RNA insecticides

The bacterium is a "Trojan horse"

Maxim Russo, Polit.<url> based on Entomology Today: Bacteria Can Be Used for RNA Interference in Insects

A new method of influencing insects is proposed, in which bacteria inhabiting the digestive system of these insects act as a tool. The method promises to be effective for a number of species, including those dangerous to humans.

The method is based on RNA interference, a mechanism used by organisms to regulate gene activity. Regulation occurs due to the fact that special molecules – small interfering RNAs - are attached to the matrix RNAs that the cell uses as a "matrix" for protein synthesis. As a result, matrix RNA cannot start the synthesis of the corresponding protein in the ribosome, and its production in the cell decreases. Although the gene continues to work in the cell nucleus, synthesizing matrix RNA, it actually turns off.

The mechanism of RNA interference in a number of insect species has been studied for some time, and scientists have a desire to use this phenomenon to influence insects. But the problem was the delivery of the corresponding small interfering RNAs into the insect's body. Now it turned out that bacteria can help in this matter. Scientists from Swansea University in Wales called this technology symbionto-mediated RNA interference. Symbiont bacteria from the intestines of insects transmit to them the necessary RNA chains that "turn off" the production of certain proteins in their body.

The method was tested on two types of insects. The first is the kissing bug (Rhodnius prolixus). The subfamily of triatomic, or kissing, bugs includes more than a hundred species that prefer to bite in the area of mucous membranes, for example, in the human lips, for which they were given this name. The species Rhodnius prolixus lives in Central and South America and serves as a carrier of Chagas disease.

Rhodnius prolixus (snapshot from Wikimedia Commons)

The second participant in the tests was the Western flower thrips (Frankliniella occidentalis), a small insect only about a millimeter long that punctures the leaves of plants and feeds on their cellular juice. Western flower thrips can feed on dozens of plant species, from carnations and chrysanthemums to burdock and cucumbers. A native of California, he has been widely distributed in Europe, Australia, China and South America since the 1980s. Plants affected by it at best reduce yields, and with severe infection they die. In addition, Western flower thrips carries a number of viral diseases affecting plants. At the same time, trips managed to develop resistance to most pesticides.

In kissing bugs, researchers decided to turn off the genes responsible for the ability to reproduce. For Western flower thrips, genes were selected whose incorrect operation should have led to the death of the insect at the larval stage. The corresponding small interfering DNA was delivered to the body of bedbugs and thrips with the help of intestinal bacteria. As a result, the fertility of kissing bugs decreased by 100%, and the larval mortality of thrips reached 60%.

Scientists believe that symbionto-mediated RNA interference will be applicable to a wide range of insect species, both carriers of dangerous diseases and agricultural pests. In case of further development of the method, it will be possible to abandon the use of large amounts of pesticides, which are now being spent on containing a number of insect pests. Among the primary goals, the authors of the method name mosquitoes from the genus Aedes, which spread yellow fever, dengue fever, Zika virus and many other diseases.

As the authors point out, the main condition for the possibility of applying their method is the presence in insects of such types of symbiont bacteria that could be cultivated in laboratory conditions. It is already clear that in addition to Aedes mosquitoes, such insects include Anopheles mosquitoes (malaria vectors), tsetse fly (sleeping sickness vector), citrus whitefly (pest of fruit plants), as well as honey bee.

For each insect species that people want to influence with the help of RNA interference, it is planned to determine a specific type of symbiont bacteria that lives only in the body of this insect. And you also need to identify a gene or several genes whose work is to be regulated. To do this, it will be possible to use data that is currently being collected as part of a large-scale i5k project dedicated to reading the genomes of 5,000 species of insects and other arthropods.

The impact on the work of the insect genome, which will be carried out with the help of symbionto-mediated RNA interference, can be not only disastrous. Perhaps this method will solve many problems associated with honey bees and other valuable pollinators, making them more resistant to pathogens.

The results of the experiment are presented in an article published by the journal Proceedings of the Royal Society B (Whitten et al., Symbiont-mediated RNA interference in insects).

Portal "Eternal youth" http://vechnayamolodost.ru  14.03.2016