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Microplastics and Nanoplastics Effects on Plant−Pollinator Interaction and Pollination Biology
Abstract
Microplastics and nanoplastics (MNPs) contamination is an emerging environmental and public health concern, and these particles have been reported both in aquatic and terrestrial ecosystems. Recent studies have expanded our understanding of the adverse effects of MNPs pollution on human, terrestrial, and aquatic animals, insects, and plants. In this perspective, we describe the adverse effects of MNPs particles on pollinator and plant health and discuss the mechanisms by which MNPs disrupt the pollination process. We discuss the evidence and integrate transcriptome studies to investigate the negative effects of MNPs on the molecular biology of pollination, which may cause delay or inhibit the pollination services. We conclude by addressing challenges to plant-pollinator health from MNPs pollution and argue that such harmful effects disrupt the communication between plant and pollinator for a successful pollination process.
... Despite microplastics being considered a threat to plant reproduction, 31 to the best of our knowledge, no studies have directly addressed this issue. The only reported study related to microplastics and plant reproductive organs was conducted to determine the role of the stylar matrix in pollen tube development. ...
Microplastics, which are indicative of global change, pervade all ecosystems, and their mass surpasses the total animal biomass of Earth. Pollination, the transfer of pollen among plants, is a key process that allows for plant reproduction and plant population prevalence. Plant reproduction could be altered by microplastics at several stages: plastic-polluted animals can act as pollinators, and airborne plastic fragments can be deposited on the stigmatic surfaces of pistils, interfering with pollen−pistil interactions, clogging pollen tube development and reducing seed production. To test this hypothesis, we examined the impact of polypropylene fragments (<63 μm) deposited on stigmatic surfaces on seed production by studying the Andean-yellow monkeyflower Erythranthe lutea (Phrymaceae). We combined hand-pollination treatments and ultrastructural observations and reported the adverse effect of polypropylene fragments on seed production when this material was deposited on stigmas, but the mass and germination levels of the obtained seeds did not differ. Optical and scanning electron microscopy observations of the pollen tube ultrastructure revealed that pollen tube development was disrupted by the addition of polypropylene fragments. The results point to the potential deleterious effects of microplastics on a crucial ecosystem process, pollination, which might have consequences for most angiosperms and crop production.
... Moreover, considering environmental realistic scenarios in field studies remains a scientific gap. To our perspective, research contributing to address the following questions are crucially needed: Shah et al., 2023)? Another complex question concerns the mutual interaction/direct -indirect impact via soil microorganisms (bacteria and fungi), which play a crucial role in the soil, with consequences for ecosystem processes and services such as water dynamics, plant growth, crop yield etc. 6. Mitigation perspectives: How can we mitigate the long-term and transgenerational effects of MP and NP contamination? ...
... In recent years, environmental plastic pollution has been classified based on size: microplastics (MPs, diameter < 5 mm) and nanoplastics (NPs, diameter < 100 nm). MPs and NPs are recognised as emerging pollutants and are drawing increasing attention due to their impacts on environmental pollution and public health (Shah et al., 2023). According to different sources, there are two types: primary MPs and NPs and secondary MPs and NPs. ...
... The tropics host over 100,000 species, with approximately 220,000 species in pollinator taxonomic groups. Globally, 1500 crops require insect pollination, contributing to 3-8 % of world crop production (Cameron and Sadd, 2020;Ollerton, 2017;Shah et al., 2023). The economic prosperity and ecological balance are significantly influenced by the specific contributions of different insect pollinators, including bees, moths, and butterflies. ...
Microplastic pollution (<5 mm in size) is undoubtedly considered a massive threat to living organisms across the globe in almost all ecosystems, i.e., aquatic and terrestrial ecosystems. These microplastic particles are transferred across food chains and food webs through inhalation or ingestion by organisms. Various persistent organic pollutants and metals are known to absorb on microplastic surfaces. Insects, being the most abundant life form on the earth, are major drivers of ecosystem services. Their immense contribution to ecosystem stability, sustainability, and resilience has been acclaimed in the literature. Plastic pollution and insect interactions have been reported consistently in the last two decades globally from both aquatic and terrestrial ecosystems. Many insect groups chew and ingest plastic films including PP, PE, and PVC. Plodia interpunctella and Tenebrio molitor larvae are known to ingest and degrade polyethylene and Styrofoam, respectively. Insect pollinators transport microplastic particles to flowers, hence interfering with the pollination process. Termites and ants are known to transport microplastics in the soil. These microplastics are being ingested by insects, and vertebrate predators of insects transfer the toxic chemicals to higher trophic levels. Microplastics affect biota adversely by disturbing metabolism, reducing survival by impairing growth and development, and declining reproduction potential. This may affect endocrinal activity by interfering with hormones. Many plastic fragments can mimic hormones, which can potentially disrupt the ecological roles of many insects. In terrestrial ecosystems, microplastics can potentially interfere with the natural biocontrol of insect pests by hormonal dysregulation in the predator species, i.e., ladybird beetles, prolonging the duration of larval instars. Polyvinylchloride microplastics have been reported to negatively affect the emergence, weight, and development of Chironomus riparius. The exposure to microplastics also alters various behaviors, i.e., oviposition and foraging behavior in different species of insects.
Environmental pollution management combined with food safety represents two of the main challenges of the last decades. Soil and water contamination has historically threatened food safety. As ubiquitous pollutants, microplastics (MPs) have attracted increasing attention over the last few years. These particles can affect the balance of terrestrial, aquatic, and aerial ecosystems. Their negative impacts are intensified when they adsorb and carry toxic chemicals. They can circulate through organisms and accumulate in human beings via food and water. Physiological dysfunctions in all species continue to be reported, both in terrestrial and aquatic ecosystems. This article considers how this might be affecting the global production of food. It reports the adverse effects induced by MPs in soils, their properties and organisms growing within and upon them, including livestock and the pollinating agents necessary for plant growth. A separate section discusses the effects of MPs on aquaculture, mentioning effects on wild species, as well as farmed fish. The growing concern of the food production sector with MPs mimics that of the world with global warming; the danger is real and requires urgent attention.
Common air pollutants, such as nitrogen oxides (NOx), emitted in diesel exhaust, and ozone (O3), have been implicated in the decline of pollinating insects. Reductionist laboratory assays, focused upon interactions between a narrow range of flowering plant and pollinator species, in combination with atmospheric chemistry models, indicate that such pollutants can chemically alter floral odors, disrupting the cues that foraging insects use to find and pollinate flowers. However, odor environments in nature are highly complex and pollination services are commonly provided by suites of insect species, each exhibiting different sensitivities to different floral odors. Therefore, the potential impacts of pollution-induced foraging disruption on both insect ecology, and the pollination services that insects provide, are currently unknown. We conducted in-situ field studies to investigate whether such pollutants could reduce pollinator foraging and as a result the pollination ecosystem service that those insects provide. Using free-air fumigation, we show that elevating diesel exhaust and O3, individually and in combination, to levels lower than is considered safe under current air quality standards, significantly reduced counts of locally-occurring wild and managed insect pollinators by 62–70% and their flower visits by 83–90%. These reductions were driven by changes in specific pollinator groups, including bees, flies, moths and butterflies, and coincided with significant reductions (14–31%) in three different metrics of pollination and yield of a self-fertile test plant. Quantifying such effects provides new insights into the impacts of human-induced air pollution on the natural ecosystem services upon which we depend.
Plastic pollution accumulating in an area of the environment is considered “poorly reversible” if natural mineralization processes occurring there are slow and engineered remediation solutions are improbable. Should negative outcomes in these areas arise as a consequence of plastic pollution, they will be practically irreversible. Potential impacts from poorly reversible plastic pollution include changes to carbon and nutrient cycles; habitat changes within soils, sediments, and aquatic ecosystems; co-occurring biological impacts on endangered or keystone species; ecotoxicity; and related societal impacts. The rational response to the global threat posed by accumulating and poorly reversible plastic pollution is to rapidly reduce plastic emissions through reductions in consumption of virgin plastic materials, along with internationally coordinated strategies for waste management.
Evolutionary transitions from animal to wind pollination have occurred repeatedly during the history of the angiosperms, but the selective mechanisms remain elusive. Here, we propose that knowledge of pollen release biomechanics is critical for understanding the ecological and evolutionary processes underpinning this shift in pollination mode. Pollen release is the critical first stage of wind pollination (anemophily) and stamen properties are therefore likely to be under strong selection early in the transition. We describe current understanding of pollen release biomechanics to provide insights on the phenotypic and ecological drivers of wind pollination. Pollen release occurs when detachment forces dominate resistive forces retaining pollen within anthers. Detachment forces can be active or passive depending on whether they require energy input from the environment. Passive release is more widespread in anemophilous species and involves processes driven by steady or unsteady aerodynamic forces or turbulence-induced vibrations that shake pollen from anthers. We review empirical and theoretical studies suggesting that stamen vibration is likely to be a key mechanism of pollen release. The vibration response is governed by morphological and biomechanical properties of stamens, which may undergo divergent selection in the presence or absence of pollinators. Resistive forces have rarely been investigated for pollen within anthers, but are probably sensitive to environmental conditions and depend on flower age, varying systematically between animal-and wind-pollinated species. Animal and wind pollination are traditionally viewed as dichotomous alternatives because they are usually associated with strikingly different pollination syndromes. But this perspective has diverted attention from subtler, continuously varying traits which mediate the fluid dynamic process of pollen release. Reinterpreting the flower as a biomechanical entity that responds to fluctuating environmental forces may provide a promising way forward. We conclude by identifying several profitable areas for future research to obtain deeper insight into the evolution of wind pollination.
Microplastics (MPs) are ubiquitous and persistent pollutants, and have been detected in a wide variety of media, from soils to aquatic systems. MPs, consisting primarily of polyethylene, polypropylene, and polyacrylamide polymers, have recently been found in 12% of samples of honey collected in Ecuador. Recently, MPs have also been identified in honey bees collected from apiaries in Copenhagen, Denmark, as well as nearby semiurban and rural areas. Given these documented exposures, assessment of their effects is critical for understanding the risks of MP exposure to honey bees. Exposure to polystyrene (PS)-MPs decreased diversity of the honey bee gut microbiota, followed by changes in gene expression related to oxidative damage, detoxification, and immunity. As a result, the aim of this perspective was to investigate whether wide-spread prevalence of MPs might have unintended negative effects on health and fitness of honey bees, as well as to draw the scientific community’s attention to the possible risks of MPs to the fitness of honey bees. Several research questions must be answered before MPs can be considered a potential threat to bees.
As emerging contaminants, microplastics (mPS, < 5 mm) have been reported to adversely affect the plant growth; however, , the mechanisms of mPS-induced growth limitation are rarely known. Here, it was found that the plastic particles were absorbed and accumulated in barley plants, which limited the development of rootlets. The mPS-treated plants had significantly higher concentrations of H2O2 and O2- in roots than the control. The mPS significantly increased the activities of dehydroascorbate reductase, glutathione reductase, ADP-Glucose pyrophosphorylase, fructokinase and phosphofructokinase, while decreased the activities of cell wall peroxidase, vacuolar invertase, sucrose synthase, phosphoglucomutase, glucose-6-phosphate dehydrogenase and phosphoglucoisomerase in roots. The changes in activities of carbohydrate and ROS metabolism enzymes in leaves showed a different trend from that in roots. The mPS plants possessed a higher trans-zeatin concentration while lower concentrations of indole-3-acetic acid, indole-3-butyric acid and dihydrozeatin than the control plants in leaves. However, the phytohormone changes in roots were distinct from those in leaves under mPS. In addition, significant correlations between enzyme activities and phytohormone concentrations were found. It was suggested that the phytohormone regulatory network plays key roles in regulating the activities of key enzymes involved in carbohydrate and ROS metabolisms in response to mPS in barley.
Microplastics are ubiquitous and their sampling is a difficult task. Honeybees interact with the environment inside their foraging range and take pollutants with them. In this work, we demonstrated for the first time that worker bees can act as active samplers of microplastics. We collected honeybees from apiaries located in the centre of Copenhagen and from nearby semiurban and rural areas. We showed the presence of microplastics in all sampled locations mostly in the form of fragments (52 %) and fibres (38 %) with average equivalent diameter of 64 ± 39 μm for fibres and 234 ± 156 μm for fragments. The highest load corresponded to urban apiaries, but comparable number of microplastics was found in hives from suburban and rural areas, which can be explained by the presence of urban settlements inside the foraging range of worker bees and to the easy dispersion of small microplastics by wind. Micro-FTIR analysis confirmed the presence of thirteen synthetic polymers, the most frequently of which was polyester followed by polyethylene and polyvinyl chloride. Our results demonstrated the presence of microplastics attached to the body of the honeybees and opens a new research pathway to their use as active biosamplers for anthropogenic pollution.
Although microplastics’ (MPs) toxicity has been reported in several aquatic and terrestrial organisms, the knowledge about how these pollutants can affect insects at the early developmental stage remains incipient. Thus, the aim of this study was to use Culex quinquefasciatus larvae as a model system to test the hypothesis that, besides accumulating in animals, polyethylene microplastics (PE MPs) lead to biochemical changes predictive of nutritional impacts, as well as induce oxidative stress, redox state imbalance, and neurotoxicity in them. Our results have indicated that short exposure to PE MPs (5 days) at the environmental concentration of 4.24 x 106 particles m-3 induced changes suggesting damage to energy metabolism such as reduced total proteins, total soluble carbohydrates, and triglycerides levels. In addition, increased hiobarbituric acid reactive species, in association with reduced total glutathione and DPPH radical scavenging activity (%) have suggested an imbalance between oxide-reducing agents and antioxidant defense system, induced by pollutant. On the other hand, increased acetylcholinesterase activity has suggested the neurotoxic effect of PE MPs. Finally, PE MPs have accumulated in the larvae, and it may have been a triggering factor for the observed changes. Thus, our study has confirmed the potential of C. quinquefasciatus larvae to act as vector of MPs in different ecosystems and helped improving the knowledge about how PE MPs can affect their development and lead to losses in different ecological functions of this species.
We report three major and confronting environmental issues that have received little attention and require urgent action. First, we review the evidence that future environmental conditions will be far more dangerous than currently believed. The scale of the threats to the biosphere and all its lifeforms — including humanity — is in fact so great that it is difficult to grasp for even well-informed experts. Second, we ask what political or economic system, or leadership, is prepared to handle the predicted disasters, or even capable of such action. Third, this dire situation places an extraordinary responsibility on scientists to speak out candidly and accurately when engaging with government, business, and the public. We especially draw attention to the lack of appreciation of the enormous challenges to creating a sustainable future. The added stresses to human health, wealth, and well-being will perversely diminish our political capacity to mitigate the erosion of ecosystem services on which society depends. The science underlying these issues is strong, but awareness is weak. Without fully appreciating and broadcasting the scale of the problems and the enormity of the solutions required, society will fail to achieve even modest sustainability goals.
Significance
India is the world’s largest fruit producer and second most populous country. Pollinators are therefore important for India’s food security. India also contains 9 of the world’s 10 most polluted cities, but the impact of air pollution on plant and animal systems is largely unknown. We performed a multiyear study in the megacity of Bangalore to correlate the mechanistic effects of air pollution on a major Indian pollinator, the Giant Asian honey bee, Apis dorsata . Wild honey bees and lab-reared Drosophila exposed to air pollution exhibited differences in survival, behavior, heart rate, blood cell count, and/or the expression of genes related to stress, immunity, and metabolism. Our study indicates the urgency for more studies on wild systems to better inform international air quality guidelines.
Although the fates of microplastics (0.1–5 mm in size) and nanoplastics (<100 nm) in marine environments are being increasingly well studied1,2, little is known about the behaviour of nanoplastics in terrestrial environments3,4,5,6, especially agricultural soils⁷. Previous studies have evaluated the consequences of nanoplastic accumulation in aquatic plants, but there is no direct evidence for the internalization of nanoplastics in terrestrial plants. Here, we show that both positively and negatively charged nanoplastics can accumulate in Arabidopsis thaliana. The aggregation promoted by the growth medium and root exudates limited the uptake of amino-modified polystyrene nanoplastics with positive surface charges. Thus, positively charged nanoplastics accumulated at relatively low levels in the root tips, but these nanoplastics induced a higher accumulation of reactive oxygen species and inhibited plant growth and seedling development more strongly than negatively charged sulfonic-acid-modified nanoplastics. By contrast, the negatively charged nanoplastics were observed frequently in the apoplast and xylem. Our findings provide direct evidence that nanoplastics can accumulate in plants, depending on their surface charge. Plant accumulation of nanoplastics can have both direct ecological effects and implications for agricultural sustainability and food safety.
Background:
The insect gut microbiota has been shown to contribute to the host's digestion, detoxification, development, pathogen resistance, and physiology. However, there is poor information about the ranking of these roles. Most of these results were obtained with cultivable bacteria, whereas the bacterial physiology may be different between free-living and midgut-colonizing bacteria. In this study, we provided both proteomic and genomic evidence on the ranking of the roles of gut bacteria by investigating the anal droplets from a weevil, Cryptorhynchus lapathi.
Results:
The gut lumen and the anal droplets showed qualitatively and quantitatively different subsets of bacterial communities. The results of 16S rRNA sequencing showed that the gut lumen is dominated by Proteobacteria and Bacteroidetes, whereas the anal droplets are dominated by Proteobacteria. From the anal droplets, enzymes involved in 31 basic roles that belong to 7 super roles were identified by Q-TOF MS. The cooperation between the weevil and its gut bacteria was determined by reconstructing community pathway maps, which are defined in this study. A score was used to rank the gut bacterial roles. The results from the proteomic data indicate that the most dominant role of gut bacteria is amino acid biosynthesis, followed by protein digestion, energy metabolism, vitamin biosynthesis, lipid digestion, plant secondary metabolite (PSM) degradation, and carbohydrate digestion, while the order from the genomic data is amino acid biosynthesis, vitamin biosynthesis, lipid digestion, energy metabolism, protein digestion, PSM degradation, and carbohydrate digestion. The PCA results showed that the gut bacteria form functional groups from the point of view of either the basic role or super role, and the MFA results showed that there are functional variations among gut bacteria. In addition, the variations between the proteomic and genomic data, analyzed with the HMFA method from the point of view of either the bacterial community or individual bacterial species, are presented.
Conclusion:
The most dominant role of gut bacteria is essential nutrient provisioning, followed by digestion and detoxification. The weevil plays a pioneering role in diet digestion and mainly digests macromolecules into smaller molecules which are then mainly digested by gut bacteria.
Society has become increasingly reliant on plastics since commercial production began in about 1950. Their versatility, stability, light weight, and low production costs have fueled global demand. Most plastics are initially used and discarded on land. Nonetheless, the amount of microplastics in some oceanic compartments is predicted to double by 2030. To solve this global problem, we must understand plastic composition, physical forms, uses, transport, and fragmentation into microplastics (and nanoplastics). Plastic debris/microplastics arise from land disposal, wastewater treatment, tire wear, paint failure, textile washing, and at‐sea losses. Riverine and atmospheric transport, storm water, and disasters facilitate releases. In surface waters plastics/microplastics weather, biofoul, aggregate, and sink, are ingested by organisms and redistributed by currents. Ocean sediments are likely the ultimate destination. Plastics release additives, concentrate environmental contaminants, and serve as substrates for biofilms, including exotic and pathogenic species. Microplastic abundance increases as fragment size decreases, as does the proportion of organisms capable of ingesting them. Particles <20 μm may penetrate cell membranes, exacerbating risks. Exposure can compromise feeding, metabolic processes, reproduction, and behavior. But more investigation is required to draw definitive conclusions. Human ingestion of contaminated seafood and water is a concern. Microplastics indoors present yet uncharacterized risks, magnified by the time we spend inside (>90%) and the abundance of polymeric products therein. Scientific challenges include improving microplastic sampling and characterization approaches, understanding long‐term behavior, additive bioavailability, and organismal and ecosystem health risks. Solutions include improving globally based pollution prevention, developing degradable polymers and additives, and reducing consumption/expanding plastic reuse.
Evidence for global bee population declines has catalyzed a rapidly evolving area of research that aims to identify the factors involved and to effectively assess the status of pollinator populations. The term pollinator health emerged in the literature through efforts to understand causes of bee decline and colony losses, but it lacks a formal definition. In this review, we propose a definition for pollinator health and synthesize the available literature on the application of biomarkers to assess health at the individual, colony, and population levels. We focus on biomarkers in honey bees, a model species, but extrapolate the potential application of these approaches to monitor the health status of wild bee populations. Biomarker-guided health measures can inform beekeeper management decisions, wild bee conservation efforts, and environmental policies. We conclude by addressing challenges to pollinator health from a One Health perspective that emphasizes the interplay between environmental quality and human, animal, and bee health.
Expected final online publication date for the Annual Review of Animal Biosciences, Volume 8 is February 15, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Societal Impact Statement
The global decline in pollinating insect populations has rightly received widespread news coverage as it imperils ecosystem function and human food security. Reversing and addressing this decline is an urgent global priority. However, in many locations we do not know what species are present, how large or small species populations are, or what types of specific resources the populations require. By adopting novel network analyses approaches and by working with monitoring programs, such as Oxford Plan Bee, we may be able to dramatically improve our ability to predict species extinctions and facilitate targeted conservation action to maintain abundant, diverse and stable pollinator communities.
Summary
Pollination is fundamentally important to ecosystem function and human food security. Recent reports of dramatic insect declines, and pollinator decline in particular, have increased public awareness and political motivation to act to protect pollinators. This article maps commonly proposed management interventions onto known drivers of bee decline, and identifies forage and nest site provision as a tractable management intervention that can simultaneously address multiple drivers of decline. However, it is recognized that there are gaps in the knowledge of exactly how much and which types of forage resources are necessary to support wild pollinator populations. A novel network analysis approach based on quantified floral resources and pollination services is proposed, which would illuminate the types and quantities of floral resources and pollinators necessary to maintain a diverse and abundant plant–pollinator community. The approach would also facilitate the prediction of species extinctions in plant–pollinator communities and help target conservation interventions. Finally, Oxford Plan Bee is introduced as a new, citizen‐science‐based project to monitor solitary bee populations, and provide empirical data to validate predictions from the proposed network approach. The over‐arching aim of the described network analysis approach and the Oxford Plan Bee project is to facilitate effective, evidence‐based conservation action to protect pollinators and the plants they pollinate into the future.
While the ecological effects of pesticides have been well studied in honeybees, it is unclear to what extent other anthropogenic contaminants such as air pollution may also negatively affect bee cognition and behaviour. To answer this question, we assessed the impacts of acute exposure to four ecologically relevant concentrations of a common urban air pollutant—diesel generated air pollution on honeybee odour learning and memory using a conditioned proboscis extension response assay. The proportion of bees that successfully learnt odours following direct air pollution exposure was significantly lower in bees exposed to low, medium and high air pollutant concentrations, than in bees exposed to current ambient levels. Furthermore, short- and long-term odour memory was significantly impaired in bees exposed to low medium and high air pollutant concentrations than in bees exposed to current ambient levels. These results demonstrate a clear and direct cognitive cost of air pollution. Given learning and memory play significant roles in foraging, we suggest air pollution will have increasing negative impacts on the ecosystem services bees provide and may add to the current threats such as pesticides, mites and disease affecting colony fitness.
Transitions from animal to wind pollination have occurred repeatedly in flowering plants, driven by structural and biomechanical modifications to flowers. But the initial changes promoting wind pollination are poorly understood, especially those required to release pollen into airflows – the critical first stage of wind pollination.
Using a wind tunnel, we performed a comparative study of pollen release biomechanics in 36 species of animal‐ and wind‐pollinated Thalictrum. We quantified pollination syndromes and stamen natural frequency (fn), a key vibration parameter, to determine if floral traits reliably predicted pollen release probability. We then investigated if pollen release was caused by wind‐induced resonance vibration of stamens.
We detected wind‐induced stamen resonance in 91% of species and a strong effect of stamen acceleration on pollen release, inversely driven by fn. However, unlike fn, pollination syndromes did not reliably predict the probability of pollen release among species.
Our results directly link fn to the capacity of stamens to release pollen by wind and suggest that structural mechanisms reducing fn are likely to be important for initiating transitions from animal to wind pollination. Our inability to predict the probability of pollen release based on pollination syndromes suggests diverse phenotypic trajectories from animal to wind pollination.
Female mosquitoes exploit olfactory, CO2, visual, and thermal cues to locate vertebrate hosts. Male and female mosquitoes also consume floral nectar that provides essential energy for flight and survival. Heretofore, nectar-foraging mosquitoes were thought to be guided solely by floral odorants. Using common tansies, Tanacetum vulgare L., northern house mosquitoes, Culex pipiens L., and yellow fever mosquitoes, Aedes aegpyti (L.), we tested the hypothesis that the entire inflorescence Gestalt of olfactory, CO2 and visual cues is more attractive to mosquitoes than floral odorants alone. In laboratory experiments, we demonstrated that visual and olfactory inflorescence cues in combination attract more mosquitoes than olfactory cues alone. We established that tansies become net producers of CO2 after sunset, and that CO2 enhances the attractiveness of a floral blend comprising 20 synthetic odorants of tansy inflorescences. This blend included nine odorants found in human headspace. The “human-odorant-blend” attracted mosquitoes but was less effective than the entire 20-odorant floral blend. Our data support the hypothesis that the entire inflorescence Gestalt of olfactory, CO2 and visual cues is more attractive to mosquitoes than floral odorants alone. Overlapping cues between plants and vertebrates support the previously postulated concept that haematophagy of mosquitoes may have arisen from phytophagy.
Significance
Increased mortality of honey bee colonies has been attributed to several factors but is not fully understood. The herbicide glyphosate is expected to be innocuous to animals, including bees, because it targets an enzyme only found in plants and microorganisms. However, bees rely on a specialized gut microbiota that benefits growth and provides defense against pathogens. Most bee gut bacteria contain the enzyme targeted by glyphosate, but vary in whether they possess susceptible versions and, correspondingly, in tolerance to glyphosate. Exposing bees to glyphosate alters the bee gut community and increases susceptibility to infection by opportunistic pathogens. Understanding how glyphosate impacts bee gut symbionts and bee health will help elucidate a possible role of this chemical in colony decline.
Over 75% of crop species produce nectar and are dependent on pollinators to achieve maximum seed set, yet little is known about the mechanisms regulating nectar secretion. The phytohormone jasmonic acid (JA) is recognized to be involved in several plant processes including development and defense. JA was also recently shown to positively influence nectar secretion in both floral and extrafloral nectaries. For example, endogenous JA levels peak in flowers just prior to nectar secretion, but the details of how JA regulates nectar secretion have yet to be elucidated. We have found that the octadecanoid pathway does indeed play a role in the production and regulation of floral nectar in Arabidopsis. Null alleles for several JA biosynthesis and response genes had significantly reduced amounts of nectar, as well as altered expression of genes known to be involved in nectar production. We additionally identified crosstalk between the JA and auxin response pathways in nectaries. For example, the nectar-less JA synthesis mutant aos-2 showed no auxin response in nectaries, but both nectar production and the auxin response were restored upon exogenous JA and auxin treatment. Conversely, coi1-1, a JA-Ile-insensitive receptor mutant, displayed no auxin response in nectaries under any circumstance, even in older flowers that produced nectar. Surprisingly, opr3-1, a mutant for 12-oxophytodienoate reductase 3 [an enzyme further down the JA biosynthetic pathway that reduces 12-oxo phytodienoic acid (OPDA)], produced no nectar in newly opened flowers, but did secrete nectar in older flowers. Furthermore, a similar phenotype was observed in coi1-1. Cumulatively, these observations strongly suggest an indispensable role for an octadecanoic acid- and auxin-dependent, but JA- and COI1-dispensible, pathway in regulating nectar production in Arabidopsis.
Although microplastics (MPs) are distributed globally in the marine environment, a great deal of unknowns relating to their ecotoxicological effects on the marine biota remains. Due to their lipophilic nature, microplastics have the potential to adsorb persistent organic pollutants present in contaminated regions, which may increase their detrimental impact once assimilated by organisms. This study investigates the ecotoxicological effects of exposure to low-density polyethylene (LDPE) microplastics (11–13 μm), with and without adsorbed contaminants (benzo[a]pyrene—BaP and perfluorooctane sulfonic acid—PFOS), in the peppery furrow shell clam, Scrobicularia plana. Environmentally relevant concentrations of contaminants (BaP−16.87 ± 0.22 μg g⁻¹ and PFOS−70.22 ± 12.41 μg g⁻¹) were adsorbed to microplastics to evaluate the potential role of plastic particles as a source of chemical contamination once ingested. S. plana were exposed to microplastics, at a concentration of 1 mg L⁻¹, in a water-sediment exposure setup for 14 days. Clams were sampled at the beginning of the experiment (day 0) and after 3, 7, and 14 days. BaP accumulation, in whole clam tissues, was analyzed. A multi-biomarker assessment was conducted in the gills, digestive gland, and haemolymph of clams to clarify the effects of exposure. This included the quantification of antioxidant (superoxide dismutase, catalase, glutathione peroxidase) and biotransformation (glutathione-S-transferases) enzyme activities, oxidative damage (lipid peroxidation levels), genotoxicity (single and double strand DNA breaks), and neurotoxicity (acetylcholinesterase activity). Results suggest a potential mechanical injury of gills caused by ingestion of microplastics that may also affect the analyzed biomarkers. The digestive gland seems less affected by mechanical damage caused by virgin microplastic exposure, with the MPs-adsorbed BaP and PFOS exerting a negative influence over the assessed biomarkers in this tissue.
Microplastics (plastics <5 mm diameter) are at the forefront of current environmental pollution research, however, little is known about the degradation of microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical micro-plastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.
The effect of a pollutant on the base of the food web can have knock-on effects for trophic structure and ecosystem functioning. In this study we assess the effect of microplastic exposure on juveniles of a planktivorous fish (Acanthochromis polyacanthus), a species that is widespread and abundant on Indo-Pacific coral reefs. Under five different plastic concentration treatments, with plastics the same size as the natural food particles (mean 2mm diameter), there was no significant effect of plastic exposure on fish growth, body condition or behaviour. The amount of plastics found in the gastro-intestinal (GI) tract was low, with a range of one to eight particles remaining in the gut of individual fish at the end of a 6-week plastic-exposure period, suggesting that these fish are able to detect and avoid ingesting microplastics in this size range. However, in a second experiment the number of plastics in the GI tract vastly increased when plastic particle size was reduced to approximately one quarter the size of the food particles, with a maximum of 2102 small (< 300μm diameter) particles present in the gut of individual fish after a 1-week plastic exposure period. Under conditions where food was replaced by plastic, there was a negative effect on the growth and body condition of the fish. These results suggest plastics could become more of a problem as they break up into smaller size classes, and that environmental changes that lead to a decrease in plankton concentrations combined with microplastic presence is likely have a greater influence on fish populations than microplastic presence alone.
Most plant-pollinator interactions occur during specific periods during the day. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission and petal opening, in a daily rhythmic fashion. However, less is known about how the internal timing mechanisms (the circadian clocks) of plants and animals influence their daily interactions. We examine the role of the circadian clock in modulating the interaction between Petunia and one of its pollinators, the hawkmoth Manduca sexta. We find that desynchronization of the Petunia circadian clock affects moth visitation preference for Petunia flowers. Similarly, moths with circadian time aligned to plants show stronger flower-foraging activities than moths that lack this alignment. Moth locomotor activity is circadian clock-regulated, although it is also strongly repressed by light. Moths show a time-dependent burst increase in flight activity during subjective night. In addition, moth antennal responsiveness to the floral scent compounds exhibits a 24-hour rhythm in both continuous light and dark conditions. This study highlights the importance of the circadian clocks in both plants and animals as a crucial factor in initiating specialized plant-pollinator relationships.
Micro(nano)plastics (MNPs) are categorized as emerging persistent pollutants that occur widely in various ecosystems. However, their impacts on terrestrial plants (particularly crops) are poorly understood. Given the persistence and widespread distribution of MNPs in the soil, it is necessary to recognize their potential impacts on terrestrial plants. This paper highlights the uptake, translocation, and phytotoxicity of MNPs in terrestrial plants. Due to their small size and high adsorption capacity, MNPs can adhere to the surfaces of seeds and roots, and thus inhibit seed germination, root elongation, and absorption of water and nutrients, and ultimately inhibit plant growth. Microplastics (MPs), especially nanoplastics (NPs), can be absorbed by roots, and be translocated to stems, leaves, and fruits. The adherence and accumulation of MNPs can induce oxidative stress, cytotoxicity, and genotoxicity in plants, leading to a series of changes in plant growth, mineral nutrition, photosynthesis, toxic accumulation, and metabolites in plants tissues. Overall, the phytotoxicity of MNPs varies dependent on their polymer type, size, dose, and shape, plant tolerance, and exposure conditions. Of particular importance is that the accumulation of MNPs and subsequent damage in plants may further affect crop productivity, and food safety and quality, causing potential health risks. Finally, knowledge gaps and future research priorities are discussed.
Micro- (MPs) and nano-plastics (NPs) have become emerging pollutants in the environment. Their wide distribution and capacity as a vector of hazardous materials threaten various organisms. Honeybees have been used as bioindicators for pollutants as their gut microbiota offers advantages for addressing how it alters the host health and exploring the processes of environmental pollutants affecting gut community dynamics. In this study, the effects of plastic particles of different sizes on honeybees' health were investigated. Oral exposure to polystyrene (PS) particles with a diameter of 100 nm significantly decreased the whole-body weight and survival rate of honeybees and induced intestinal dysplasia. As the increase of the feeding time from Day 0 to Day 15, the MPs moved to and accumulated in the rectum, where most bee gut symbionts colonized. Scanning electron microscope (SEM) observation showed that 100-nm PS particles adhered to the germination pore of pollen, while 1- and 10-μm PS particles were attached by gut bacteria. We found that 100-nm PS treatment decreased the relative abundance of Lactobacillus and Bifidobacterium in the guts. Correspondingly, PS treatment stimulated immune inhibitory genes and depressed genes related to detoxification and energy balance. Furthermore, 100-nm PS treated honeybees became more susceptible to the pathogenic Hafnia alvei, leading to a five-times higher mortality rate. These results indicated the adverse impacts of NPs on honeybees, which extends our knowledge regarding the emerging health risks of plastic debris, especially at the nanoscale.
Microplastics (MPs) are ubiquitous contaminants. In recent decades, the hazardous impacts of MPs on the environment have raised significant concern. However, little attention has been focused on the interaction between MPs and plants in terrestrial agroecosystems. This study aims to investigate the effects of polyethylene microspheres (PE-MS) on the germination, morphology, and metabolism of barley (Hordeum vulgare L.), cucumber (Cucumis sativus L.), and tomato (Solanum lycopersicum L.). Specifically, seeds were soaked in PE-MS solutions at three concentrations (10, 100, and 1000 mg L⁻¹), while control seeds were treated with distilled water. After five days, the morphological parameters of barley (i.e., shoot and root biomass, length, and average diameter) were significantly affected by PE-MS treatment, even at the lowest concentration, without a dose dependency. On the other hand, the effect of PE-MS on the morphological parameters of cucumber and tomato was evident only at the highest concentration (1000 mg L⁻¹). PE-MS also induced metabolomic reprogramming of shoots and roots in all three plant species. There was a downregulation of fatty acids and secondary metabolites (except in tomato shoots). In addition, the response of amino acids and hormones was highly heterogeneous among species and plant parts. In particular, the response of metabolites changed within species among different plant parts.
In conclusion, we found a strong influence of MS-PE on the metabolic profile of the three plant species and a positive priming of seedling growth, especially in barley, where all the morphological parameters considered were significantly improved. Further investigations are needed to fully understand the mechanisms underlying MP-plant interactions, especially in the long term.
The degradable plastic poly(butylene adipate-co-terephthalate) (PBAT) is considered a potential replacement for low-density polyethylene (LDPE) as the main component of mulch film. However, it is not clear whether PBAT is harmful to the plant-soil system. Thus, we determined the effects of LDPE microplastics (LDPE-MPs) and PBAT microplastics (PBAT-MPs) on the growth of Arabidopsis. The inhibitory effect of PBAT-MPs was greater than that of LDPE-MPs on the growth of Arabidopsis. Transcriptome analysis showed that PBAT-MPs severely disrupted the photosynthetic system of Arabidopsis and increased the expression levels of genes in drug transport-related pathways. PBAT-MPs increased the relative abundances of Bradyrhizobium, Hydrogenophaga, and Arthrobacter in the bulk soil and rhizosphere soil. The abundances of Variovorax, Flavobacterium, and Microbacterium increased in the plant root zone only under PBAT-MPs. Functional prediction analysis suggested that microorganisms in the soil and plant root zone could degrade xenobiotics. Furthermore, the degradation products from PBAT comprising adipic acid, terephthalic acid, and butanediol were more toxic than PBAT-MPs. Our findings demonstrate that PBAT-MPs may be degraded by microorganisms to produce chemicals that are highly toxic to plants. Thus, biodegradable plastics may pose a great risk to the environment.
Microplastics (MPs) are considered emerging and persistent pollutants, although most of the research has been conducted on marine environments. Declines in honeybee populations have been reported globally, and recently, microplastic pollution has been considered a possible cause of this. Thus, we aimed to determine acute toxicity of polyester fibers and their effects on foraging behavior in honeybees. To test this, we conducted an oral acute toxicity bioassay, testing the effect of MPs on individual honeybees, and we studied the foraging behavior of honeybees when exposed to food and water containing MPs. We observed no mortality in honeybees fed with sucrose solution containing 100 mg MP/L after 24 and 48 h. Upon bee dissection of the digestive tract, we found 1.27 ± 1.5 fibers per bee, showing a mean (±SE) of 0.92 (±1.14) and 0.32 (±0.70) in their gut and crop respectively. The length of these microfibers ranged between 0.05 and 1.24 mm with a mean (±SE) of 0.42 (±0.25) mm. Although we did not find any preference or avoidance of MPs when presented in sucrose solutions and water; bees consumed MP-free solutions faster than solutions with 10 and 100 mg MPs/L. This might be due to changes in the viscosity of the solutions containing plastic and has implications for the impact of microplastic pollution on insects. Results suggest that MPS do not pose a threat to honeybees in the short term, based on the lack of acute mortality. However, bee foraging behavior does not prevent them from ingesting MPs present in water or resources which potentially might cause lethal long-term effects of MPs.
Biodegradation of plastic polymers by plastic-eating insects such as the greater wax moth (Galleria mellonella) might be promising for reducing plastic pollution, but direct in vivo evidence along with the related metabolic pathways and role of gut microbiota require further investigation. In this study, we investigated the in vivo degradation process, underlying potential metabolic pathways, and involvement of the gut microbiota in polystyrene (PS) biodegradation via enforcing injection of G. mellonella larvae (Tianjin, China) with PS microbeads (0.5 mg/larva; Mn: 540 and Mw: 550) and general-purpose PS powders (2.5 mg/larva; Mn: 95,600 and Mw: 217,000). The results indicated that the PS microplastics were depolymerized and completely digested independent of gut microbiota in G. mellonella although the metabolism could be enhanced by gut microbiota. Based on comparative metabolomic and liquid chromatography analyses, we proposed two potential metabolic pathways of PS in the intestine of G. mellonella larvae: the styrene oxide–phenylacetaldehyde and 4-methylphenol–4-hydroxybenzaldehyde–4-hydroxybenzoate pathways. These results suggest that the enzymes of G. mellonella are responsible for the efficient biodegradation of PS. Further study is needed to identify these enzymes and investigate the underlying catalytic mechanisms.
At present, the uptake and accumulation of nanoplastics by plants have raised particular concerns. However, molecular mechanisms underlying nanoplastic phytotoxicity are still vague and insufficient. To address this scientific gap, we analyzed the transcriptome response of hydroponically grown wheat (Triticum aestivum L.) to polystyrene nanoplastics (PSNPs) (100 nm) by integrating the differentially expressed gene analysis (DEGA) and the weighted gene correlation network analysis (WGCNA). PSNPs could significantly shape the gene expression patterns of wheat in a tissue-specific manner. Four candidate modules and corresponding hub genes associated with plant traits were identified using WGCNA. PSNPs significantly altered carbon metabolism, amino acid biosynthesis, mitogen-activated protein kinase (MAPK) signaling pathway-plant, plant hormone signal transduction, and plant-pathogen interaction Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. In addition, some Gene Ontology (GO) terms associated with the metal ion transport were further screened. These findings shed new light on the phytotoxic mechanism and environmental implication behind the interaction of nanoplastics and crop plants, and advance our understanding of the potential adverse effect induced by the presence of nanoplastics in agricultural systems.
Microplastic accumulation in agricultural soils can stress plants and affects quality of the products. Current research on the effects of microplastics on plants is not consistent and the underlying mechanisms are yet unknown. Here, the molecular mechanisms of the stress response were investigated via metabolomic and transcriptomic analyses of rice Oryza sativa L. II Y900 and XS123 under the exposure of polystyrene microplastics (PS-MPs) in a field study. Distinct responses were obtained in these two rice subspecies, showing decreased head rice yield by 10.62% in Y900 and increase by 6.35% in XS123.The metabolomics results showed that PS-MPs exposure inhibited 29.63% of the substance accumulation-related metabolic pathways and 43.25% of the energy expenditure-related metabolic pathways in the Y900 grains; however, these related pathways were promoted in the XS123 grains. The transcriptomics results indicated that the expression of genes encoding proteins involved in the tricarboxylic acid cycle in the Y900 grains was inhibited, but it was enhanced in the XS123 grains. The XS123 subspecies could response against microplastic exposure stress through the metabolite accumulation and energy expenditure pathways, while the Y900 could not. The results provide insight into the perturbation of rice grains in farmlands with microplastics contamination.
Microplastics, as a new type of pollution, have attracted global attention and have become a research focus in recent years. Given the small size of microplastics, they can be ingested by many organisms. In addition, microplastics can enter the human body through the food chain. So, the potential dangers of microplastics can't be ignored. This study took Drosophila as a model organism to delve the physiological effects of polyethylene terephthalate microplastics (PET-MPs). Here, we reported that the higher concentration of PET-MPs was, the more obvious the effect became. The amount of oviposition decreased in female flies exposed, indicating that microplastics affected reproduction. PET-MPs caused the decrease of triglyceride and glucose content in male flies, as well as the decrease of starvation resistance, suggesting the effect of microplastics on energy metabolism. In addition, the 24-hour spontaneous activity of flies exposed to PET-MPs increased significantly. The experimental results can help understand the potential impact of microplastics on physiology.
Microplastics and nanoplastics (MPs and NPs, respectively) are major contaminants of environmental concern
due to their potentially detrimental effects on aquatic and terrestrial ecosystems. However, little is known about
their potential toxicity in terrestrial organisms. Here, we used the model insect silkworm (Bombyx mori) to
evaluate the potential hazardous effects of acute exposure (72 h) to polystyrene (PS) MPs and NPs at physiological,
molecular, and biochemical levels as well as their impact on pathogen infection. Our results revealed no
significant changes in larval body mass or survival. Nevertheless, exposure led to significant alterations in the
expression of immunity-related genes (Cecropin A, Lysozyme, SOD, and GST) and antioxidant-mediated protective
response (SOD, GST, and CAT enzymes) which differed in the PS-MP and PS-NP groups. Interestingly, PS-MPs
induced a stronger immune response (higher expressions of Lysozyme, SOD, and GST genes along with
increased activities of SOD, GST, and CAT enzymes) while the PS-NP response was more that of an inhibitory
nature (decreased SOD activity and expression). As a result, upon infection with the natural pathogen Serratia
marcescens Bm1, the PS-MP-exposed individuals survived the infection better whereas, PS-NP-exposed individuals
exhibited significantly higher mortality. Thus, we infer that PS-MPs/NPs present ecological toxicity,
which is closely related to their size, and that their exposure may render the organisms vulnerable or confer
resistance to pathogen infections and ecotoxicants. Given the suitability of silkworm as a model organism, this
study may promote its application for further investigation of the mechanism of adverse outcome pathways and
in studies on bio-nano interactions.
Microplastic contamination is not only a pressing environmental concern in oceans, but also terrestrial ecosystems. However, little is known about its potential impacts on pollinators. Here, we reported the effects of 25 μm-diameter spherical polystyrene microplastics (PS-MPs) alone or in combination with the antibiotic tetracycline on honey bees (Apis mellifera L.) in the laboratory. We noticed that PS-MPs exposure for 14 d had sublethal effects, with low mortalities (up to 1.6 %) across three different treatments (0.5, 5, and 50 mg/L) and no changes to the body weight gains compared to the control bees. Nevertheless, PS-MPs exposure led to significant decreases in the α-diversity of bees’ gut microbiota accompanied by changes to the core microbial population structure. Additionally, PS-MPs lead to alterations in the expression of antioxidative (Cat), detoxification (CypQ1 and GstS3), and immune system-related genes (Domeless, Hopscotch, and Symplekin) in guts. More interestingly, we observed that PS-MPs accumulated and degraded inside of the hindgut and interacted with gut bacteria. The depletion of the normal gut microbiota using tetracycline dramatically increased the lethality of microplastics. These results provide a resource for future research on microplastic-microbiome interactions in other insects and also shed light on understanding the potential effects of microplastics in terrestrial ecosystems.
The interactions of microplastics (MPs) with other chemicals and the range of outcomes are of great importance to enhance understanding of their environmental impacts and health risks. Cadmium (Cd) and cadmium compounds are widely used as pigments and stabilizers in plastics, but they readily leach out. Here we addressed the impacts of MPs, Cd, and their joint exposure in a tractable Drosophila melanogaster model. We show that exposure to MPs lead to extensive particle size depended gut damage early in life and an enhancement of Cd-induced inhibition of locomotor-behavioral function in adult flies. In addition, we show that Cd exposure induces epigenetic gene silencing via position-effect variegation (PEV) in somatic tissues that was dramatically enhanced by co-exposure with MPs. The results indicate that MPs can aggravate the toxicity of other environmental contaminants and induce adverse effects across a range of diverse outcomes in a tractable and widely used model organism. These observations raise the prospects of using Drosophila as a tool for the rapid assessment of MP-mediated toxicity.
Microplastics pollution in farmlands has become a major concern. However, few studies have assessed the effects of microplastics on higher plants. In this study, we investigated the influence of polystyrene nanoplastics (PSNPs, 50 mg L⁻¹), with four different particle sizes (100, 300, 500, and 700 nm), on the physiological and biochemical indexes of cucumber leaves. The biomass of cucumber plants significantly decreased after exposure to 300 nm PSNPs. Similarly, the chlorophyll a, chlorophyll b, soluble sugar, carotenoid, and proline content, as well as the fluorescence of cucumber leaves were significantly reduced by 100 nm PSNPs. Malondialdehyde, proline, peroxidase gene expression and enzyme activity, and hydrogen peroxide content significantly increased in cucumber leaves exposed to 700 nm PSNPs. In addition, increasing PSNPs particle size led to decreased relative expression levels and activities of the major antioxidant enzymes superoxide dismutase and catalase, while vitamin C and soluble protein content significantly increased. Overall, our results indicated that PSNPs affect the photosynthetic, antioxidant, and sugar metabolism systems of cucumber leaves, with the latter clearly affecting the total biomass of cucumber plants. The benzene ring resulting from the degradation of PSNPs in cucumber leaves may be the main factor affecting chlorophyll metabolism and sugar metabolism. Our findings provide a scientific basis for the risk assessment of PSNPs exposure in soil-plant systems.
In this study, for the first time, acute and chronic toxicity caused by four different kinds of microplastics: polypropylene (PP), polyethylene (PE), polyvinylchloride (PVC), and a commercial mixture (PE + PVC) on Lepidium sativum were evaluated. Parameters considered were: i) biometric parameters (e.g. percentage inhibition of seed germination, plant height, leaf number and fresh biomass productions); and ii) oxidative stress (e.g. levels of hydrogen peroxide, glutathione, and ascorbic acid). On plants exposed to chronic stress chlorophylls, carotenoids, aminolaevulinic acid, and proline productions were, also, evaluated. PVC resulted the most toxic than other plastic materials tested. This study represents the first paper highlighting microplastics are able to produce oxidative burst in tested plants and could represent an important starting point for future researches on biochemical effects of microplastic in terrestrial environments such as agroecosystems.
Pollination is the transfer of pollen grains from the stamens to the stigma, an essential requirement of sexual reproduction in flowering plants. Cross-pollination increases genetic diversity and is favored by selection in the majority of situations. Flowering plants have evolved a wide variety of traits that influence pollination success, including those involved in optimization of self-pollination, attraction of animal pollinators, and the effective use of wind pollination. In this review we discuss our current understanding of the molecular basis of the development and production of these various traits. We conclude that recent integration of molecular developmental studies with population genetic approaches is improving our understanding of how selection acts on key floral traits in taxonomically diverse species, and that further work in nonmodel systems promises to provide exciting insights in the years to come.
Expected final online publication date for the Annual Review of Plant Biology, Volume 71 is April 29, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Environmental pollution caused by plastics has become a public health problem. However, the effect of microplastics on gut microbiota, inflammation development and their underlying mechanisms are not well characterized. In the present study, we assessed the effect of exposure to different amounts of polyethylene microplastics (6, 60, and 600 μg/day for 5 consecutive weeks) in a C57BL/6 mice model. Treatment with a high concentration of microplastics increased the numbers of gut microbial species, bacterial abundance, and flora diversity. Feeding groups showed a significant increase in Staphylococcus abundance alongside a significant decrease in Parabacteroides abundance, as compared to the blank (untreated) group. In addition, serum levels of interleukin-1α in all feeding groups were significantly greater than that in the blank group. Of note, treatment with microplastics decreased the percentage of Th17 and Treg cells among CD4+ cells, while no significant difference was observed between the blank and treatment groups with respect to the Th17/Treg cell ratio. The intestine (colon and duodenum) of mice fed high-concentration microplastics showed obvious inflammation and higher TLR4, AP-1, and IRF5 expression. Thus, polyethylene microplastics can induce intestinal dysbacteriosis and inflammation, which provides a theoretical basis for the prevention and treatment of microplastics-related diseases.
Bumble bees ( Bombus) are unusually important pollinators, with approximately 260 wild species native to all biogeographic regions except Africa, Australia, and New Zealand. As they are vitally important in natural ecosystems and to agricultural food production globally, the increase in reports of declining distribution and abundance over the past decade has led to an explosion of interest in bumble bee population decline. We summarize data on the threat status of wild bumble bee species across biogeographic regions, underscoring regions lacking assessment data. Focusing on data-rich studies, we also synthesize recent research on potential causes of population declines. There is evidence that habitat loss, changing climate, pathogen transmission, invasion of nonnative species, and pesticides, operating individually and in combination, negatively impact bumble bee health, and that effects may depend on species and locality. We distinguish between correlational and causal results, underscoring the importance of expanding experimental research beyond the study of two commercially available species to identify causal factors affecting the diversity of wild species.
Expected final online publication date for the Annual Review of Entomology, Volume 65 is January 7, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Plant vibrations is a wide subject that covers topics ranging from the swaying of trees under wind to elastic waves made by an insect on a leaf to communicate with its neighbors. For this reason, the state of the art is somehow fragmented over several communities. This review aims at giving a general overview of the main results and challenges in plant vibrations. Several scales are considered, from the very small and local, in leaves or fruits, to large canopies of many plants.
Different shapes of microplastics are widely detected in the environment and organisms and most of them remain in the gut. However, the influences of shapes on the bioaccumulation and toxicity of microplastics in the gut are largely unknown. Three shapes (bead, fragment, and fiber) of microplastics of comparable size in one dimension were prepared to exposure to zebrafish. The accumulation and toxicities of microplastics in the gut were detected. Shape-dependent accumulation in the gut was observed with the order of fibers (8.0 μg/mg) > fragments (1.7 μg/mg) > beads (0.5 μg/mg). The accumulation of microplastics caused multiple toxic effects in fish intestine, including mucosal damage, and increased permeability, inflammation and metabolism disruption. Based on these toxic effects, microplastic fibers resulted in more severe intestinal toxicity than microplastic fragments and beads did. Furthermore, microplastics also induced gut microbiota dysbiosis and specific bacteria alterations, which will provide novel insights into the potential mechanism of microplastics causing intestinal toxicities in fish. Our results also suggested that shape-depended effects should not be ignored in the health risk assessment of microplastics.
Biodiversity of insects is threatened worldwide. Here, we present a comprehensive review of 73 historical reports of insect declines from across the globe, and systematically assess the underlying drivers. Our work reveals dramatic rates of decline that may lead to the extinction of 40% of the world's insect species over the next few decades. In terrestrial ecosystems, Lepidoptera, Hymenoptera and dung beetles (Coleoptera) appear to be the taxa most affected, whereas four major aquatic taxa (Odonata, Plecoptera, Trichoptera and Ephemeroptera) have already lost a considerable proportion of species. Affected insect groups not only include specialists that occupy particular ecological niches, but also many common and generalist species. Concurrently, the abundance of a small number of species is increasing; these are all adaptable, generalist species that are occupying the vacant niches left by the ones declining. Among aquatic insects, habitat and dietary generalists, and pollutant-tolerant species are replacing the large biodiversity losses experienced in waters within agricultural and urban settings. The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change. The latter factor is particularly important in tropical regions, but only affects a minority of species in colder climes and mountain settings of temperate zones. A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.
Bees-including solitary, social, wild, and managed species-are key pollinators of flowering plant species, including nearly three-quarters of global food crops. Their ecological importance, coupled with increased annual losses of managed honey bees and declines in populations of key wild species, has focused attention on the factors that adversely affect bee health, including viral pathogens. Genomic approaches have dramatically expanded understanding of the diversity of viruses that infect bees, the complexity of their transmission routes-including intergenus transmission-and the diversity of strategies bees have evolved to combat virus infections, with RNA-mediated responses playing a prominent role. Moreover, the impacts of viruses on their hosts are exacerbated by the other major stressors bee populations face, including parasites, poor nutrition, and exposure to chemicals. Unraveling the complex relationships between viruses and their bee hosts will lead to improved understanding of viral ecology and management strategies that support better bee health.
Flower morphology results from the interaction of an established genetic program, the influence of external forces induced by pollination systems, and physical forces acting before, during and after initiation. Floral ontogeny, as the process of development from a meristem to a fully developed flower, can be approached either from a historical perspective, as a "recapitulation of the phylogeny" mainly explained as a process of genetic mutations through time, or from a physico-dynamic perspective, where time, spatial pressures, and growth processes are determining factors in creating the floral morphospace. The first (historical) perspective clarifies how flower morphology is the result of development over time, where evolutionary changes are only possible using building blocks that are available at a certain stage in the developmental history. Flowers are regulated by genetically determined constraints and development clarifies specific transitions between different floral morphs. These constraints are the result of inherent mutations or are induced by the interaction of flowers with pollinators. The second (physico-dynamic) perspective explains how changes in the physical environment of apical meristems create shifts in ontogeny and this is reflected in the morphospace of flowers. Changes in morphology are mainly induced by shifts in space, caused by the time of initiation (heterochrony), pressure of organs, and alterations of the size of the floral meristem, and these operate independently or in parallel with genetic factors. A number of examples demonstrate this interaction and its importance in the establishment of different floral forms. Both perspectives are complementary and should be considered in the understanding of factors regulating floral development. It is suggested that floral evolution is the result of alternating bursts of physical constraints and genetic stabilization processes following each other in succession. Future research needs to combine these different perspectives in understanding the evolution of floral systems and their diversification.
Microplastic (MP) has become a concerning global environmental problem. It is toxic to aquatic organisms and can spread through the food chain to ultimately pose a threat to humans. In the environment, MP can interact with microbes and act as a microbial habitat. However, effects of polystyrene MP on the gut microbiota in mammals remain unclear. Here, male mice were exposed to two different sizes of polystyrene MP for 5 weeks to explore its effect. We observed that oral exposure to 1000 μg/L of 0.5 and 50 μm polystyrene MP decreased the body, liver and lipid weights in mice. Mucus secretion in the gut decreased in both sizes of polystyrene MP-treated groups. Regarding the gut microbiota, at the phylum level, polystyrene MP exposure decreased the relative abundances of Firmicutes and α-Proteobacteria in the feces. Furthermore, high throughput sequencing of the V3-V4 region of the 16S rRNA gene revealed significant changes in the richness and diversity of the gut microbiota in the cecums of polystyrene MP-treated mice. At the genus level, a total of 6 and 8 types of bacteria changed in the 0.5 and 50 μm polystyrene MP-treated groups, respectively. Furthermore, an operational taxonomic unit (OTU) analysis identified that 310 and 160 gut microbes were changed in the 0.5 and 50 μm polystyrene MP-treated groups, respectively. In addition, the hepatic triglyceride (TG) and total cholesterol (TCH) levels decreased in both 1000 μg/L 0.5 and 50 μm polystyrene MP-treated groups. Correspondingly, the relative mRNA levels of some key genes related to lipogenesis and TG synthesis decreased in the liver and epididymal fat. These results indicated that polystyrene MP could modify the gut microbiota composition and induce hepatic lipid disorder in mice; while the mouse is a common mammal model, consequently, the health risks of MP to animals should not be ignored.
