REVIEW ARTICLE The advent of RNA interference in Entomology Taro MITO, Taro NAKAMURA, Tetsuya BANDO, Hideyo OHUCHI and Sumihare NOJI Department of Life Systems, Institute of Technology and Science, University of Tokushima, Tokushima City, Japan Abstract RNA interference (RNAi) is a cellular process by which an mRNA is targeted for degradation by a small interfering RNA that contains a strand complementary to a fragment of the target mRNA, resulting in sequence specific inhibition of gene expression. The discovery of RNAi enabled the use of loss-of-function analyses in many non-model insects other than Drosophila to elucidate the roles of specific genes. The RNAi approach has been widely used on insects in several fields, including embryogenesis, pattern formation, reproduction, biosynthesis and behavior. The increasing availability of insect genomes has made the RNAi technique an indispensable technique for characterizing gene functions in insects. Here we review the current status of RNAi-based experiments in insects and the applications of RNAi for species-specific insecticides, focusing on non-drosophilid insects. We also identify future applications for RNAi-based studies in Entomology. Key words: development, insecticides, insects, loss-of-function, regeneration, RNAi. INTRODUCTION The recognition of RNA interference (RNAi) as a method for analyzing the functions of individual genes culminated with the awarding of the Nobel Prize for the discovery of RNAi (Fire et al. 1998) to Andrew Z. Fire and Craig C. Mello in 2006. This discovery has paved an easier way for the use of loss-of-function analyses in many animals, including insects. Before the discovery of RNAi, it was almost impossible to analyze the functions of genes in insects for which genetic analyses are diffi- cult. Now, RNAi allows the rapid and straightforward analysis of gene function in non-model insects. Cur- rently, many RNAi-based studies with various insects are in progress, and several reviews on their results have already been published. In particular, Bellés (2010) com- prehensively reviewed RNAi-based studies on insects, covering some 30 species representing nine orders. However, this approach is still relatively new, and this field will continue to expand as the number of insect genome projects increases and as RNAi methods are used to analyze the functions of new genes. Even in Drosophila melanogaster, after the completion of its genomic sequencing, a large number of genes whose functions are unknown were identified, and their func- tions have been investigated with RNAi methods (Mathey-Prevot & Perrimon 2006). Thus, the combina- tion of genomic sequencing projects with RNAi methods will lead to an increase in our understanding of gene functions. In this review, we focus on two topics: (i) the current status of RNAi-based experiments in non- drosophilid insects and (ii) the applications of RNAi as species-specific insecticides. Finally, we discuss the future of RNAi-based studies in Entomology. CURRENT STATUS OF RNAI-BASED EXPERIMENTS IN INSECTS The advent of RNAi represents a new experimental paradigm beyond Drosophila, as it opens the door to the study of gene functions in other species (Bellés 2010). In 1999, Brown et al. (1999) showed that RNAi could be used to phenocopy the mutations of the Deformed orthologue in the flour beetle, Tribolium castaneum. In 2000, Hughes and Kaufman (2000) reported the use of RNAi to dissect gene function in the development of the milkweed bug, Oncopeltus fasciatus, which undergoes Correspondence: Taro Mito and Sumihare Noji, Department of Life Systems, Institute of Technology and Science, University of Tokushima, 2-1 Minami-Jyosanjima-cho, Tokushima City 770-8506, Japan. Email: mito@bio.tokushima-u.ac.jp; noji@bio.tokushima-u.ac.jp Received 5 May 2010; accepted 16 June 2010. Entomological Science (2011) 14, 1–8 doi:10.1111/j.1479-8298.2010.00408.x © 2010 The Entomological Society of Japan