Diversity in the quantum sialome of ticks revealed by RNAseq of single tick salivary glands. Ixodes ricinus

Ticks salivate while feeding on their hosts. Saliva helps blood feeding by having host anti-hemostatic and immunomodulatory components. Previous transcriptomic and proteomic studies revealed the complexity of tick saliva, comprised of hundreds of polypeptides grouped in several multi-genic families such as lipocalins, Kunitz-domain containing peptides, metalloproteases and several other families uniquely found in ticks. These studies also revealed that the composition of saliva changes with time; transcripts from the same family wax and wane their expression as a function of feeding time. These previous studies were based on transcriptomes derived from pools of several organisms. To investigate the uniqueness of tick sialomes (from the Greek sialo=saliva), we performed transcriptomic analysis of individual adult female I. ricinus ticks (in triplicates) at three different times of feeding (24, 48 and 72 h). To investigate whether host factors could influence sialome switching, we also compared ticks fed on a rabbit with ticks artificially fed on defibrinated blood depleted of platelets and leukocytes, and with heat inactivated serum.