Exploring the Transcriptomic Data of the Australian Paralysis Tick, Ixodes Holocyclus

Abstract

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 a limited understanding of
holocyclotoxins due to the difficulties in purifying and
expressing these toxins in vitro. Next-generation
sequencing technologies were utilised for the first time to
generate transcriptome data from two cDNA samples –
salivary glands samples collected from female adult ticks
engorged on paralysed companion animals and on
bandicoots. Contig-encoded proteins in each library
were annotated according to their best BLAST match
against several databases and functionally assigned into
six protein categories: housekeeping, transposable
elements, pathogen-related, hypothetical, secreted and
novel. The “secreted protein” category is comprised of
ten protein families: enzymes, protease inhibitors,
antigens, mucins, immunity-related, lipocalins, glycinerich,
putative secreted, salivary and toxin-like.
Comparisons of contig representation between the two
libraries reveal the differential expression of tick
proteins collected from different hosts. This study
provides a preliminary description of the I. holocyclus
tick salivary gland transcriptome.