Gene Expression in the Salivary Gland of Rhipicephalus (Boophilus) microplus Fed on Tick-Susceptible and Tick-Resistant Hosts

Abstract

The success of cattle tick fixation largely depends on the secretion of substances that alter the immune response of the host. The majority of these substances are expressed by the parasite salivary gland and secreted in tick saliva. It is known that hosts can mount immune responses against ticks and bovine European breeds, and bovine industrial crossbreeds are more susceptible to infestations than are Bos indicus cattle. To identify candidates for the development of novel control strategies for the cattle tick Rhipicephalus (Boophilus) microplus, a salivary gland transcriptome analysis of engorged females fed on susceptible or resistant hosts was performed. Using RNA-Seq, transcriptomes were de novo assembled and produced a total of 235,451 contigs with 93.3% transcriptome completeness. Differential expression analysis identified 137 sequences as differentially expressed genes (DEGs) between ticks raised on tick-susceptible or tick-resistant cattle. DEGs predicted to be secreted proteins include innexins, which are transmembrane proteins that form gap junction channels; the transporters Na + /dicarboxylate, Na + /tricarboxylate, and phosphate transporter and a putative monocarboxylate transporter; a phosphoinositol 4-phosphate adaptor protein; a cysteine-rich protein containing a trypsin inhibitor-like (TIL) domain; a putative defense protein 3 containing a reeler domain; and an F-actin-uncapping protein LRRC16A with a CARMIL_C domain; these genes were upregulated in ticks fed on tick-susceptible cattle. DEGs predicted to be non-secreted proteins included a small heat shock protein and the negative elongation factor B-like, both acting in a coordinated manner to increase HSP transcript levels in the salivary glands of the ticks fed on tick-susceptible cattle; the 26S protease regulatory subunit 6B and another chaperone with similarity to calnexin, also upregulated in ticks fed on tick-susceptible cattle; an EF-hand calcium binding protein and a serine carboxypeptidase (SCP), both involved in the blood coagulation cascade and upregulated in ticks fed on tick-susceptible cattle; and two ribosomal proteins, the 60S acidic ribosomal protein P2 and the 60S ribosomal protein L19. These results help to characterize cattle tick salivary gland gene expression in tick-susceptible and tick-resistant hosts and suggest new putative targets for the control of tick infestations, as those genes involved in the mechanism of stress response during blood feeding.

RNA-seq analysis and gene expression dynamics in the salivary glands of the argasid tick Ornithodoros erraticus along the trophogonic cycle

“…In ticks, metalloproteases have been found in the midgut, ovary, salivary glands and saliva, where they are particularly abundant and diverse [ 45 , 86 , 97 ]. Tick salivary metalloproteases play functions related to blood-feeding and modulation of the host defensive responses, including degradation of extracellular matrix proteins at the bite site to form the feeding pool and degradation of fibrinogen and fibrin, thereby preventing blood coagulation, degradation of inflammatory mediators and inhibition of host tissue repair via anti-angiogenic activity [ 41 , 92 , 97 – 99 ]. Not surprisingly, metalloproteases were the enzyme class most abundantly represented in the O. erraticus sialotranscriptome (338 transcripts) (Table 4 ), in parallel with that also reported for other tick sialomes [ 29 , 39 , 41 , 43 , 93 , 98 ].…”

“…The family of TIL-domain inhibitors includes chymotrypsin, elastase and trypsin inhibitors, which are ubiquitous in blood-feeding insects and tick sialomes. Some members of this family are known to interfere with the host inflammatory response and others have been characterised as antimicrobial peptides [ 99 ]. Kazal domain inhibitors are less frequent in tick sialomes and their function remains unknown [ 45 , 109 ].…”

Quantitative Visions of Reality at the Tick-Host Interface: Biochemistry, Genomics, Proteomics, and Transcriptomics as Measures of Complete Inventories of the Tick Sialoverse

“…Giachetto et al ( 2020 ) generated salivary gland transcriptomes for engorged female R. microplus that was fed on tick-resistant or tick-susceptible hosts. The transcriptome was assembled from 74,639,552 reads (holstein cattle) and 63,013,658 reads (crossbreed cattle) resulting in 235,451 contigs.…”

Characterization of the Rhipicephalus (Boophilus) microplus Sialotranscriptome Profile in Response to Theileria equi Infection

“…Proteins containing a reeler domain were described in a manifold of studies involved in the tick’s innate immunity. Previous investigations indicate the participation of this protein in the Bombyx mori melanization cascade, and it is also reported as a defense response against the viruses in whiteflies of the Bemisia tabaci species complex [ 49 , 50 ]. Apart from insects, there is a study reporting protein with a reeler domain favoring the colonization of Borrelia burgdorferi in gut cells of Ixodes scapularis [ 51 ].…”