Authors: Chian Teng Ong, Manuel Rodriguez-Valle, Ala Lew-Tabor
Ixodes holocyclus is the paralysis tick commonly found in Australia. I. holocyclus does not cause paralysis in the primary host – bandicoots, but markedly affects secondary hosts such as companion animals, livestock and humans. Holocyclotoxins are the neurotoxin molecules in I. holocyclus responsible for paralysis symptoms. There is limited understanding on holocyclotoxins due to the difficulties in purifying and expressing this toxin in vitro. For the first time, next-generation sequencing technologies were utilised to generate transcriptome data from four cDNA samples – viscera and salivary glands samples collected from female adult ticks engorged on paralysed companion animals, salivary glands sample collected from female adult ticks engorged on bandicoots and a sample from unfed female adult ticks. Contig-encoded proteins in each library were annotated according to their best BLAST match against several databases and functionally assigned into six categories - housekeeping proteins, transposable elements, pathogen-related proteins, hypothetical proteins, secreted proteins and novel proteins. The “secreted protein” category is comprised of ten protein families – enzymes, protease inhibitors, antigens, mucins, immunity-related proteins, lipocalins, glycine-rich proteins, putative secreted proteins, salivary proteins and toxin-like proteins. Comparisons of contig representation between the four libraries reveal the differential expressions of tick proteins under different feeding conditions: developmental stages and hosts. A comparison between I. scapularis proteins and I. holocyclus transcripts revealed that approximately 50% of I. holocyclus transcripts are unique to I. holocyclus.
Keywords: Ixodes holocyclus, paralysis tick, trancriptome, functionally annotation