Molecular Cloning and Characterization of G Alpha Proteins from the Western Tarnished Plant Bug, Lygus hesperus

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 head specific expression for LhG alpha q4, and largely 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.