Comparative microarray analysis of 'Rhipicephalus (Boophilus) microplus' expression profiles of larvae pre-attachment and feeding adult female stage on 'Bos indicus' and 'Bos taurus' cattle

Background: 'Rhipicephalus (Boophilus) microplus' is an obligate blood feeder which is host specific to cattle. Existing knowledge pertaining to the host or host breed effects on tick transcript expression profiles during the tick - host interaction is poor. Results: Global analysis of gene expression changes in whole 'R. microplus' ticks during larval, pre-attachment and early adult stages feeding on 'Bos indicus' and 'Bos taurus' cattle were compared using gene expression microarray analysis. Among the 13,601 'R. microplus' transcripts from BmiGI Version 2 we identified 297 high and 17 low expressed transcripts that were significantly differentially expressed between 'R. microplus' feeding on tick resistant cattle ['Bos indicus' (Brahman)] compared to 'R. microplus' feeding on tick susceptible cattle ['Bos taurus' (Holstein-Friesian)] (p ≤ 0.001). These include genes encoding enzymes involved in primary metabolism, and genes related to stress, defence, cell wall modification, cellular signaling, receptor, and cuticle formation. Microarrays were validated by qRT-PCR analysis of selected transcripts using three housekeeping genes as normalization controls. Conclusion: The analysis of all tick stages under survey suggested a coordinated regulation of defence proteins, proteases and protease inhibitors to achieve successful attachment and survival of 'R. microplus' on different host breeds, particularly 'Bos indicus' cattle. 'R. microplus' ticks demonstrate different transcript expression patterns when they encounter tick resistant and susceptible breeds of cattle. In this study we provide the first transcriptome evidence demonstrating the influence of tick resistant and susceptible cattle breeds on transcript expression patterns and the molecular physiology of ticks during host attachment and feeding. The microarray data used in this analysis have been submitted to NCBI GEO database under accession number GSE20605 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE20605.