Bruceine D Acts as a Potential Insecticide by Antagonizing 20E-EcR/USP Signal Transduction

BruceineD (BD) is an effective insecticidal compound found inthe Chinese herb Brucea javanica (L.)Merr. BD inhibits the growth and metamorphosis of Plutellaxylostella and Drosophila melanogaster; however, its target protein and the molecular mechanism of insecticidalactivity remain unclear. In this study, proteins with high affinityfor BD were screened using surface plasmon resonance and high-performanceliquid chromatography coupled with matrix-assisted laser desorption/ionization-time-of-flightmass spectrometry, revealing the ecdysone receptor (EcR) is the maintarget of BD. In vivo results showed that BD inhibitedinsect growth and metamorphosis through inhibition of the expressionof 20E response genes. In vitro dual luciferase andenhanced green fluorescent protein (EGFP) fluorescence experimentsindicated that BD suppressed the transcriptional activation activityof EcR by blocking the ecdysone response element (EcRE)-triggeredtranscriptional cascade, suggesting that BD inhibits the formationof the 20E-EcR-USP-EcRE complex. Moreover, moleculardocking demonstrated that BD bound well to EcR. Elucidating the insecticidalmechanism of BD will be helpful in the development of green pesticidesto control pests.