Team:Cardiff Wales/Applied Design

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Cardiff iGEM 2018

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Applied Design

Communication with stakeholders

As part of our Human practices we decided to communicate with potential stakeholders if our system were to be deployed into the real world. Most communication was either via email or at our outreach events.

Via our survey we asked the public what their views and opinions of genetic modification were, and found a surprisingly positive result overall, though a large proportion of respondents were either under 20 years old or had a scientific education.

However, even at our the 3G conference outreach event, aimed at retirees, and at the talk given to a Welsh Sixth Form, there was still an overwhelming majority that supported genetic modification of crops. We found that a very common concern was the risk of off-target effects. One lady at the 3G event, Miriam Knight, informed us of a previously unknown interaction between wasps, aphids, and honeybees. This concern caused us to look into the potential off-target effects of our project on honeybees and other non-target organisms, including aphid predators that may come in contact with our siRNAs. We communicated with the Welsh Bee Keepers Association (WBKA) to get more details about the interactions between aphids and honeybees, and found that the honeybees actually eat the honeydew that aphids secrete from the plants. This meant that the honeybees could be eating small amounts of our siRNAs that were also secreted from the aphids that feed on our modified crops. To address the concerns raised by the public and the WBKA, we decided to bioinformatically analyse the potential toxicity of our siRNAs on any organism that would likely come in contact with our siRNAs, including aphid predators, honeybees, and humans who would eat the crops. Where possible, we analysed the transcriptomes of organisms as only the transcribed regions of the genomes are at risk from siRNA targetting. This was only possible for humans and honeybees, but we found there was no risk to either. There were small numbers of hits against the genomic sequences of the aphid predators, but there is a strong likelihood that the regions in which our siRNAs have homology are not transcribed. Nevertheless, we cannot rule this out until better genome annotation is released on these organisms, and so have to assume that aphid predators might be at risk.

We then communicated to an Agronomist, John Harrington, who works alongside Bayer and NIAB, and met up with him. He discussed the potential usefulness of our project, deciding that the project would definitely be favourable relative to standard methods of control, which naturally harm non-target organisms anyway. John called a friend from NIAB to ask what proportion of crops are treated with aphid insecticides each year, in which the response was around 90-95% of crop area.

Finally, we decided to contact the Welsh Environment minister, Hannah Blythyn, to discuss how our project and genetic modification of crops would be viewed politically. We aim to meet with a representative to discuss this in November.

How does it compare to standard?

According to the Pesticide Research Institute (PRI), traditional methods to control aphid populations include biological pest control, shown to be highly effective by our model, and the use of potentially very harmful insecticides including organophosphates, N-Methyl carbamates, neonicotinoids, pyrethroids, and several others⁽¹⁾. These are high-impact chemical insecticides that can often be broad-spectrum, killing many off-target insects as well as the pest. As with all pesticides, overuse of insecticides that have common mechanisms of action can cause cross-resistance to develop, which has already been shown in Australia by the GRDC, where aphid resistance to commercial insecticides is now widespread⁽²⁾. Low impact, non-persistent insecticides such as insecticidal soaps and oils, but these only combat aphids that are present at the time of application, and so need to be re-applied very regularly, making them unfeasible for those working in the agricultural industry on large plots of land^(1,3). Some of these pesticides have been proven to be severely damaging to bee populations, and potentially harmful to humans too^(1,4). Finally, these chemical pesticides can also leave areas unaffected, as unless they are systemic, chemicals as sprays don't affect areas shaded by leaves⁽⁵⁾.

Our method of aphid control is favourable as we have analysed the potential toxicity which has shown us that there should be no direct negative impacts on either bee populations or on human health, according to current transcriptomic data. It has also shown that there may be slight risks to aphid predators, but these are minor relative to some of the currently used pesticides. In addition, to our knowledge there are no known cases of insect resistance to RNAi methods of control, probably because RNAi is a natural system that exists within the insects. Lastly, the siRNA is systemic and in the vasculature, so spreads around the plant. This means that the farmer would never need to apply the insecticide as it is produced constitutively by the plant, and needs not worry about regions of the plant being unaffected. This means that provided our siRNAs are toxic to the aphids, and can control populations, they should be vastly more reliable than the currently employed methods.

In terms of price, this would depend on EU laws. Currently, transgenic plants must be sterile so as to prevent introgression into wild-type populations, or spread of the crop and/or transgene. This means that GM crops need to be bought as seeds every season, making them more expensive than conventional crops which can simply be propagated again. On the other hand, they would not need to have the insecticides applied regularly, making them cheaper in this sense. Researchers have shown that aphid insecticide use costs between $23 and $58 USD per hectare of soybean⁽⁶⁾. Compare this to the cost of GM soybean, which has been reported to be as low as $2 USD per hectare, up to $65 USD per hectare⁽⁷⁾. Taking into account that aphid pesticides are not used exclusively, but GM crops can have stacked traits providing multiple resistances to many pests, it's clear to see that the GM option could easily be cheaper. However, there is not yet enough data about crops with RNAi transgenes and their cost analysis to definitively say that our method would be cheaper that using aphid insecticides, but the prices are at least similar.

Future potential

The application of our insecticide would depend on cost analysis, toxicity, and European laws. In the future, we would need to test the toxicity of our RNAi constructs via our toxicity assays, outlined on our design page. More about the political aspect of our application should become resolved when meeting with a Welsh Government representative. For now, we can say that at least ecologically, our RNAi insecticide (and likely other RNAi insecticides) are superior to current chemical ones.

References

(1) - PRI (2018). Aphid Control. [Online] Pesticide Research Institute. Available at: https://www.pesticideresearch.com/site/pri-resource-centers/pest-mgmt/pest-mgmt-bulletins/aphid-control/ [Accessed 3 Oct. 2018].

(2) - Clarry, S. (2013). Insecticide resistance increasing in aphids. [Online] Grains Research and Development Corporation. Available at: "https://grdc.com.au/resources-and-publications/groundcover/ground-cover-issue-106-sept-oct-2013/insecticide-resistance-increasing-in-aphids [Accessed 23 Sep. 2018].

(3) - Flint, M. (2018). Aphids Management Guidelines--UC IPM [Online]. Available at: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html [Accessed: 3 October 2018].

(4) - Nicolopoulou-Stamati, P., Maipas, S., Kotampasi, C., Stamatis, P. and Hens, L. (2016). Chemical Pesticides and Human Health: The Urgent Need for a New Concept in Agriculture. Frontiers in Public Health 4.

(5) - CANNA UK (2018). Aphids - Pests & Diseases | CANNA UK. [online] Canna-uk.com. Available at: http://www.canna-uk.com/aphids-pests-diseases [Accessed 20 Sep. 2018].

(6) - Johnson, K., O'Neal, M., Ragsdale, D., Difonzo, C., Swinton, S., Dixon, P. and Potter, B. et al. (2009). Probability of Cost-Effective Management of Soybean Aphid (Hemiptera: Aphididae) in North America. Journal of Economic Entomology 102:2101-2108.

(7) - Brookes, G. and Barfoot, P. (2014). Economic impact of GM crops. GM Crops & Food 5:65-75.