Non-palm Plant Volatile α-Pinene Is Detected by Antenna-Biased Expressed Odorant Receptor 6 in the Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae)

Abstract

The majority of insects rely on a highly complex and precise olfactory system to detect various volatile organic compounds released by host and non-host plants in environments. The odorant receptors (ORs) are considered to play an important role in odor recognition and the molecular basis of ORs, particularly in coleopterans they are relatively poorly understood. The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is one of the most destructive pests of the global palm industry. Although feeding and egg oviposition behaviors of RPW can be repelled by some non-palm plant volatiles, such as α-pinene, geraniol, or 1-octen-3-ol, there is limited understanding of how RPW recognizes the non-host plant volatiles. In this study, three candidate RferOrs were identified from the Rfer-specific clade, and the tissue expression analysis used was mainly expressed in the antennae of both sexes. Functional characterization of RferOr6, RferOr40, and RferOr87 was analyzed by using the Xenopus oocyte expression system, and the results indicated that RferOr6/RferOrco was narrowly tuned to α-pinene. The behavioral experiment showed that α-pinene at the concentrations of 10 and 100 μg/μl can cause a significantly repelled behavioral response of RPW. In conclusion, this study reveals that RferOr6 is an antenna-biased expressed OR used by RPW to detect the volatile compound α-pinene in non-palm plants, and our results provide a foundation for further in vivo functional studies of Or6 in RPW, including in vivo knockout/knockdown and feeding/ovipositing behavioral studies of RPW and further pest control.

Odorant receptor orthologues in conifer‐feeding beetles display conserved responses to ecologically relevant odours

“…In contrast, nothing is known about the functions of OR orthologues in beetles, which is not surprising given the very few ORs that have been functionally characterized in this large order. The response profiles of seven ORs have been characterized from the Eurasian spruce bark beetle Ips typographus L. (“Ityp”; Curculionidae) (Hou et al, 2021; Roberts et al, 2021; Yuvaraj et al, 2021), two ORs from the red palm weevil Rhynchophorus ferrugineus Olivier (Curculionidae) (Antony et al, 2021; Ji et al, 2021), one OR from the dark black chafer Holotrichia parallela Motschulsky (Scarabaeidae) (Wang et al, 2020), one OR from the Adonis ladybird Hippodamia variegata Goeze (Coccinellidae) (Xie et al, 2022) and three ORs from the hickory borer Megacyllene caryae Gahan (“Mcar”; Cerambycidae) (Mitchell et al, 2012). Among the characterized ORs of this cerambycid, McarOR5 responded strongly to the male‐produced pheromone component 2‐phenylethanol (2‐PE) (Mitchell et al, 2012).…”

Odorant receptor orthologues in conifer-feeding beetles display conserved responses to ecologically relevant odors

“…In contrast, nothing is known about the functions of OR orthologues in beetles, which is not surprising given the very few ORs that have been functionally characterized in this large order. The response profiles of seven ORs have been characterized from the Eurasian spruce bark beetle Ips typographus L. (‘Ityp’; Curculionidae) (Hou et al 2021; Roberts et al 2021a; Yuvaraj et al 2021), two ORs from the red palm weevil Rhynchophorus ferrugineus Olivier (Curculionidae) (Antony et al 2021; Ji et al 2021), one OR from the dark black chafer Holotrichia parallela Motschulsky (Scarabaeidae) (Wang et al 2020), one OR from the Adonis ladybird Hippodamia variegata Goeze (Coccinellidae) (Xie et al 2022) and three ORs from the hickory borer Megacyllene caryae Gahan (‘Mcar’; Cerambycidae) (Mitchell et al 2012). Among the characterized ORs of this cerambycid, McarOR5 responded strongly to the male-produced pheromone component 2-phenylethanol (2-PE) (Mitchell et al 2012).…”

Expression Profiling and Functional Analysis of Candidate Odorant Receptors in Galeruca daurica

“…The tissue expression profiles of 21 ORs showed that most OR genes ( GdauOR1 , GdauOR3 - 6 , GdauOR8 , GdauOR11 - 13 , GdauOR15 , GdauOR17 - 20 , and GdauORco ) were highly expressed in antennae, which were similar to the results in other species [ 9 ]. This result suggested that these ORs might be involved in the chemosensory process [ 34 , 35 , 36 ]. Notably, GdauORco and GdauOR4 were extremely highly expressed in antennae, suggesting that they may play an important role in the olfactory system.…”