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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - dsRNAEnvFate (Environmental fate of double stranded RNA (dsRNA) from RNA interference crop protection technology in agricultural systems: A systematic assessment of dsRNA hydrolysis, adsorption, and photolysis)

Teaser

Summary

Next-generation genetically modified (GM) crops seek to use RNA interference (RNAi) to protect crops through the expression of double-stranded RNA (dsRNA) biopesticides. Upon ingestion of the dsRNA biopesticide by a pest insect, the biosynthesis of targeted proteins by the insect is prevented, resulting in insect death. Some dsRNA biopesticides are rapidly approaching commercialization. However, limited information is available regarding the processes that govern the fate of dsRNA biopesticides after release from GM crops to surrounding environmental matrices (e.g., agricultural soils), resulting in uncertainty in exposure analysis required for environmental risk assessment of RNAi crops. To reduce these uncertainties, we have developed novel experimental approaches to evaluate the transport and transformation of dsRNA biopesticides in environmental matrices including soils, sediments and surface water bodies. Experiments investigated the impact of microbial and enzymatic degradation, abiotic transformation, and adsorption to particle surfaces on dsRNA fate in these environmental matrices. Overall, this work advances our understanding of the stability and distribution of dsRNA biopesticides in environmental matrices and informs exposure analysis required in environmental risk assessment models.Â The contribution will highlight the application of new experimental approaches to overcome methodological and conceptual challenges associated with studying the environmental fate of dsRNA biopesticides and other biomacromolecular pesticides produced by GM crops. By enabling research into the fate of these biomacromolecular pesticides, we can better evaluate potential environmental and health impacts associated with the use of next-generation GM crops protected by dsRNA and other biopesticides.

Work performed

Ongoing research seeks to characterize dsRNA adsorption and transformation in environmental systems. Dr. Parker has developed novel techniques to investigate dsRNA adsorption and degradation and is now applying these techniques to characterize dsRNA fate in agricultural soils.

The first set of experiments relates to dsRNA adsorption and transport. Under the supervision of Dr. Parker, two Masterâ€™s students at ETH investigated dsRNA adsorption to surfaces representing major environmental sorbents. Overall, their findings indicate the dsRNA adsorbs strongly to positively charged surfaces in the environment such as iron oxides. Using column studies, the students investigated how adsorption of dsRNA to iron oxides impacts the transport of dsRNA in the subsurface. This work was successfully submitted as two MS theses to ETH Zurich in June and September 2017, respectively. Currently, Dr. Parker is supervising a PhD student who is using a technique called quartz crystal microbalance with dissipation monitoring to investigate the real-time dsRNA adsorption to and desorption from model surfaces. Work included in the MS theses and in ongoing work by the PhD student will be incorporated in forthcoming peer-reviewed publications.

The second set of experiments relates to dsRNA adsorption and degradation in agricultural soils. To enable these experiments, Dr. Parker synthesized radioactively-labeled dsRNA and developed procedures to investigate the fate of dsRNA in soil microcosm experiments. These results show that attachment of dsRNA molecules to soil particulates is an important process affecting the fate of dsRNA in soils. To date, these results have been presented at the European Cooperation in Science and Technology (COST) Action â€œ1st iPlanta Conference: Creating a Plant RNAi Research Networkâ€ (presented on February 15th 2017, Rome, Italy), the American Chemical Society (ACS) National Meeting (presented on April 6th 2017, San Francisco, CA), the Association of Environmental Engineering & Science Professors meeting (presented on April 6th 2017, San Francisco, CA), and the ACS National Meeting (presented on March 21st 2018, New Orleans, LA). Currently, Dr. Parker is preparing these results into a manuscript to be submitted for peer review.

Final results

\"Dr. Parker has engaged with stakeholders invested in RNAi crop technology and its risk assessment. Dr. Parker presented her work at the COST RNAi Research Network, which was attended by researchers developing RNAi technology as well as risk assessors from the European Food Safety Authority responsible for the regulation of RNAi crops in Europe. At the ACS Meeting in San Francisco, Dr. Parker presented her work in a session organized by the California Department of Pesticide Regulation, whose representatives may be engaged in dsRNA biopesticide regulation in the near future. Finally, she has been in communication with the United States Department of Agriculture Biotechnology Risk Assessment Program about research needs in RNAi crop risk assessment. In May 2018, she will be presenting a poster at the USDA Biotechnology Risk Assessment Program summit on this topic.

In addition, Dr. Parker has been actively working to train the next generation of scientists. In addition to supervising two Masterâ€™s students in their theses on the topic of dsRNA adsorption to surfaces, Dr. Parker mentored two other Masterâ€™s students during their writing and presentation of formal term papers on environmental pollutants in agriculture. Along with two other instructors, Dr. Parker served as a lecturer for the course â€œCase Studies in Environment and Health\"\". Finally, Dr. Parker served on the organizing committee for a team of twenty ETH Zurich researchers to prepare exhibits for the ETH Zurich outreach event â€œScientificaâ€.
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