Researchers find gene-silencing nanoparticles may put end to pesky summer pest

July 19, 2010

Summer just wouldn't be complete without mosquitoes nipping at exposed skin. Or would it? Research conducted by a Kansas State University team may help solve a problem that scientists and pest controllers have been itching to for years.

Kun Yan Zhu, professor of entomology, and teammates Xin Zhang, graduate student in entomology from China, and Jianzhen Zhang, a visiting scientist from Shanxi University, China, investigated using nanoparticles to deliver double-stranded ribonucleic acid, dsRNA -- a molecule capable of specifically triggering gene silencing -- into mosquito larvae through their food. By silencing particular genes, Zhu said the dsRNA may kill the developing or make them more susceptible to pesticides.

Gene silencing triggered by dsRNA or , , is known as RNA interference, or RNAi.

"RNAi is a specific and effective approach for loss of function studies in virtually all eukaryotic organisms," Zhu said. Eukaryotic organisms have cells that contain a nucleus within which is carried and can therefore be manipulated. Almost all animals, plants and fungi are eukaryotes.

Once RNAi is triggered, it destroys the , or mRNA, of a particular gene. This prevents the translation of the gene into its product, silencing it. In the case of Zhu's research, RNAi was used to silence genes responsible for the production of chitin, the principle constituent of the exoskeleton in insects, crustaceans and arachnids.

"Since our RNAi is focused on chitin synthesis, the dsRNA that is delivered into the mosquito larvae can basically block the production of chitin," Zhu said.

Though the silencing is not yet 100 percent effective in their study, Zhu said it does leave the mosquito's body with less ability to combat insecticides, which must penetrate the mosquito's exoskeleton. If the gene, called chitin synthase, could be completely silenced, the mosquitoes may die without the use of pesticides because the chitin biosynthesis pathway would be blocked, Zhu said.

Zhu theorized using nanoparticles to deliver dsRNA to mosquito larvae might work because of the low success of manually injecting larvae with dsRNA. Mosquito larvae live in water but because dsRNA quickly dissipates in water, it can't be directly added to the larvae's food source. Zhu's group discovered that using nanoparticles assembled from dsRNA facilitates their ingestion by because the nanoparticles don't dissolve in water. Zhu said the nanoparticles may also stabilize the dsRNA in water.

"Now insects will have a much greater likelihood of getting these nanoparticles containing the dsRNA into their gut through feeding," Zhu said.

Potentially, bait containing dsRNA-based nanoparticles could be developed for insect control, Zhu said.

"Because we can select specific genes for silencing, and the nanoparticles are formed from chitosan -- a virtually non-toxic and biodegradable polymer -- this pest control technology could target specific pest species while being environmentally friendly," he said.

Mosquitoes were chosen, Zhu said, because of the abundant research on them as human disease vectors. Other insects, though, can have their genes silenced. Zhu and his collaborators also have investigated gene silencing in the European corn borer and in grasshoppers, a major insect pest in China. Nanoparticles did not have to be used because grasshoppers and European corn borers are not aquatic. However, nanoparticle-based RNAi may facilitate the studies on the functions of new genes.

Explore further: Targeted nanoparticles incorporating siRNA offer promise for cancer treatment

More information: The team's paper, "Chitosan/double-stranded RNA nanoparticle-mediated RNA interference to silence chitin synthase genes through larval feeding in African malaria mosquito (Anopheles gambiae)," was recently accepted by the journal, Insect Molecular Biology. It has been published online in advance of print.

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not rated yet Jul 19, 2010
"RNAi is a specific and effective approach for loss of function studies in virtually all eukaryotic organisms,"

Does anyone else think this could go horribly, horribly wrong? I can't find anything in the article that states how this is targeted only to mosquitoes.
not rated yet Jul 19, 2010
anyone think that food chain is going to be hit pretty hard when 10's of billions of moquitoes dissapear a few weeks after they start using this stuff?
not rated yet Jul 19, 2010
Not only that, but are we sure that mosquitoes are in some other yet non-understood method helpful to us and other organisms? What if for some reason we gain some genetic information through their injections that has yet to be discovered. We should stop screwing with billions of years of trial and error.
not rated yet Jul 19, 2010
If somebody kill them all it will be just great, the nobel price would be a small price for this person.
But this gene thing....i dont think this is the most efective way to do this.
not rated yet Jul 19, 2010
There are there a large number of creatures that find mosquito larvae a useful food source. Add to that the fact that, as hbar_squared pionts out, the targeting of RNAi specifically to mosquitos is very weak and the scope for something going horribly wrong is very high. Yes, a lot of people hate bugs and at this time of year I hate mosquitos and those black flies that kept landing on my salad an hour ago. On the other hand how do the plants get pollenated? How does the soil become aerated and fertile? How does dead organic matter become recycled? Only by the effort of insects.
1 / 5 (1) Jul 19, 2010
Just think of the possibilities - if a technology can be developed to deliver RNA-carrying nanoparticles via an aerial spray, designed to shut off a gene like, one that enables the human body to absorb oxygen, well, what a way to exterminate millions or billions of humans without bombs or physical destruction. Perhaps in the near future, our own technological advancement will lead to human extinction.
5 / 5 (1) Jul 19, 2010
we have something like that it is called cianide, it is not as cool as the RNA stuff but it is really efective...
not rated yet Jul 21, 2010
First, almost any alternative food sources can be found for almost any food chain.Mankind and viruses,bacteria and animals have interfered in the food chains around the globe.It's called mutation and migration.The ecosystem moves and evolves.Even the Spotted Owls began mating with other owls.
Second,if someone says black flies have a useful function,it is someone who has not encountered them.I feel that way about many studies of pest control.It's very nice to sitback in a nice safe lab and control the little beasties.But, if you happen to have children,parents,animals,crops,and other responsibilities in your life you might not be so objective.
This inventor got money to find out how to control these pests.Do many critics fail to get a grants?
This always reminds me of the infighting at NIH and the Defense Department. It's vicious and unbending because there's never enough cash.

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