Amblyomma aureolatum salivary and midgut transcriptome

Rickettsia rickettsii is a tick-borne obligate intracellular bacterium that causes Rocky Mountain Spotted Fever (RMSF). In Brazil, two species of ticks in the genera Amblyomma, A. sculptum and A. aureolatum, are incriminated as vectors of R. rickettsii. Importantly, these two species present remarkable differences in susceptibility to R. rickettsii infection, where A. aureolatum is more susceptible than A. sculptum.To explore the molecular factors responsible for those differences in susceptibility, ticks were fed on natural hosts previously inoculated with R. rickettsii, mimicking a natural infection. As control, ticks were fed on non-infected animals. Both midgut (MG) and salivary glands (SG) of all the A. sculptum and A. aureolatum ticks that were positive for infection were colonized by R. rickettsii. This result suggested that important factors for controlling the infection were produced in MG. Therefore, the total RNA extracted from MG of infected or control A. sculptum and A. aureolatum females was submitted to RNA sequencing (RNAseq). The majority of the genes of A. sculptum that were differentially expressed by infection were upregulated, whereas most of modulated genes of A. aureolatum were downregulated. The functional classes that comprises downregulated genes of A. aureolatum, for instance metabolism, signal transduction, protein modification, and extracellular matrix, also includes genes of A. sculptum that were upregulated by infection.