The Use of Nanocarriers to Improve the Efficiency of RNAi-Based Pesticides in Agriculture

Abstract

RNA interference (RNAi) is a post-transcriptional gene silencing mechanism whereby target gene messenger RNA (mRNA) is neutralized by double-stranded RNA (dsRNA) homologous to the mRNA sequence. The pathway can be exploited for pest and disease control purposes by delivery of exogenous dsRNA targeting a gene essential for the target organism’s survival. The most likely dsRNA delivery strategy for invertebrate pest control is through oral uptake, but transdermal dsRNA uptake has been reported to lead to gene silencing in some species as well. To combat plant-pathogenic fungi and viruses, methods that efficiently deliver dsRNAs into plant tissues are needed. While transgenic plants allow for efficient production of such dsRNAs in the plants, non-transgenic spray-based applications are being developed as well. Although RNAi is highly effective in some species, for example, certain beetle species, many insects and nematodes show a variable or lower sensitivity to dietary uptake of dsRNA. In the past decade, several factors and barriers affecting RNAi efficiency in insects have been identified, including dsRNA degradation in the insect body, inefficient cellular uptake of dsRNA, and an impaired endosomal escape into the cytoplasm. Nanocarriers could play a role in enhancing the efficacy of sprayable RNAi-based pesticides by helping to overcome some of these barriers. Several proof-of-concept studies have shown that polymers, liposomes, and peptides, among others could be used in this context but further advances are necessary to optimize these delivery systems. Gathering inspiration from the medical field, where RNAi is also being investigated as a potential therapeutics strategy, could drive forward these agricultural applications. In this chapter, we present an overview of the literature on RNAi barriers and the use of these nanoparticles to increase RNAi efficacy in agricultural pests. Finally, we also discuss a number of biosafety considerations regarding RNAi and the use of these nanoparticle formulations.