Identification and characterization of genes differentially expressed in the testis/vas deferens of the fed male tick, Amblyomma hebraeum.

Most ixodid ticks must feed for at least a few days to complete gonad maturation. Substances produced by the mature male gonad, and carried in the spermatophore, induce physiological changes in the female that lead to engorgement and oviposition. To begin defining the molecular phenotype at this stage of male development, we differentially cross-screened a cDNA library made from the testis and vas deferens of fed ticks (Amblyomma hebraeum Koch) and isolated 35 genes that were putatively up-regulated in tissues of fed compared to unfed animals. While the majority of these were novel, two clones, AhT/VD16 and AhT/VD146, yielded homologies (53 and 44%) to known genes (acylphosphatse and 9.0 kD Drosophila melanogaster basic protein, respectively). Results of Northern blot analysis of AhT/VD16 and AhT/VD146 demonstrate that both clones hybridized with mRNA transcripts that were up-regulated in the testis/vas deferens of fed compared to unfed males. In addition, hybridization of clone AhT/VD16 to water strider (Gerris argentatus) genomic DNA, and sequence similarities to mammalian acylphosphatase, suggest that it represents an evolutionarily conserved sequence.