2‑Phenylethanol and o‑Cresol Repel the Tomato Leaf Miner Phthorimaea absoluta and Attract the Parasitoid Trichogramma chilonis

Semiochemicals are biologically active compounds that
modulate
insect behaviors. Here, we applied a reverse chemical ecology approach
to identify 2-phenylethanol and o-cresol as behavior-modulating
compounds for Phthorimaea absoluta and its egg parasitoid Trichogramma chilonis. First, we identified that PabsOR27
is an odorant receptor (OR) that is highly expressed in the antennae.
We then deorphanized PabsOR27 as a receptor narrowly tuned to 2-phenylethanol
and o-cresol through ectopic expression in Drosophila olfactory receptor neurons and single-sensillum
recordings. Furthermore, molecular docking and mutagenesis revealed
Asparagine-199 as a critical amino acid residue that forms a hydrogen
bond with 2-phenylethanol. Moreover, behavioral tests confirmed that
both compounds act as repellents to P. absoluta,
significantly reducing oviposition on treated tomato plants. Conversely,
both compounds attract T. chilonis, enhancing its
parasitism against P. absoluta eggs. Collectively,
the dual roles of 2-phenylethanol and o-cresol position
them as promising candidates for developing “push–pull”
strategies for integrated pest management.