Transgenic rice overexpressing insect endogenous microRNA csu-novel-260 is resistant to striped stem borer under field conditions.

Abstract

RNA interference (RNAi) is a promising approach for developing insect-resistant crops. In the first two proof-of-concept studies, DNA fragments derived from essential insect genes were constructed into plant expression cassettes as inverted repeats, enabling long double-stranded RNAs (dsRNAs) to be transcribed in host plants (Baum et al., 2007; Mao et al., 2007). After ingestion, dsRNAs overexpressed in planta suppressed target gene expression via small interference RNA (siRNA)-mediated RNAi in western corn rootworm (Diabrotica virgifera virgifera) (Baum et al., 2007) and cotton bollworm (Helicoverpa armigera) (Mao et al., 2007), and thereby reduced their viability. Subsequent studies have mostly employed a similar approach and attempted to develop RNAi crops against various insect species (Liu et al., 2020). However, except for coleopterans that are generally susceptible to RNAi, most insects (e.g., lepidopterans, dipterans, hymenopterans, and hemipterans) exhibit unpredictable responses to dsRNA-induced RNAi, and this has become a hurdle for ubiquitous adaption of this strategy (Cooper et al., 2019). Potential factors influencing RNAi efficacy in insects involve dsRNA stability, cellular dsRNA absorption, core RNAi machinery integrity, systemic RNAi spread, and target gene amenability (Cooper et al., 2019).