| The major hemelipoglyco-carrier protein (CP) found throughout the development of male and female adult American dog ticks, Dermacentor variabilis (Say) was sequenced. DvCP is a single transcript coding for two protein subunits that together contain three motifs---(a) a lipoprotein n-terminal domain that is a common attribute of proteins that bind lipids, carbohydrates and metals, (b) a domain of unknown function characteristic of proteins with several large open beta sheets and (c) a von Willebrand factor type D domain near the carboxy-terminus apparently important for multimerization. These motifs also found in tick vitellogenin are not shared by heme-binding proteins studied thus far in other hematophagous insects. DvCP message was highest in fat body and salivary gland but was also found in midgut and ovary. Expression was initiated by blood feeding in virgin females and not by mating typical of tick vitellogenin (Vg); and the message was found in fed males at levels similar to part fed, virgin females. CP appears to be highly conserved among the Ixodida and shares a common origin with Vg. In the second part of this study, the tick synganglion transcriptome was studied by pyrosequencing to identify neuropeptides that regulate reproduction and development. Here we characterize fourteen putative neuropeptides (allatostatin, insulin-like peptide, ion-transport peptide, sulfakinin, bursicon alpha/beta, eclosion hormone, glycoprotein hormone alpha/beta, corazonin, four orcokinins) and five neuropeptide receptors (gonadotropin receptor, leucokinin-like receptor, sulfakinin receptor, calcitonin receptor, pyrokinin receptor) from the synganglion of female American dog ticks. Many of these neuropeptides have not been previously described in the Chelicerata. An insulin receptor substrate protein was also found indicating that at insulin signaling network is present in ticks. A putative type-2 proprotein processing convertase was also sequenced that may be involved in cleavage at monobasic and dibasic endoproteolytic cleavage sites in prohormone peptides. Quantitative real-time PCR was used to monitor developmental expression of these genes during adult female reproduction. Their physiological role during adult tick blood feeding and reproduction is be discussed. |
