Pupal RNA interference methods for analyzing adult development in stag beetles

Holometabolous insects dramatically change their morphology via molt, both from larva to pupa and from pupa to adult. In nonmodel insects, RNA interference (RNAi) is a strong tool for analyzing gene function during postembryonic development. In many cases, larval RNAi is effective for analyzing genes involved in morphogenesis via metamorphosis. However, RNAi of genes involved in development sometimes results in lethality before animals metamorphose to pupae and/or adults, making it impossible to analyze their function during the pupal period. In this study, we establish a pupal RNAi system in the stag beetle Dorcus rectus. We selected the genes white and scarlet for RNAi knockdown to investigate appropriate injection timing and position. Both genes are known to be involved in eye pigmentation. By using these candidate genes, we demonstrate the potential of pupal RNAi in this experimental system. This method will be useful for analyzing pupal-specific morphogenesis including fine-shaping of the enlarged male mandible in this species.