Molecular cloning and characterization of G alpha proteins from the western tarnished plant bug, Lygus hesperus

Authors: Hull, Joe; WANG, MEIXIAN - Zhejian University

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2014
Publication Date: 12/31/2014
Publication URL: http://handle.nal.usda.gov/10113/60136
Citation: Hull, J.J., Wang, M. 2014. Molecular cloning and characterization of G alpha proteins from the western tarnished plant bug, Lygus hesperus. Insects. 6(1):54-76.

Interpretive Summary: G-proteins are members of a large family of specialized molecules that communicate signals from outside of cells to their interior, setting off a cascade of actions. These proteins, which are composed of three subunits (alpha, beta, and gamma), are thought to play a key role in chemosensation (taste, smell), but this role is not completely understood. We identified nine different G-protein alpha subunits from the western tarnished plant bug, which is an important crop pest in the western U.S. The nine subunits represented four families of alpha subunits, one of which was represented by five variants. A variant of one subunit (LhG-alpha q2) was only present in eggs. Another variant (LhG-alpha q4) was only present in insect heads. The remaining subunits and variants were present at varying levels throughout the insect body. All of the alpha-subunit families were identified from insect organs associated with chemoreception, suggesting they play a role in smell or taste. Our results represent the first step in defining the role of G-proteins in chemical communications of the western tarnished plant bug, which may lead to development of novel, molecular-based management tactics for this pest.

Technical Abstract: The G-alpha subunits of heterotrimeric G proteins play critical roles in the activation of diverse signal transduction cascades. However, the role of these genes in chemosensation remains to be fully elucidated. To initiate a comprehensive survey of signal transduction genes, we used homology-based cloning methods and transcriptome data mining to identity G-alpha subunits in the western tarnished plant bug (Lygus hesperus Knight). Among the nine sequences identified were single variants of the G-alpha i, G-alpha o, G-alpha s, and G-alpha 12 subfamilies and five alternative splice variants of the G-alpha q subfamily. Sequence alignment and phylogenetic analyses of the putative L. hesperus G-alpha subunits support initial classifications and are consistent with established evolutionary relationships. End-point PCR-based profiling of the transcripts indicated egg specific expression for LhG-alpha q2, head specific expression for LhG-alpha q4, and ubiquitous expression, albeit at varying levels, for the other LhG-alpha transcripts. All subfamilies were amplified from L. hesperus chemosensory tissues, suggesting potential roles in olfaction and/or gustation. Immunohistochemical staining of cultured insect cells transiently expressing recombinant His-tagged LhG-alpha i, LhG-alpha s, and LhG-alpha q1 revealed plasma membrane targeting, suggesting the respective sequences encode functional G protein subunits.