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Title: Global comparative analysis of ESTs from the southern cattle tick, Rhipicephalus (Boophilus) microplus

Author
item WANG, MINGHUA - LORUS THERAPEUTICS,CANADA
item Guerrero, Felicito
item PERTEA, GEO - TIGR, ROCKVILLE MD
item NENE, VISHVANATH - TIGR, ROCKVILLE MD

Submitted to: Genome Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2007
Publication Date: 10/12/2007
Citation: Wang, M., Guerrero, F., Pertea, G., Nene, V. 2007. Global comparative analysis of ESTs from the southern cattle tick, Rhipicephalus (Boophilus) microplus. BMC Genomics 8:368.

Interpretive Summary: The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an economically important parasite of cattle and can transmit several pathogenic microorganisms to its cattle host during the feeding process. Understanding the biology and genomics of R. microplus is critical to developing novel methods for controlling these ticks. A DNA sequence database containing 13,643 R. microplus expressed genes has been analyzed and compared to genes from other organisms. By identifying features which the tick genes have in common with previously identified and characterized genes from more well studied organisms, for example human, mouse, or fruit fly, functionality can be assigned to the newly sequenced tick genes. Using sequence analysis software, several tick genes have been identified which more closely resemble genes from mammals than insects. This unexpected result might be due to ticks and the mammalian hosts which they parasitize undergoing similar evolutionary pressures as they coexist in similar environmental conditions. Members of this group of genes would likely be poor choices as targets for development of novel tick control technology. A large fraction of BmiGI entries have no homologs in other sequenced genomes. This highlights the important insights in tick biology which are likely to result from a tick genome sequencing project.

Technical Abstract: Background: The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an economically important parasite of cattle and can transmit several pathogenic microorganisms to its cattle host during the feeding process. Understanding the biology and genomics of R. microplus is critical to developing novel methods for controlling these ticks. Results: We present a global comparative genomic analysis of a gene index of R. microplus comprised of 13,643 unique transcripts derived from 42,512 expressed sequence tags (ESTs), representing a significant fraction of the complement of R. microplus genes. The source material for these ESTs consisted of polyA RNA from various tissues, lifestages, and strains of R. microplus, including larvae exposed to heat, cold, host odor, and acaricide. Functional annotation using RPSblast analysis identified conserved protein domains in the conceptually translated gene index and assigned GO terms to those database transcripts which had informative BlastX hits. Blast Score Ratio and SimiTri analysis compared the conceptual transcriptome of the R. microplus database to other eukaryotic proteomes and EST databases, including those from 3 ticks. The most abundant protein domains in BmiGI2 were also analyzed by SimiTri methodology. Conclusions: These results indicate that a large fraction of BmiGI entries have no homologs in other sequenced genomes. This highlights the important insights in tick biology which are likely to result from a tick genome sequencing project. Sets of genes were identified which had closer homologues to mammalian genes than to insect genes. Members of these groups would likely be poor choices as targets for development of novel tick control technology.