Differential protein expression in ovaries of uninfected and Babesia-infected southern cattle ticks, Rhipicephalus (Boophilus) microplus

Authors: Rachinsky, Anna; Guerrero, Felicito; Scoles, Glen

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2007
Publication Date: 12/5/2007
Citation: Rachinsky, A., Guerrero, F.D., Scoles, G.A. 2007. Differential protein expression in ovaries of uninfected and Babesia-infected southern cattle ticks, Rhipicephalus (Boophilus) microplus. Insect Biochemistry and Molecular Biology. 37:1291-1308.

Interpretive Summary: The southern cattle tick, Rhipicephalus (Boophilus) microplus, serves as a vector for the protozoan agents of cattle fever, Babesia bovis and Babesia bigemina. Although the southern cattle tick was declared eradicated from the US by 1943, the potential re-introduction of cattle ticks on cattle imported from Mexico, where cattle fever is endemic and tick populations are abundant, pose a continuous threat to the US cattle industry. There is great need for new, environmentally safe and effective techniques for control of southern cattle ticks that can be integrated with conventional chemical control methods. Developing novel pest control strategies can be facilitated by knowledge of the molecular biology of the cattle tick. The aim of this study was to gather information about the ticks’ ovarian proteins, with particular emphasis on proteins that are differentially expressed in response to infection with cattle fever-causing protozoa. Membrane proteins were extracted from tick ovaries and analyzed using gel electrophoresis and mass spectrometry. We were able to identify nineteen differentially expressed proteins. The identification of differentially expressed proteins in tick ovaries will increase our understanding of infection-induced changes that occur in the tick host in general, and may allow us to elucidate the interactions that occur between ticks and the cattle fever-causing protozoa in the ovaries. Understanding these molecular interactions will aid in the identification of novel targets for improved tick control strategies, including identification of potential targets for the development of anti-tick and/or transmission blocking cattle vaccines.

Technical Abstract: We used gel electrophoresis and mass spectrometry to investigate differences in protein expression in ovarian tissues from Babesia bovis-infected and uninfected southern cattle tick, Rhipicephalus (Boophilus) microplus. Soluble and membrane proteins were extracted from ovaries of adult female ticks, and analyzed by isoelectric focusing (IEF) and one-dimensional or two-dimensional (2-D) gel electrophoresis. Protein patterns were analyzed for differences in expression between infected and uninfected ticks. 2-D separation of proteins revealed a large number of proteins that appeared to be up- or down-regulated in response to infection with Babesia, in particular membrane/membrane-associated proteins and proteins in a low molecular mass range between 6 and 36 kDa. A selection of differentially expressed proteins were subjected to analysis by capillary-HPLC-electrospray tandem mass spectrometry (HPLC-ESI-MS/MS) mass spectrometry. Among the ovarian proteins that were up-regulated in infected ticks were calreticulin, two myosin subunits, an endoplasmic reticulum protein, a peptidyl-prolyl cis-trans isomerase (PPIase), a cytochrome c oxidase subunit, a glutamine synthetase, and a family of Kunitz-type serine protease inhibitors. Among the down-regulated ovarian proteins were another PPIase, a hemoglobin subunit, and a lysozyme. This study is part of ongoing effort to establish a proteome database that can be utilized to investigate specific proteins involved in successful pathogen transmission.