Far-Western blots, enzyme-linked immunosorbent assays, and co-immunoprecipitation assays revealed that Bmdimm protein interacted with another basic helix-loophelix transcription factor, Bmsage. Immunostaining revealed that BmdimmandBmsageproteinsareco-localizedinnuclei.Bmdimm expression was induced in larval silk glands in vivo, in silk glands cultured in vitro, and in B. mori cell lines after treatment with a JH analog. The JH effect on Bmdimm was mediated by the JH-MetKr-h1signalingpathway,andBmdimmexpressiondidnotrespond to JH by RNA interference with double-stranded BmKr-h1 RNA. These data suggest that the JH regulatory pathway, the transcriptionfactorBmdimm,andthetargetedfib-Hgenecontributetothe synthesis of fibroin H-chain protein in B. mori.