RNA interference (RNAi) is a biological process in which endogenesis or external-origin double-stranded RNA (dsRNA) inhibit gene expression or translation. Such a process is common in natural organisms. According to research, scientists discovered RNAi in the 1990s, and since then, it has become evident that RNAi has enormous potential in the suppression of target genes. RNAi has been applied in entomology research and the development of innovative pesticides in the past few years, thanks to its high efficiency, species specificity and ease of application.
How does RNAi protect crops from insect pests?
RNAi interferes with the insect’s gene expression, and prevents protein synthesis, thus decreasing the insect’s adaptability to the environment or leading to its death. To make external-origin dsRNA work for crop protection, pest feeding on the dsRNA is the main way to start the RNAi process. The dsRNA can be absorbed in the insect’s midgut. If the target gene is not in the midgut, the interference signal can be passed through cells and eventually reaches the gene to inhibit its expression.
There are mainly five types of target genes that RNAi works on to control insects, namely lethal gene, resistance/immunity-related gene (to decrease the resistance of insects to pesticides), growth/development-related gene, oviposition-related gene, and the olfactory gene (to prevent insects from identifying crops).
The most popular way to introduce dsRNA into insects is through feeding. This method is easy to implement, no special equipment is required, and it is convenient to study RNAi using this approach. It has been successfully utilized to control many species of pests, such as Nilaparvata lugen, Reticulitermes flavipes, Rhodnius prolixus, Diabrotica virgifera, etc. However, it might provide slow-killing efficacy, and is invalid to pests at the egg or pupal stage since they feed on nothing.
Advantages of RNAi applied for pest control
1) Due to the high specificity of dsRNA, such a technology has a small effect on non-target organisms.
2) As RNAi naturally occurs in the environment or organisms, and is biodegradable, the toxicity potential of RNA pesticides is lower than that of chemical pesticides.
3) RNA pesticides can be developed to control all species of pests. While comparing such products to Bt technology, for example, scientists have found that Bt crops provide limited control on sucking insects as Bt toxins have hardly any effect on them,