypothesized to be one main mechanism underlying the negative consequences of early life adverse conditions. To test this hypothesis, we restricted the food availability of Seba’s short-tailed bat (Carollia perspicillata) mothers of unweaned pups for 10 days, followed by ad libitum provisioning. We also had a control, unrestricted group. We explored the morphological consequences of dietary restriction during early life by measuring growth rate. We also measured four markers of blood oxidative balance during growth. We assessed the level of cortisol, and its inactive form cortisone, in the hair of the pups at the end of growth. Finally, we monitored survival during the first year. Food restriction triggered a slowdown in growth followed by catch-up growth when ad libitum feeding was restored which did not lead to full compensation in size or mass compared to control individuals. We found that higher growth rate was associated with elevated oxidative damage, suggesting an oxidative cost to growth. However, we found no clear evidence for physiological costs specific to the catch-up growth. Survival after a year was not impacted by the treatment, the oxidative balance or the level of glucocorticoids at the end of growth. In conclusion, our results show that individuals were able to efficiently mitigate the short-term consequences of adverse early life conditions. However, consequences might arise in the long-term, and could impact reproductive success or lifespan.

Ultraviolet (UV) radiation has emerged as an environmental cue with potential uses to enhance plant protection against arthropod pests in agriculture. UV can augment constitutive and inducible plant defenses against herbivorous arthropods. Here we investigated whether application of supplemental UV to chrysanthemum (Chrysanthemum × morifolium Ramat) cuttings during their rooting phase enhanced plant resistance to an important insect pest, Western flower thrips (Frankliniella occidentalis). For this, we analyzed how several daily UV exposure times affected plant damage by thrips on three different chrysanthemum cultivars. The most effective UV dose and responsive cultivar were further used to determine the UV effects on host plant preference by thrips, leaf metabolome and the induction of jasmonic acid (JA)-associated defenses. Our results showed that while short UV daily exposure times increased chrysanthemum resistance to thrips, longer exposure times had the opposite effect. Furthermore, we showed that UV-mediated induction of chrysanthemum resistance to thrips was genotype dependent and can persist after the end of the of the UV treatment. Yet, this induction was not transferred to the next generation from mother plants to cuttings. Nontargeted metabolomic, enzymatic and hormone analyses further revealed that UV slightly affected the leaf metabolome of chrysanthemum plants, and it enhanced the induction of JA-associated signaling after thrips infestation. Taken together, our results suggest that supplemental UV might modulate both constitutive and inducible chrysanthemum defenses against thrips.

A novel class of species-specific modular ascarosides that integrate additional fatty acid building blocks was characterized in the nematode Caenorhabditis remanei using a combination of HPLC-ESI-(-)-MS/MS precursor ion scanning, microreactions, HR-MS/MS, MSn, and NMR techniques. The structure of the dominating component carrying a cyclopropyl fatty acid moiety was established by total synthesis. Biogenesis of this female-produced male attractant depends on cyclopropyl fatty acid synthase (cfa), which is expressed in bacteria upon entering their stationary phase.

Neonicotinoids are the most widely used class of insecticides globally. However, the link between farming practices and the extent of contamination of soils and crops by neonicotinoid insecticides, as well as the extent of such contamination in organic fields and ecological focus areas (EFAs) are currently unclear. We measured the concentrations of five neonicotinoid insecticides (imidacloprid, clothianidin, thiamethoxam, thiacloprid, acetamiprid) in 702 soil and plant samples in 169 cultivated fields and EFAs from 62 conventional, integrated production and organic farms distributed over the entire lowland of Switzerland. We detected neonicotinoids in 93% of organic soils and crops, and more than 80% of EFA soils and plants—two types of arable land supposedly free of insecticides. We also tested 16 samples of organic seeds, of which 14 were positive for neonicotinoids. Finally, we calculated hazard quotients (HQs) and potentially affected fractions for 72 beneficial and 12 pest species. Under a field‐realistic scenario, we found that between 5.3%–8.6% of above‐ground invertebrate species may be exposed to lethal concentrations of clothianidin, and 31.6%–41.2% to sublethal concentrations, in “integrated production” and conventional fields. We also found that 1.3%–6.8% (up to 12.5% based on HQs) of the beneficial invertebrate species may be exposed to sublethal concentrations of neonicotinoids in EFAs and organic fields. In contrast, no pest species would be exposed to lethal concentrations, even under a worst‐case scenario. Synthesis and applications. Our study suggests that diffuse contamination by neonicotinoids may harm a significant fraction of non‐target beneficial species. The use of neonicotinoids on crops may threaten biodiversity in refuge areas, while also potentially jeopardizing the practice of organic farming by impeding the biological control of pests. On the basis of our results, we call for a reduction in the dispersion and overuse of neonicotinoid insecticides in order to prevent any detrimental effects on biodiversity and ecosystem services associated with agroecosystems.

The massive use of neonicotinoid insecticides has been repeatedly incriminated for their impacts to avian populations. Some studies have reported contamination of granivorous birds by neonicotinoids but very little is known about exposure to neonicotinoids in other bird species. To fill this lack of knowledge, we trapped house sparrows Passer domesticus, an omnivorous bird whose diet is composed of both grains and insects, and we collected 617 feathers from individuals living on 47 conventional, integrated-production (IP-Suisse) and organic farms distributed all over the Swiss plateau, the country's main agricultural area. We then assessed the concentration of five neonicotinoids in 146 pools of feathers. We found that all feather samples were contaminated by at least one neonicotinoid at measurable concentration (>LOQ), with thiacloprid accounting for most of the prevalence (99%), while clothianidin was found at highest concentrations (with averages ranging from 1.68 to 9.2 ppb). Additionally, house sparrows living on conventional farms showed higher concentrations of neonicotinoids (15.26 ± 3.58 ppb) than individuals living on IP-Suisse (3.38 ± 0.86 ppb), and organic farms (2.59 ± 0.56 ppb). Our large-scale survey highlights how ubiquitous neonicotinoid insecticides have become in agricultural habitats, and reveals generalized exposure of house sparrows, and potentially other species inhabiting farmlands, to neonicotinoids.

To reproduce, males have to fertilize the female’s eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba’s short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates’ oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba’s short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.

Along ecological gradients, ecotypes generally evolve as the result of local adaptation to a specific environment to maximize organisms’ fitness. Alongside ecotypic differentiation, phenotypic plasticity, as the ability of a single genotype to produce different phenotypes under different environmental conditions, can also evolve for favouring increased organisms’ performance in different environments. Currently, there is a lack in our understanding of how varying habitats may contribute to the differential contribution of ecotypic differentiation and plasticity in growth versus defence traits. Using reciprocal transplant-common gardens along steep elevation gradients, we evaluated patterns of ecotypic differentiation and phenotypic plasticity of two coexisting but unrelated plant species,Cardamine pratensisandPlantago major. For both species, we observed ecotypic differentiation accompanied by plasticity in growth related traits. Plants grew faster and produced more biomass when placed at low elevation. In contrast, we observed fixed ecotypic differentiation for defence and resistance traits. Generally, low elevation ecotypes produced higher chemical defences regardless of the growing elevation. Yet, some plasticity was observed for specific compounds, such as indole glucosinolates. We speculate that ecotypic differentiation in defence traits is maintained by costs of chemical defence production, while plasticity in growth traits is regulated by temperature driven growth response maximization.

In recent years, metabolomics has emerged as a pivotal approach for the holistic analysis of metabolites in biological systems. The rapid progress in analytical equipment, coupled to the rise of powerful data processing tools, now provides unprecedented opportunities to deepen our understanding of the relationships between biochemical processes and physiological or phenotypic conditions in living organisms. However, to obtain unbiased data coverage of hundreds or thousands of metabolites remains a challenging task. Among the panel of available analytical methods, targeted and untargeted mass spectrometry approaches are among the most commonly used. While targeted metabolomics usually relies on multiple-reaction monitoring acquisition, untargeted metabolomics use either data-independent acquisition (DIA) or data-dependent acquisition (DDA) methods. Unlike DIA, DDA offers the possibility to get real, selective MS/MS spectra and thus to improve metabolite assignment when performing untargeted metabolomics. Yet, DDA settings are more complex to establish than DIA settings, and as a result, DDA is more prone to errors in method development and application. Here, we present a tutorial which provides guidelines on how to optimize the technical parameters essential for proper DDA experiments in metabolomics applications. This tutorial is organized as a series of rules describing the impact of the different parameters on data acquisition and data quality. It is primarily intended to metabolomics users and mass spectrometrists that wish to acquire both theoretical background and practical tips for developing effective DDA methods.

Plant-soil feedbacks refer to effects on plants that are mediated by soil modifications caused by the previous plant generation. Maize conditions the surrounding soil by secretion of root exudates including benzoxazinoids (BXs), a class of bioactive secondary metabolites. Previous work found that a BX- conditioned soil microbiota enhances insect resistance while reducing biomass in the next generation of maize plants. Whether these BX-mediated and microbially driven feedbacks are conserved across different soils and response species is unknown. We found the BX-feedbacks on maize growth and insect resistance conserved between two arable soils, but absent in a more fertile grassland soil, suggesting a soil-type dependence of BX feedbacks. We demonstrated that wheat also responded to BX-feedbacks. While the negative growth response to BX-conditioning was conserved in both cereals, insect resistance showed opposite patterns, with an increase in maize and a decrease in wheat. Wheat pathogen resistance was not affected. Finally and consistent with maize, we found the BX-feedbacks to be cultivar specific. Taken together, BX- feedbacks affected cereal growth and resistance in a soil and genotype dependent manner. Cultivar-specificity of BX-feedbacks is a key finding, as it hides the potential to optimize crops that avoid negative plant-soil feedbacks in rotations.

International audience; Synthetic pesticides such as neonicotinoids are commonly used to treat crops in tropical regions, where data on environmental and human contamination are patchy and make it difficult to assess to what extent pesticides may harm human health, especially in less developed countries.To assess the degree of environmental and human contamination with neonicotinoids we collected soil, water and people's hair in three agricultural regions of the Philippines and analysed them by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS-MS). Five neonicotinoids, namely acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam were targeted.Residues of neonicotinoids were found in 78% of 67 soil samples from the three provinces. Total neonicotinoid loads ranged on average between 0.017 and 0.89 μg/kg in soils of rice, banana and vegetable crops, and were 130 times higher (113.5 μg/kg) in soils of a citrus grove. Imidacloprid was the most prevalent compound at an average of 0.56 μg/kg in soil while thiacloprid was below the limit of detection. Half of the eight water samples from a rice field and nearby creek contained residues of imidacloprid (mean 1.29 ng/L) and one contained thiamethoxam (0.15 ng/L). Residues of neonicotinoids were found in 81% of 99 samples of people's hair from the surveyed regions (average total concentrations 0.14 to 1.18 ng/g, maximum 350 ng/g). Hair residue levels correlated well with the concentrations of thiamethoxam and total residues in soils from the same locality (r = 0.98). The presence of thiacloprid in 15% of the hair samples but not in soil samples suggests an additional route of exposure among people, which is most likely to be through ingestion of agricultural food and drinks available in the market.

Durable disease resistance genes such as the wheat gene Lr34 are valuable sources of resistance for agricultural breeding programs. Lr34 encodes an ATP-binding cassette transporter protein involved in the transport of the phytohormone abscisic acid. Lr34 from wheat is functionally transferable to barley, maize, rice and sorghum. A pleiotropic effect of Lr34 induces the development of a senescence-like phenotype, referred to as leaf tip necrosis. We used Lr34-expressing wheat and transgenic barley plants to elucidate the role of abscisic acid in the development of leaf tip necrosis. Leaf tips in Lr34-expressing wheat and barley showed an accumulation of abscisic acid. No increase of Lr34 expression was detected in the leaf tip. Instead, the development of ectopic, Lr34-induced leaf tip necrosis after removing the leaf tip suggests an increased flux of abscisic acid towards the tip, where it accumulates and mediates the development of leaf tip necrosis. This redistribution of abscisic acid was also observed in adult transgenic barley plants with a high Lr34 expression level growing in the field and coincided with leaf tip necrosis as well as complete field resistance against Puccinia hordei and Blumeria graminis f. sp. hordei. In a barley transgenic line with a lower Lr34 expression level, a quantitative resistance against Puccinia hordei was still observed, but without a significant redistribution of abscisic acid or apparent leaf tip necrosis. Thus, our results imply that fine-tuning the Lr34 expression level is essential to balance disease resistance versus leaf tip necrosis to deploy transgenic Lr34 in breeding programs.