Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/26/2004
Publication Date: 1/27/2005
Citation: Untalan, P.M., Guerrero, F.D., Haines, L.R., Pearson, T.W. 2005. Proteome analysis of abundantly expressed proteins from unfed larvae of the cattle tick, Boophilus microplus. Insect Biochemistry and Molecular Biology. 35:141-151. Interpretive Summary: The cattle tick is an economically important parasite that affects cattle worldwide, including North America, with an estimated $70 million (US) annual cost to the cattle industry in Australia alone. The cattle tick was successfully eradicated from the United States in 1943 and a quarantine zone is maintained along the Texas-Mexico border to prevent the reentry of the tick into the USA. The stringent quarantine program at import facilities involves the physical inspection and dipping of cattle in vats of coumaphos (an organophosphate (OP)-type acaricide), prior to their importation. Tick control in Mexico has primarily focused on acaricide treatment of livestock, and this has contributed to the development of acaricide resistant populations of ticks, including documented cases of resistance to coumaphos treatment. This issue has raised concern that the quarantine program may become ineffective should resistance become high enough to permit ticks to survive the dipping treatment. In recent years, the development of new chemical control methods for the tick has slowed. This has increased interest in the investigation of alternative, possibly novel, control strategies for the tick. One approach to identifying new control targets involves analyzing the proteins that are expressed by an OP-sensitive and -resistant strain of the cattle tick, in response to acaricide exposure, and studying those proteins that are expressed differently. The current work describes the isolation and resolution of proteins from larvae of two such strains using protein analysis methodologies that, to our knowledge, have not been utilized for studies of the cattle tick. This pilot study was conducted using larval material that had not been exposed to acaricide in order to characterize any inherent differences that might exist between the strains. Eight proteins from the study were selected for more in-depth analysis, which includes obtaining protein sequence information, comparing this information to a public database of sequences, and assigning putative identities to the proteins based on similarity of their sequence to those in the database. Four of these identified proteins, expressed abundantly in both strains, may play roles in larval motility, energy supply, and general cellular maintenance. Data from four additional proteins did not display similarity to reported sequences in the database, suggesting they may be novel proteins. Three of these proteins were abundantly expressed in both strains, while one protein appeared to be consistently expressed at a markedly higher level in OP-resistant larvae. This work lays the foundation for the establishment of a database of proteins that are not only expressed during the larval stage of development, but at other stages and in specific tissues that are critical for tick survival as well
Technical Abstract: We used gel electrophoresis and mass spectrometry to characterize basal protein expression in larvae from acaricide-resistant and -sensitive strains of the cattle tick, Boophilus microplus. Soluble and insoluble proteins were extracted from unfed larvae of organophosphate-susceptible and -resistant tick strains, and resolved by one-dimensional (1-D) and two-dimensional (2-D) gel electrophoresis. Eight abundant proteins were selected for peptide mass mapping and for peptide sequencing by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and quadrupole time-of-flight (Q-TOF) tandem mass spectrometry, respectively. Only one protein, tropomyosin, was unequivocally identified from its peptide mass map. Of the remaining seven proteins, four were assigned putative identities based on BLAST searching of heterologous databases with peptide sequences: a muscle-associated protein (troponin I), arginine kinase, a putative high-mobility group protein and a small heat shock protein. The three remaining proteins were not identified, suggesting that they may be novel molecules. It is exciting that one of these proteins (15 kDa) appeared to be markedly upregulated in acaricide-resistant larvae.