Mining Lygus hesperus (western tarnished plant bug) transcriptomic data for transient receptor potential channels: Expression profiling and functional characterization of a painless homolog

Authors: Hull, Joe; Brent, Colin; FU, TING - Chinese Academy Of Agricultural Sciences; WANG, GUIRONG - Chinese Academy Of Agricultural Sciences; CHRISTIE, A - University Of Hawaii

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2022
Publication Date: 10/13/2022
Citation: Hull, J.J., Brent, C.S., Fu, T., Wang, G., Christie, A.E. 2022. Mining Lygus hesperus (western tarnished plant bug) transcriptomic data for transient receptor potential channels: Expression profiling and functional characterization of a painless homolog. Comparative Biochemistry and Physiology. 44. Article 101027. https://doi.org/10.1016/j.cbd.2022.101027.
DOI: https://doi.org/10.1016/j.cbd.2022.101027

Interpretive Summary: The evolutionarily conserved transient receptor potential (TRP) family of membrane bound ion channels are critical for the perception of various environmental cues including heat, cold, pain, movement, and touch. The TRP channel family is comprised of seven subfamilies that can in turn be broadly arranged into two groups based on sequence and topological similarities. Despite extensive studies in model species, our understanding of TRP channel functional diversity and physiological impact remains limited in many non-model agricultural pest species such as the western tarnished plant bug (WTPB). To begin to understand how the TRP family functions in WTPB, previously generated WTPB sequence databases were searched for TRP channel-like sequences. The potential TRP channel complement identified exceeded that reported for most insects. One potential TRP channel termed Painless was selected for more in depth analysis and its functional role in heat sensation was examined. WTPB Painless is expressed in most tissues as well as throughout nymphal and adult development and functional analyses revealed that the channel is strongly activated by heat in the 40º-45ºC range. These data provide base-line information for better understanding the molecular basis of WTPB physiology and can be used to facilitate the development of improved biological-based management strategies.

Technical Abstract: The transient receptor potential (TRP) family of cation channels are evolutionarily conserved proteins with critical roles in sensory physiology. Despite extensive studies in model species, knowledge of TRP channel functional diversity and physiological impact remains limited in many non-model insect species. To assess the TRP channel repertoire in a non-model agriculture pest species (Lygus hesperus), publicly available transcriptomic datasets were mined for potential homologs. Among the transcripts identified, 30 are predicted to encompass complete open reading frames that encode proteins representing each of the seven TRP channel subfamilies. Although no homologs were identified for the Pyrexia and Brivido channels, the TRP complement in L. hesperus exceeded the 13-16 channels reported in most insects. This diversity appears to be driven by a combination of alternative splicing, which impacted members of six subfamilies, and gene expansion of the TRPP subfamily. To validate the in silico data and provide more detailed analyses of L. hesperus TRP functionality, the putative Painless homolog was selected for more in depth analysis and its functional role in thermosensation examined in vitro. RT-PCR expression profiling revealed near ubiquitous expression of the Painless transcript throughout nymphal and adult development. Electrophysiological data generated using a Xenopus oocyte recombinant expression system indicated activation parameters for L. hesperus Painless homolog that are consistent with a role in noxious heat (40º-45ºC) thermosensation.