Generation of Full-Length cDNAs for Eight Putative GPCnR from the Cattle Tick, R. microplus Using a Targeted Degenerate PCR and Sequencing Strategy

We describe here a rapid and efficient method for the targeted isolation of specific members of gene families without the need for cloning. Using this strategy we isolated full length cDNAs for eight putative G-protein coupled neurotransmitter receptors (GPCnR) from the cattle tick Rhipicephalus (Boophilus) microplus. Gene specific degenerate primers were designed using aligned amino acid sequences of similar receptor types from several insect and arachnid species. These primers were used to amplify and sequence a section of the target gene. Rapid amplification of cDNA ends (RACE) PCR was used to generate full length cDNA sequences. Phylogenetic analysis placed 7 of these sequences into Class A G-protein coupled receptors (GPCR) (Rm_α2AOR, Rm_β2AOR, Rm_Dop1R, Rm_Dop2R, Rm_INDR, Rm_5-HT7R and Rm_mAchR), and one into Class C GPCR (Rm_GABABR). Of the 7 Class A sequences, only Rm_mAchR is not a member of the biogenic amine receptor family. The isolation of these putative receptor sequences provides an opportunity to gain an understanding of acaricide resistance mechanisms such as amitraz resistance and might suggest possibilities for the development of new acaricides.