Two Minus-C odorant-binding proteins (OBPs) involved in the perception of kairomone (+)-3-carene in Dendroctonus valens

The olfactory system is pivotal for insects to detect external chemical signals and regulate essential life processes. Dendroctonus valens , an invasive forest pest, displays strong chemotaxis toward the plant kairomone (+)-3-carene. To unravel the molecular mechanism underlying olfactory recognition, we identified 28 odorant-binding proteins (OBPs) from D. valens via transcriptome sequencing and identified DvalOBP6 and DvalOBP18 as potential key candidates for this host kairomone component using qRT-PCR. Tissue expression analysis revealed that these two Minus-C OBPs are predominantly expressed in olfactory-related tissues (antennae, legs, and wings) with distinct sexual dimorphism. Homology modeling and molecular docking showed that both proteins adopt a typical six- α -helix fold, and bind (+)-3-carene primarily via hydrophobic interactions with binding energies of −5.53 kcal/mol and −4.96 kcal/mol, respectively. RNA interference of DvalOBP6 or DvalOBP18 significantly abolished the olfactory preference of D. valens adults for (+)-3-carene. Collectively, our findings demonstrate that DvalOBP6 and DvalOBP18 play critical roles in (+)-3-carene perception, providing a theoretical basis for the development of green pest control technologies targeting insect olfactory communication.