TRPA1 modulates noxious odor responses in Lygus hesperus

Authors: Hull, Joe; Yang, Yu-Wen; Miyasaki, Katelyn; Brent, Colin

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2020
Publication Date: 4/1/2020
Citation: Hull, J.J., Yang, Y., Miyasaki, K.F., Brent, C.S. 2020. TRPA1 modulates noxious odor responses in Lygus hesperus. Journal of Insect Physiology. 122. https://doi.org/10.1016/j.jinsphys.2020.104038.
DOI: https://doi.org/10.1016/j.jinsphys.2020.104038

Interpretive Summary: Lygus hesperus is a key pest of many economically important crops across western North America. Central to many aspects of the lives of these insects is chemical signaling, with identified roles in host plant selection, aggregation and passive mate guarding. The development of novel monitoring and control approaches for this insect will rely on a sound understanding of how these cues are perceived, processed and responded to. Towards this end, we investigated three compounds that are noxious repellents to other insects. We found that exposure to each of the compounds caused increases in movement velocity and duration in both nymphs and adults, suggesting they may have a role as repellents. To better understand how the physiology of this response, gene silencing was used to individually inhibit the expression of two proteins typically associated with insect perception of odorants. While inhibition of one, the odorant receptor co-receptor (Orco), had no behavioural effect, silencing the other, the transient receptor potential A (TRPA1), effectively eliminated the typical response to a noxious odorant, suggesting it has a key role in detecting noxious compounds.

Technical Abstract: Lygus hesperus is a key pest of many economically important crops across western North America. Central to many aspects of the lives of these insects is chemical signalling, with identified roles in host plant selection, aggregation and passive mate guarding. The development of novel monitoring and control approaches for this insect will rely on a sound understanding of how these cues are perceived and processed, and their impact on behavior. Towards this end, we investigated allyl isothiocyanate, cinnamaldehyde and citronellal, compounds that are noxious repellents to other insects. We found that L. hesperus avoided areas containing the three compounds and that exposure induced increases in movement velocity and duration in both nymphs and adults. This suggests these compounds may work as repellents. To better understand the underlying physiology of this response, RNA interference by dsRNA injection was used to inhibit the expression of two chemosensory-associated proteins, the odorant receptor co-receptor (Orco) and the transient receptor potential A (TRPA1) channel. While knockdown of Orco did not change the reaction of adult females to citronellal, TRPA1 silencing effectively eliminated the induced increase to movement, suggesting a chemoperceptory role in citronellal detection.