Glutathione S-Transferase Highly Expressed in Holotrichia parallela Antennae Inactivates the Odorant Unsaturated Aldehyde Volatiles

Odorant-degrading enzymes in insects play a vital rolein maintainingolfactory sensitivity. However, the role and molecular mechanism ofglutathione S-transferases (GSTs) in odorant inactivationhas been rarely studied. In the present study, 31 GSTs were identifiedfrom the antennal transcriptome of Holotrichia parallela. HpGSTd1 possesses the highest transcriptome expression level. RecombinantHpGSTd1 showed degradation activity toward various unsaturated aldehydevolatiles. Furthermore, the metabolite of cinnamaldehyde was identifiedby high-resolution mass spectrometry (HRMS). The molecular dockinganalysis and site-directed mutagenesis revealed the key residues ofHpGSTd1 in degrading odorants. In addition, the unsaturated aldehydevolatiles elicited the behavioral and electrophysiological responsesof H. parallela. Taken together, ourfindings suggest that HpGSTd1 may play an essential role in inactivatingodorants in H. parallela, which providesnew insights for identifying molecular targets and exploring effectiveolfactory regulators for this underground pest.

Automated summary

In this study, 31 glutathione S-transferases (GSTs) were identified from the antennal transcriptome of Holotrichia parallela, with HpGSTd1 showing the highest expression level. Recombinant HpGSTd1 was found to have degradation activity towards various unsaturated aldehyde volatiles, and the metabolite of cinnamaldehyde was identified using high-resolution mass spectrometry (HRMS). Molecular docking analysis and site-directed mutagenesis revealed the key residues of HpGSTd1 involved in odorant degradation. The unsaturated aldehyde volatiles also elicited behavioral and electrophysiological responses in H. parallela. These findings suggest that HpGSTd1 plays an essential role in inactivating odorants in this underground pest, providing new insights for identifying molecular targets and exploring effective olfactory regulators.