Molecular and functional characterization of pyrokinin-like peptides in the western tarnished plant bug lygus hesperus (Hemiptera: Miridae)

Authors: Hull, Joe; Brent, Colin; Choi, Man-Yeon; MIKO, ZSANETT - Plant Protection Institute - Hungary; FODOR, JOZSEF - Plant Protection Institute - Hungary; FONAGY, ADRIEN - Plant Protection Institute - Hungary

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2021
Publication Date: 10/6/2021
Citation: Hull, J.J., Brent, C.S., Choi, M.Y., Miko, Z., Fodor, J., Fonagy, A. 2021. Molecular and functional characterization of pyrokinin-like peptides in the western tarnished plant bug lygus hesperus (Hemiptera: Miridae). Insects. 12(10). Article 914. https://doi.org/10.3390/insects12100914.
DOI: https://doi.org/10.3390/insects12100914

Interpretive Summary: Neuropeptides regulate most insect biological functions. One such group of peptides, the pyrokinins (PKs), are widely distributed in most insects but poorly characterized in plant bugs. To address this limitation, we identified the PK gene transcript in the western tarnished plant bug (Lygus hesperus) and examined its expression. The Lygus PK transcript is predicted to yield three PK-like peptides but based on structure only two (LyghePKa and LyghePKb) may be functional. The transcript is expressed throughout development and is most abundant in heads. A custom antibody revealed immunoreactive cells throughout the Lygus central nervous system consistent with typical neuropeptide expression. Unlike most insects, four pairs of immunoreactive cells were found in the Lygus abdominal ganglion rather than the three pairs typical of most insects. Synthetic LyghePKb, but not LyghePKa, was able to activate a PK receptor in cell culture and was able to promote the production of pheromones in three species of moths. The study suggests unique evolutionary divergence of the PK gene in plant bugs and provides critical insights into likely biological functions in the western tarnished plant bug.

Technical Abstract: The pyrokinin (PK) family of insect neuropeptides, characterized by C termini consisting of either WFGPRLamide (i.e., PK1) or FXPRLamide (i.e., PK2), are encoded on the capa and pk genes. Although implicated in diverse biological functions, characterization of PKs in hemipteran pests has been largely limited to genomic, transcriptomic, and/or peptidomic datasets. The Lygus hesperus (western tarnished plant bug) PK transcript encodes a prepropeptide predicted to yield three PK2 FXPRLamide-like peptides with C-terminal sequences characterized by FQPRSamide (LyghePKa), FAPRLamide (LyghePKb), and a non-amidated YSPRF. The transcript is expressed throughout L. hesperus development with greatest abundance in adult heads. PRXamide-like immunoreactivity, which recognizes both pk- and capa-derived peptides, is localized to cells in the cerebral ganglia, gnathal ganglia/suboesophageal ganglion, thoracic ganglia, and abdominal ganglia. Immunoreac- tivity in the abdominal ganglia is largely consistent with capa-derived peptide expression, whereas the atypical fourth pair of immunoreactive cells may reflect pk-based expression. In vitro activation of a PK receptor heterologously expressed in cultured insect cells was only observed in response to LyghePKb, while no effects were observed with LyghePKa. Similarly, in vivo pheromonotropic ef- fects were only observed following LyghePKb injections. Comparison of PK2 prepropeptides from multiple hemipterans suggests mirid-specific diversification of the pk gene.