Involvement of Two Paralogous Methoprene-Tolerant Genes in the Regulation of Vitellogenin and Vitellogenin Receptor Expression in the Rice Stem Borer,Chilo suppressalis

Besides the function of preventing metamorphosis in insects, the juvenile hormone (JH) plays a role in female reproduction; however, the underlying mechanism is largely unknown. The methoprene-tolerant (Met) protein belongs to a family of basic helix-loop-helix-Per-Arnt-Sim (bHLH-PAS) transcription factors and functions as the JH intracellular receptor. In this study, two full length cDNAs encodingMet(CsMet1andCsMet2) were isolated from the rice stem borer,Chilo suppressalis.Structural analysis revealed that bothCsMet1andCsMet2exhibited typical bHLH, PAS-A, PAS-B, and PAC (PAS C terminal motif) domains. Comparative analysis of transcript level using reverse transcription-quantitative PCR (RT-qPCR) revealed thatCsMet1was predominant in almost all examined developmental stages and tissues. Treatment with methoprenein vivoinduces the transcription of bothCsMet1andCsMet2.Notably, injection of dsCsMet1 and dsCsMet2 suppressed the expression levels of vitellogenin (CsVg) and Vg receptor (CsVgR). These findings revealed the potential JH signaling mechanism regulatingC. suppressalisreproduction, and provided evidence that RNAi-mediated knockdown ofMetholds great potential as a control strategy ofC. suppressalis.