Anaplasma ovis, a tick-borne intra-erythrocytic Gram-negative bacterium, is a causative agent of ovine anaplasmosis. It is known that Dermacentor ticks act as biological vectors for A. ovis. VirD4 is the machine component of Type IV Secretion System of A. ovis. To better understand the pathogen-vector interaction, VirD4 was used as a bait protein for screening midgut proteins of Dermacentor silvarum via yeast two-hybrid mating assay. As a result, a ribosomal protein RL12 was identified from the midgut cDNA library of D. silvarum. For further validation, using in vitro Glutathione S-transferase (GST) pull-down assay, interaction between the proteins, GST-RL12 and HIS-VirD4, was observed in Western blot analysis. The study is first of its kind reporting a D. silvarum midgut protein interaction with VirD4 from A. ovis. Functional annotations showed some important cellular processes are attributed to the protein, particularly in the stringent response and biogenesis. The results of the study suggest the involvement of the VirD4-RL12 interaction in the regulation of signaling pathways, which is a tool for understanding the pathogen-vector interaction.
