Homothorax regulates BarH1 expression and olfactory perception in Monochamus alternatus hope

Odorant-binding proteins (OBPs) play a crucial role in the host location of the Japanese pine sawyer beetle, Monochamus alternatus, a significant forest pest responsible for the transmission of pine wilt disease. We previously identified BarH1 as a direct regulator of the odorant-binding protein Obp19; however, its upstream regulation remains unclear. In this study, we delineate a sexually dimorphic transcriptional network that governs BarH1 expression and olfactory plasticity. We identified critical cis-regulatory elements in the MaltBarH1 promoter, including an enhancer (-3035 to -2677 bp) and a repressor (-2677 to -2560 bp) that finely modulate its transcription. Yeast one-hybrid screening revealed Homothorax (Hth) as a key upstream activator that specifically binds to the MaltBarH1 promoter. Notably, this network exhibits marked sexual dimorphism: females display sustained upregulation of BarH1-Obp19 following exposure to camphene, whereas males exhibit suppression. Behaviorally, Hth knockdown specifically transformed male attraction to camphene into repulsion, while females remained unaffected. Our findings establish MaltBarH1 as an integrative hub within a sex-specific regulatory circuit that processes olfactory information distinctly between the sexes. This work provides novel insights into insect chemosensory plasticity and identifies potential targets for pest management strategies.