Alternative structured dsRNAs and their potential to enhance RNAi in insects

Double-stranded RNA-based insecticides offer the potential to control pest insects with minimal impacts on non-target species, which makes them an appealing alternative to our broad-spectrum chemical pesticides. While double-stranded RNA (dsRNA) is more durable than single-stranded RNA, it is nevertheless still prone to degradation, and hence, various approaches have been developed to enhance its stability in the field. For crop protection applications, two approaches have been developed: 1) transgenic plants that produce the dsRNA within their tissues; and 2) foliar dsRNA sprays, which can be combined with various adjuvants that can either protect the dsRNA on the plant’s surface or enable the dsRNA to penetrate partially or fully into the plant’s tissues. Our research group has been testing different structured dsRNAs for their durability against nucleases, while still serving as suitable substrates for Dicer, a key enzyme mediating RNA interference. Combining different structured RNAs with various adjuvants, we have identified effective formulations that improve the efficacy of foliar dsRNA sprays, and have identified RNA structures that can facilitate RNAi in insects that are partially refractory to conventional, linear dsRNAs. The different structured dsRNAs could serve as useful alternatives in the development of dsRNA-based insecticides for species where conventional dsRNAs have been largely ineffective for pest control.