米バイオテクノロジー企業のモンサントは、RNA干渉(RNAi  *)を利用した農薬スプレーを開発していると発表しました。RNAiによって、害虫や雑草がもつ有害な遺伝子のスイッチだけをオフにできるとのことです。同社は、このスプレーのよる作用は一時的で、生物の遺伝的変化を招くことはないとし、遺伝子組み替え作物の代替になりうるともしています。記事はMIT Technology Reviewに掲載されました。この件についての海外専門家コメントをお送りします。



MIT Technology Review article: 


Dr. Jeffrey Scott

Professor, Department of Entomology, Cornell University




"The single biggest problem with conventional insecticides is their effects on non-target organisms. Using RNA interference to kill pests through sprays of double stranded RNA (dsRNA) has the potential to be species specific. This individual targeting can be achieved because genes vary enough between different species that specific dsRNA could only affect the desired pest. However, targeting single species is not guaranteed. For example, in a recent paper we showed that a spray of dsRNA from a house fly could kill Colorado Potato Beetles.

"In some cases, conventional insecticides are used because they kill multiple insect pests.  Thus, an insecticide that targets only one species has lots of benefits, but might not be cost effective. Then there is the issue that insects always find a way to evolve resistance, and harnessing RNAi will be no different.  The relative speed with which resistance will happen is a wide open question.

"Currently, using dsRNA sprays is limited to insects that eat the leaf.  Insects like aphids that consume fluids from the leaf seem much less affected. Some species are just refractory to this technology and this includes several economically important Lepidoptera (caterpillars).  There may be ways to use this technology against aphids and other refractory species, but we are only in the early stages.

"There is a big gap from discovery to field application and cost is often a big  Monsanto is reputed to be in the third year of field trials with their product, so they must think it has big potential, but I am not sure how Monsanto will protect their intellectual property.  There are some interesting issues associated with the technology because as far as I know the gene can’t be patented."


Dr. Allison Snow, Professor of Evolution

Ecology, and Organismal Biology, Ohio State University




“This is a great article because the author brings together a lot of disparate and new information to make a compelling argument.  RNAi sprays are so new and proprietary that most academic ecologists like me know very little about them.  It may take awhile before biotech companies figure out which RNAi sprays are going to work well enough to be commercially viable, but the field is moving quickly.

“Like GMOs, these genetic sprays will need to be evaluated for health and environmental effects on a case-by-case basis.  It doesn’t make sense to group them together and conclude that all of them are either safe or risky.  Nonetheless, it’s important to have public discussions about safety to learn more about the scale, dosage, biological effects, and persistence of new products that are in the R&D pipeline, like Monsanto’s Biodirect RNAi sprays.  As noted in the article, the Environmental Protection Agency’s expert panel didn’t express concerns about effects of the sprays on human health, but they lacked enough information to evaluate to potential for unwanted environmental effects, including harm to non-target insects.  This information gap will need to be addressed
“In comparison to plants with genetically engineered traits, which are passed on to their descendants, the use of RNAi sprays would avoid concerns about the long-term persistence of unwanted synthetic genes in breeding lines, organic food, exported agricultural products, and related plant species that can cross-pollinate with transgenic crops.  It is impossible to completely control the movement of transgenic seeds and pollen in most agricultural systems.  In contrast, if environmental problems should arise with genetic sprays, their use could be discontinued.  From this standpoint, RNAi sprays would be an improvement over the use of genome editing and other types of genetic engineering that alter an organism’s genes and cannot be contained after commercialization.”





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