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Title: Evolutionary conserved microRNAs are ubiquitously expressed compared to tick-specific miRNAs in the cattle tick Rhipicephalus (Boophilus) microplus

Author
item BARRERO, ROBERTO - Murdoch University
item KEEBLE-GAGNERE, GABRIEL - Murdoch University
item ZHANG, BING - Queensland Department Of Primary Industries & Fisheries
item MOOLHUIJZEN, PAULA - Murdoch University
item IKEO, KAZUHO - Center For Information Biology And Dna Databank Of Japan
item TATENO, YOSHIO - Center For Information Biology And Dna Databank Of Japan
item GOJOBORI, TAKASHI - Center For Information Biology And Dna Databank Of Japan
item Guerrero, Felicito
item LEW-TABOR, ALA - Murdoch University
item BELLGARD, MATTHEW - Murdoch University

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2011
Publication Date: 6/24/2011
Citation: Barrero, R.A., Keeble-Gagnere, G., Zhang, B., Moolhuijzen, P., Ikeo, K., Tateno, Y., Gojobori, T., Guerrero, F., Lew-Tabor, A., Bellgard, M. 2011. Evolutionary conserved microRNAs are ubiquitously expressed compared to tick-specific miRNAs in the cattle tick Rhipicephalus (Boophilus) microplus. BMC Genomics. 12:Article 328.

Interpretive Summary: MicroRNAs (miRNAs) are small RNAs occuring in cells that do not code for functional proteins. Rather, they act as regulators of gene expression in eukaryotes, modulating a large diversity of biological processes. The discovery of miRNAs has provided new opportunities to understand the biology of a number of species. The cattle tick Rhipicephalus (Boophilus) microplus causes significant economical losses in cattle production worldwide and a better understanding of the molecular and biological processes in this tick would help the design of novel control methodologies. With this in mind, we utilized Illumina/Solexa next-generation sequencing technology to sequence the population of small RNAs derived from various tick life cycles stages and selected dissected tick organs. Overall we found 58 tick miRNAs with 33, 49 and 48 of these expressed in eggs, larvae and adult ticks, respectively. We also found 42, 41 and 38 miRNAs expressed in the female tick gut, salivary glands and ovaries, respectively. We found the major differences in miRNAs among our samples were seen in the quantitative levels of expression of the more abundant miRNAs. For example, the only previously known tick miRNA, called miR-9a, was expressed in all samples, but the highest level of expression was found in tick larvae exposed for six hours to a host animal. The most abundant tick miRNA found in this study is miR-1, particularly highly expressed in larval and adult stages as well as female gut and ovaries. In salivary glands we found a significant up regulation of let-7 and miR-275, making these miRNAs interesting targets for further studies. Findings presented in this study extend our knowledge of the biology and evolution of microRNAs in arthropods and should help elucidate regulatory metabolic pathways in this important agricultural pest.

Technical Abstract: MicroRNAs (miRNAs) are small non-coding RNAs that act as regulators of gene expression in eukaryotes modulating a large diversity of biological processes. The discovery of miRNAs has provided new opportunities to understand the biology of a number of species. The cattle tick Rhipicephalus (Boophilus) microplus causes significant economical losses in cattle production worldwide and the lack of an effective vaccine requires that several approaches be conducted to further understand their biology. To be able to provide new insights into the biology of cattle ticks and to expand the repertoire of tick miRNAs we utilized Illumina/Solexa technology to sequence the small RNA transcriptomes derived from various tick life cycles stages and selected organs. To discover and profile novel tick miRNAs we employed a comparative genomic approach identifying identical or nearly identical miRNAs conserved between cattle ticks and flies. Overall we found 58 tick miRNAs with 33, 49 and 48 of these expressed in eggs, larvae and adult ticks, respectively. We also found 42, 41 and 38 miRNAs expressed in the female tick gut, salivary glands and ovaries, respectively. The major differences in miRNA among samples results from differential expression levels of commonly expressed miRNAs. The only previously known tick miRNA, miR-9a, was found expressed in all samples sequenced in this study, but particularly up regulated in tick larvae exposed for six hours to their host. The most abundant tick miRNA found in this study is miR-1 particularly highly expressed in larval and adult stages as well as female gut and ovaries. In salivary glands we found a significant up regulation of let-7 and miR-275 making these miRNAs interesting targets for further functional studies. Findings presented in this study extend our knowledge of the biology and evolution of microRNAs in arthropods. The repertoire of tick microRNAs has been significantly expanded in this study and we envisage that these resources will facilitate functional annotation of the cattle tick genome and promote further functional and comparative genomics studies of small regulatory RNAs in arthropods.