Daphnia magna negatively affected by chronic exposure to purified Cry-toxins

A review on the identification of transgenic oilseeds and oils

Transgenic technology can increase the quantity and quality of vegetable oils worldwide. However, people are skeptical about the safety of transgenic oil-bearing crops and the oils they produce. In order to protect consumers' rights and avoid transgenic oils being adulterated or labeled as nontransgenic oils, the transgenic detection technology of oilseeds and oils needs careful consideration. This paper first summarized the current research status of transgenic technologies implemented at oil-bearing crops. Then, an inspection process was proposed to detect a large number of samples to be the subject rapidly, and various inspection strategies for transgenic oilseeds and oils were summarized according to the process sequence. The detection indicators included oil content, fatty acid, triglyceride, tocopherol, and nucleic acid. The detection technologies involved chromatography, spectroscopy, nuclear magnetic resonance, and polymerase chain reaction. It is hoped that this article can provide crucial technical reference and support for staff engaging in the supervision of transgenic food and for researchers developing fast and efficient monitoring methods in the future.

Review on the ecotoxicological impacts of plastic pollution on the freshwater invertebrate Daphnia

The environmental impacts of plastic pollution have recently attracted universal attention, especially in the aquatic environment. However, research has mostly been focused on marine ecosystems, even though freshwater ecosystems are equally if not more polluted by plastics. In addition, the mechanism and extent to which plastic pollution affects aquatic biota and the rates of transfer to organisms through food webs eventually reaching humans are poorly understood, especially considering leaching hazardous chemicals. Several studies have demonstrated extreme toxicity in freshwater organisms such Daphnia. When such keystone species are affected by ambient pollution, entire food webs are destabilized and biodiversity is threatened. The unremitting increase in plastic contaminants in freshwater environments would cause impairments in ecosystem functions and structure, leading to various kinds of negative ecological consequences. As various studies have reported the effects on daphnids, a consolidation of this literature is critical to discuss the limitations and knowledge gaps and to evaluate the risk posed to the aquatic environment. This review was undertaken due to the evident need to evaluate this threat. The aims were to provide a meaningful overview of the literature relevant to the potential impact of plastic pollution and associated contaminants on freshwater daphnids as primary consumers. A critical evaluation of research gaps and perspectives is conducted to provide a comprehensive risk assessment of microplastic as a hazard to aquatic environments. We outlined the challenges and limitations to microplastic research in hampering better-focused investigations that could support the development of new plastic materials and/or establishment of new regulations.

Novel Field-Based Protein Detection Method Using Light Transmission Spectroscopy and Antibody Functionalized Gold Nanoparticles

Protein detection is a universal tool critical to many applications in medicine, agriculture, and biotechnology. We developed a novel protein detection method combining light transmission spectroscopy and particle-size analysis of gold nanospheres monovalently functionalized with polyclonal antibodies and applied it to an emerging challenge for such technologies─the monitoring of environmental proteins (eProteins) present in natural aquatic systems. These are an underreported source of pollution and include the pseudopersistent Cry toxins that enter aquatic ecosystems from surrounding genetically engineered crops. The assay is capable of detecting proteins in complex matrices, such as water samples collected in the field, making it a competitive assay for eProtein detection. It is sensitive, reaching 1.25 ng mL^-1, and we demonstrate its application to the detection of Cry1Ab from subsurface tile-drain and streamwater samples from agricultural waterways. The assay can also be quickly adapted for other protein detection applications in the future.

Addressing the challenges of non-target feeding studies with genetically engineered plant material - stacked Bt maize and Daphnia magna

Previous studies reported adverse effects of genetically engineered maize that produces insecticidal Cry proteins from Bacillus thuringiensis (Bt) on the water flea Daphnia magna. In the current study, effects of flour, leaves, or pollen from stacked Bt maize that contains six Bt proteins (SmartStax) in two plant backgrounds on life table parameters of D. magna were investigated. Adverse effects were observed for Bt maize flour, originating from different production fields and years, but not for leaves or pollen, produced from plants grown concurrently in a glasshouse. Because leaves contained eight to ten times more Cry protein than flour, the effects of the flour were probably not caused by the Cry proteins, but by compositional differences between the plant backgrounds. Furthermore, considering the natural range of variation in the response of D. magna to conventional maize lines, the observed effects of Bt maize flour were unlikely to be of biological relevance. Our study demonstrates how Cry protein effects can be separated from plant background effects in non-target studies using Bt plant material as the test substance and how detected effects can be judged for their biological relevance.

Fate of Environmental Proteins (eProteins) from Genetically Engineered Crops in Streams is Controlled by Water pH and Ecosystem Metabolism

Environmental proteins (eProteins), such as Cry proteins associated with genetically engineered (GE) organisms, are present in ecosystems worldwide, but only rarely reach concentrations with detectable ecosystem-level impacts. Despite their ubiquity, the degradation and fate of Cry and other eProteins are mostly unknown. Here, we report the results of an experiment where we added Cry proteins leached from GE Bt maize to a suite of 19 recirculating experimental streams. We found that Cry exhibited a biphasic degradation with an initial phase of rapid and variable degradation within 1 h, followed by a slow and steady phase of degradation with traces of protein persisting after 48 h. The initial degradation was correlated with heterotrophic respiration and water column dissolved oxygen, confirming a previously documented association with stream metabolism. However, protein degradation persisted even with no biofilm and was faster at a more acidic pH, suggesting that water chemistry is also a critical factor in both degradation and subsequent detection. We suggest that Cry, as well as other eProteins, will have a rapid degradation caused by denaturation of proteins and pH changes, which confirms that the detection of Cry proteins in natural streams must be the result of steady and consistent leaching into the environment.

MicroRNAs in Daphnia magna identified and characterized by deep sequencing, genome mapping and manual curation

MicroRNAs (miRNAs) are small non-coding RNAs that function in RNA silencing and post-transcriptional regulation of gene expression in most organisms. The water flea, Daphnia magna is a key model to study phenotypic, physiological and genomic responses to environmental cues and miRNAs can potentially mediate these responses. By using deep sequencing, genome mapping and manual curations, we have characterised the miRNAome of D. magna. We identified 66 conserved miRNAs and 13 novel miRNAs; all of these were found in the three studied life stages of D. magna (juveniles, subadults, adults), but with variation in expression levels between stages. Forty-one of the miRNAs were clustered into 13 genome clusters also present in the D. pulex genome. Most miRNAs contained sequence variants (isomiRs). The highest expressed isomiRs were 3′ template variants with one nucleotide deletion or 3′ non-template variants with addition of A or U at the 3′ end. We also identified offset RNAs (moRs) and loop RNAs (loRs). Our work extends the base for further work on all species (miRNA, isomiRs, moRNAs, loRNAs) of the miRNAome of Daphnia as biomarkers in response to chemical substances and environment cues, and underline age dependency.

Acute and chronic effects of polystyrene microplastics on juvenile and adult Daphnia magna

We investigate the distribution and effects of polystyrene microplastic (MP) particles in exposure experiments with the ecotoxicology model organism Daphnia magna. The aim was to investigate the short and long-term toxicity of MP at different concentrations. To achieve this goal, the effects of 6 μm commercially available polystyrene beads on two different life-stages of D. magna: < 24 h old juveniles and 9 days old adults was assessed. The following end points in test animals were measured: (1) survival, (2) growth, (3) individual and population fecundity, (4) age at maturation and (5) body size of newborn offspring. These response variables were followed in two acute and two chronic experiments. The acute experiments showed that MP is not acutely toxic to D. magna within 48 h, but cause added mortality within 120 h. The juveniles were about 50% more sensitive than the adults tested. In life-cycle experiments testing chronic exposure to MP, again, animals exposed as juveniles at relatively high concentrations, i.e. > 30 μg ml^-1 showed higher sensitivity. We observed slightly increased mortality, reduced growth and stimulation of early reproduction at the cost of later reproduction. Animals exposed after reaching adulthood did not show increased mortality and showed a stimulation response with higher reproductive rates than the control group. However, both the growth rate of mother animals and the body size of newborn declined with increasing dose of MP. We conclude that these effects indicate a role of MP in mechanical interaction/interference with the animal on the level of feeding (clogging filtering functions), digestion (gut filled with plastic particles), and/or other animal behavior. The study also illustrates how MP with slow break-down rates may accumulate in the environment and enter the food-chain as obstructing non-food particles in filter-feeding organisms.

Roundup®, but Not Roundup-Ready® Corn, Increases Mortality of Drosophila melanogaster

Genetically modified foods have become pervasive in diets of people living in the US. By far the most common genetically modified foods either tolerate herbicide application (HT) or produce endogenous insecticide (Bt). To determine whether these toxicological effects result from genetic modification per se, or from the increase in herbicide or insecticide residues present on the food, we exposed fruit flies, Drosophila melanogaster, to food containing HT corn that had been sprayed with the glyphosate-based herbicide Roundup®, HT corn that had not been sprayed with Roundup®, or Roundup® in a variety of known glyphosate concentrations and formulations. While neither lifespan nor reproductive behaviors were affected by HT corn, addition of Roundup® increased mortality with an LC50 of 7.1 g/L for males and 11.4 g/L for females after 2 days of exposure. Given the many genetic tools available, Drosophila are an excellent model system for future studies about genetic and biochemical mechanisms of glyphosate toxicity.

Effects of straw leachates from Cry1C-expressing transgenic rice on the development and reproduction of Daphnia magna

The transgenic rice line T1C-19 provides high resistance to lepidopteran pests because of the synthesis of the Bacillus thuringiensis (Bt) insecticidal protein Cry1C. It thus shows good prospect for commercial planting in China. Species of Cladocera, an order of aquatic arthropods commonly found in aquatic ecosystems such as rice paddies, might be exposed to the insecticidal protein released from Bt-transgenic rice-straw residues. For the study reported herein, we used Daphnia magna (water flea) as a representative of Cladocera to evaluate whether aquatic arthropods are adversely affected when exposed to Bt rice-straw leachates. We exposed D. magna to M4 medium containing various volume percentages of medium that had been incubated with T1C-19 rice straw or rice straw from its non-transformed near-isoline Minghui 63 (MH63) for 21 days. Compared with pure M4 medium (control), the fitness and developmental and reproduction parameters of D. magna decreased significantly when exposed to rice-straw leachates; conversely, no significant differences between the T1C-19 and MH63 rice-straw leachate treatments were observed, indicating that the Bt rice straw leachate did not adversely affect this non-target species.

Impact of genetically modified organisms on aquatic environments: Review of available data for the risk assessment

The aquatic environment is strongly connected to the surrounding agricultural landscapes, which regularly serve as sources of stressors such as agrochemicals. Genetically modified crops, which are cultivated on a large scale in many countries, may also act as stressors. Despite the commercial use of genetically modified organisms (GMOs) for over 20years, their impact on the aquatic environment came into focus only 10years ago. We present the status quo of the available scientific data in order to provide an input for informed aquatic risk assessment of GMOs. We could identify only 39 publications, including 84 studies, dealing with GMOs in the aquatic environment, and our analysis shows substantial knowledge gaps. The available information is restricted to a small number of crop plants, traits, events, and test organisms. The analysis of effect studies reveals that only a narrow range of organisms has been tested and that studies on combinatorial actions of stressors are virtually absent. The analysis of fate studies shows that many aspects, such as the fate of leached toxins, degradation of plant material, and distribution of crop residues in the aquatic habitat, are insufficiently investigated. Together with these research needs, we identify standardization of test methods as an issue of high priority, both for research and risk assessment needed for GMO regulation.

Safety Assessment of Bacillus thuringiensis Insecticidal Proteins Cry1C and Cry2A with a Zebrafish Embryotoxicity Test

As a result of the large-scale planting of transgenic Bacillus thuringiensis (Bt) crops, fish would be exposed to freely soluble Bt insecticidal protein(s) that are released from Bt crop tissues into adjacent bodies of water or by way of direct feeding on deposited plant material. To assess the safety of two Bt proteins Cry1C and Cry2A to fish, we used zebrafish as a representative species and exposed their embryos to 0.1, 1, and 10 mg/L of the two Cry proteins until 132 h post-fertilization and then several developmental, biochemical, and molecular parameters were evaluated. Chlorpyrifos (CPF), a known toxicant to aquatic organisms, was used as a positive control. Although CPF exposure resulted in significant developmental, biochemical, and molecular changes in the zebrafish embryos, there were almost no significant differences after Cry1C or Cry2A exposure. Thus, we conclude that zebrafish embryos are not sensitive to Cry1C and Cry2A insecticidal proteins at test concentrations.

Safety of Bacillus thuringiensis Cry1C protein for Daphnia magna based on different functional traits

Cry1C is a Bacillus thuringiensis (Bt) insecticidal protein and it can be produced by transgenic rice lines developed in China. Cladocera species are common aquatic arthropods that may be exposed to insecticidal proteins produced in Bt-transgenic plants through ingestion of pollen or crop residues in water. As the cladoceran Daphnia magna plays an important role in the aquatic food chain, it is important to assess the possible effects of Bt crops to this species. To evaluate the safety of the Cry1C protein for D. magna, individuals were exposed to different concentrations of purified Cry1C protein in M4 medium for 21 days. Potassium dichromate (K₂Cr₂O₇), a known toxicant to D. magna, was added to M4 medium as a positive control treatment, and pure M4 medium was used as a negative control. Our results show that developmental, reproductive, and biochemical parameters of D. magna were not significantly different between Cry1C and negative control treatments but were significantly inhibited by the positive control. We thus conclude that D. magna is insensitive to Cry1C.

Isolation of a peptide from Ph.D.-C7C phage display library for detection of Cry1Ab

Traditional ELISA methods of using animal immunity yield antibodies for detection Cry toxin. Not only is this incredibly harmful to the animals, but is also time-intensive. Here we developed a simple method to yield the recognition element. Using a critical selection strategy and immunoassay we confirmed a clone from the Ph.D-C7C phage library, which has displayed the most interesting Cry1Ab-binding characteristics examined in this study (Fig. 1). The current study indicates that isolating peptide is an alternative method for the preparation of a recognition element, and that the developed assay is a potentially useful tool for detecting Cry1Ab.

Criticism of EFSA's scientific opinion on combinatorial effects of 'stacked' GM plants

Recent genetically modified plants tend to include both insect resistance and herbicide tolerance traits. Some of these 'stacked' GM plants have multiple Cry-toxins expressed as well as tolerance to several herbicides. This means that non-target organisms in the environment (biodiversity) will be co-exposed to multiple stressors simultaneously. A similar co-exposure may happen to consumers through chemical residues in the food chain. EFSA, the responsible unit for minimizing risk of harm in European food chains, has expressed its scientific interest in combinatorial effects. However, when new data showed how two Cry-toxins acted in combination (added toxicity), and that the same Cry-toxins showed combinatorial effects when co-exposed with Roundup (Bøhn et al., 2016), EFSA dismissed these new peer-reviewed results. In effect, EFSA claimed that combinatorial effects are not relevant for itself. EFSA was justifying this by referring to a policy question, and by making invalid assumptions, which could have been checked directly with the lead-author. With such approach, EFSA may miss the opportunity to improve its environmental and health risk assessment of toxins and pesticides in the food chain. Failure to follow its own published requests for combinatorial effects research, may also risk jeopardizing EFSA's scientific and public reputation.

Annual post-market environmental monitoring (PMEM) report on the cultivation of genetically modified maize MON 810 in 2015 from Monsanto Europe S.A

Following a request from the European Commission, the Panel on Genetically Modified Organisms of the European Food Safety Authority (GMO Panel) assessed the annual post-market environmental monitoring (PMEM) report for the 2015 growing season of the Cry1Ab-expressing maize event MON 810 provided by Monsanto Europe S.A. The GMO Panel concludes that the insect resistance monitoring data submitted to EFSA do not indicate a decrease in susceptibility of field Iberian populations of corn borers to the Cry1Ab protein during the 2015 season. However, since the methodology for insect resistance monitoring remained unchanged compared to previous PMEM reports, the GMO Panel reiterates its previous recommendations on resistance monitoring to provide sufficient detection sensitivity. Although the farmer alert system to report complaints about product performance could complement the information obtained from the laboratory bioassays, the GMO Panel is currently not in a position to appraise its usefulness, and therefore encourages the consent holder to provide more information on this complementary resistance monitoring tool. The data on general surveillance (GS) do not indicate any unanticipated adverse effects on human and animal health or the environment arising from the cultivation of maize MON 810. The GMO Panel reiterates its previous recommendations on the analysis of farmer questionnaires, and advises the consent holder to provide more detailed information on the conducting and reporting of the literature search in future annual PMEM reports. Moreover, the GMO Panel encourages relevant parties to continue developing a methodological framework to use existing networks in the broader context of environmental monitoring. The GMO Panel concludes that the case-specific monitoring (CSM) and GS activities of maize MON 810 as carried out by the consent holder do not provide evidence that would invalidate previous GMO Panel evaluations on the safety of maize MON 810.

In plastico: laboratory material newness affects growth and reproduction of Daphnia magna reared in 50-ml polypropylene tubes

Plastic laboratory materials are found to affect vital parameters of the waterflea Daphnia magna. The main responsible factor is defined as “newness” of the materials. Juvenile D. magna were raised individually in; a) new laboratory-standard 50 ml polypropylene tubes, and; b) identical tubes which had been washed and aerated for several weeks. Newness had significant effects on growth and fecundity of D. magna. New tubes caused delayed maturation, reduced reproduction and reduced growth when compared to washed and re-used tubes of the same commercial brand. The findings indicate that newness of tubes has inhibiting or toxic effects on D. magna. Often laboratory plastics are intended for single-use due to sterility demands. Newness might be an important confounding factor in research results and should not be disregarded. Disposable plastic utensils may come with a seemingly ignored cost and induce adverse effects in biological test-organisms and systems. The presented findings accentuate continued need for general awareness concerning confounding factors stemming from material laboratory environment. Based on the present findings the authors suggest that plastics intended for use in sensitive research may need to be washed and aerated prior to use.

Possible health impacts of Bt toxins and residues from spraying with complementary herbicides in genetically engineered soybeans and risk assessment as performed by the European Food Safety Authority EFSA

BACKGROUND

MON89788 was the first genetically engineered soybean worldwide to express a Bt toxin. Under the brand name Intacta, Monsanto subsequently engineered a stacked trait soybean using MON89788 and MON87701-this stacked soybean expresses an insecticidal toxin and is, in addition, tolerant to glyphosate. After undergoing risk assessment by the European Food Safety Authority (EFSA), the stacked event was authorised for import into the EU in June 2012, including for use in food and feed. This review discusses the health risks associated with Bt toxins present in these genetically engineered plants and the residues left from spraying with the complementary herbicide.

RESULTS

We have compared the opinion published by EFSA [1] with findings from other publications in the scientific literature. It is evident that there are several issues that EFSA did not consider in detail and which will need further assessment: (1) There are potential combinatorial effects between plant components and other impact factors that might enhance toxicity. (2) It is known that Bt toxins have immunogenic properties; since soybeans naturally contain many allergens, these immunogenic properties raise specific questions. (3) Fully evaluated and reliable protocols for measuring the Bt concentration in the plants are needed, in addition to a comprehensive set of data on gene expression under varying environmental conditions. (4) Specific attention should be paid to the herbicide residues and their interaction with Bt toxins.

CONCLUSIONS

The case of the Intacta soybeans highlights several regulatory problems with Bt soybean plants in the EU. Moreover, many of the issues raised also concern other genetically engineered plants that express insecticidal proteins, or are engineered to be resistant to herbicides, or have those two types of traits combined in stacked events. It remains a matter of debate whether the standards currently applied by the risk assessor, EFSA, and the risk manager, the EU Commission, meet the standards for risk analysis defined in EU regulations such as 1829/2003 and Directive 2001/18. While this publication cannot provide a final conclusion, it allows the development of some robust hypotheses that should be investigated further before such plants can be considered to be safe for health and the environment. In general, the concept of comparative risk assessment needs some major revision. Priority should be given to developing more targeted approaches. As shown in the case of Intacta, these approaches should include: (i) systematic investigation of interactions between the plant genome and environmental stressors as well as their impact on gene expression and plant composition; (ii) detailed investigations of the toxicity of Bt toxins; (iii) assessment of combinatorial effects taking into account long-term effects and the residues from spraying with complementary herbicides; (iv) investigation into the impact on the immune and hormonal systems and (v) investigation of the impact on the intestinal microbiome after consumption. Further and in general, stacked events displaying a high degree of complexity due to possible interactions should not undergo a lower level of risk assessment than the parental plants.

Interactions between Bt crops and aquatic ecosystems: A review

The term Bt crops collectively refers to crops that have been genetically modified to include a gene (or genes) sourced from Bacillus thuringiensis (Bt) bacteria. These genes confer the ability to produce proteins toxic to certain insect pests. The interaction between Bt crops and adjacent aquatic ecosystems has received limited attention in research and risk assessment, despite the fact that some Bt crops have been in commercial use for 20 yr. Reports of effects on aquatic organisms such as Daphnia magna, Elliptio complanata, and Chironomus dilutus suggest that some aquatic species may be negatively affected, whereas other reports suggest that the decreased use of insecticides precipitated by Bt crops may benefit aquatic communities. The present study reviews the literature regarding entry routes and exposure pathways by which aquatic organisms may be exposed to Bt crop material, as well as feeding trials and field surveys that have investigated the effects of Bt-expressing plant material on such organisms. The present review also discusses how Bt crop development has moved past single-gene events, toward multigene stacked varieties that often contain herbicide resistance genes in addition to multiple Bt genes, and how their use (in conjunction with co-technology such as glyphosate/Roundup) may impact and interact with aquatic ecosystems. Lastly, suggestions for further research in this field are provided. Environ Toxicol Chem 2016;35:2891-2902. © 2016 SETAC.