The expression of genes coding for distinct types of glycine-rich proteins varies according to the biology of three metastriate ticks, Rhipicephalus (Boophilus) microplus, Rhipicephalus sanguineus and Amblyomma cajennense

Abstract

BackgroundTicks secrete a cement cone composed of many salivary proteins, some of which are rich in the amino acid glycine in order to attach to their hosts' skin. Glycine-rich proteins (GRPs) are a large family of heterogeneous proteins that have different functions and features; noteworthy are their adhesive and tensile characteristics. These properties may be essential for successful attachment of the metastriate ticks to the host and the prolonged feeding necessary for engorgement. In this work, we analyzed Expressed Sequence Tags (ESTs) similar to GRPs from cDNA libraries constructed from salivary glands of adult female ticks representing three hard, metastriate species in order to verify if their expression correlated with biological differences such as the numbers of hosts ticks feed on during their parasitic life cycle, whether one (monoxenous parasite) or two or more (heteroxenous parasite), and the anatomy of their mouthparts, whether short (Brevirostrata) or long (Longirostrata). These ticks were the monoxenous Brevirostrata tick, Rhipicephalus (Boophilus) microplus, a heteroxenous Brevirostrata tick, Rhipicephalus sanguineus, and a heteroxenous Longirostrata tick, Amblyomma cajennense. To further investigate this relationship, we conducted phylogenetic analyses using sequences of GRPs from these ticks as well as from other species of Brevirostrata and Longirostrata ticks.ResultscDNA libraries from salivary glands of the monoxenous tick, R. microplus, contained more contigs of glycine-rich proteins than the two representatives of heteroxenous ticks, R. sanguineus and A. cajennense (33 versus, respectively, 16 and 11). Transcripts of ESTs encoding GRPs were significantly more numerous in the salivary glands of the two Brevirostrata species when compared to the number of transcripts in the Longirostrata tick. The salivary gland libraries from Brevirostrata ticks contained numerous contigs significantly similar to silks of true spiders (17 and 8 in, respectively, R. microplus and R. sanguineus), whereas the Longirostrata tick contained only 4 contigs. The phylogenetic analyses of GRPs from various species of ticks showed that distinct clades encoding proteins with different biochemical properties are represented among species according to their biology.ConclusionsWe found that different species of ticks rely on different types and amounts of GRPs in order to attach and feed on their hosts. Metastriate ticks with short mouthparts express more transcripts of GRPs than a tick with long mouthparts and the tick that feeds on a single host during its life cycle contain a greater variety of these proteins than ticks that feed on several hosts.

An insight into the sialome of Hyalomma excavatum

“…Enzymes accounted for 7.8% of the reads, metalloproteases of the reprolysin family (Francischetti et al, 2003, 2005) accruing the majority of these reads. Glycine rich proteins, associated with glue proteins (Bishop et al, 2002; Maruyama et al, 2010) acquired 16% of the S class reads. Contigs coding for protease inhibitor domains collected 21 % of the reads, 4.6 % from single domain Kunitz proteins (Francischetti et al, 2009) and 13.6% from members of the Madanin anti-thrombin peptide family (Nakajima et al, 2006).…”

De novo assembly and annotation of the salivary gland transcriptome of Rhipicephalus appendiculatus male and female ticks during blood feeding

“…Amblyomma (Longirostrata ticks), on the other hand, have longer mouthparts that penetrate the skin more deeply, requiring a smaller cement-cone to facilitate adhesion. Indeed, Maruyama et al (2010) found that ticks with short mouthparts expressed elevated levels of Glycine rich transcripts when compared to ticks with long mouthparts. Interestingly, a larger abundance of Glycine rich transcripts was observed in the male compared to female R. appendiculatus transcriptomes, a finding also observed in R.…”

Tick attachment cement – reviewing the mysteries of a biological skin plug system

“…64P) were identified, steering research towards anti‐tick vaccines (Mulenga et al ., 1999; Bishop et al ., 2002; Trimnell, Hails, & Nuttall, 2002; Trimnell et al ., 2005; Zhou et al ., 2006). The establishment of complementary DNA (cDNA) libraries allowed the comparison of putative cement proteins in different tick species showing the variety in salivary gland composition (Maruyama et al ., 2010). Nevertheless it became clear that the sheer quantity of proteins and other products of the salivary glands (Alarcon‐Chaidez, 2014) make assignment to particular functions such as cement formation difficult.…”

“…Similarly, one‐host ticks, which spend most of their life attached to the host, might produce larger quantities of these proteins. The identification of nucleotide sequences which encode potential GRPs from cDNA libraries of three different tick species [ Amblyomma cajennense (Fabricius, 1787), Rhipicephalus microplus , R. sanguineus ] seems to confirm these suggestions (Maruyama et al ., 2010). However, GRPs may have other functions: they are also found in antimicrobial substances and are related to immune evasion (Francischetti et al ., 2009; Havlikova et al ., 2009).…”

“…However, GRPs may have other functions: they are also found in antimicrobial substances and are related to immune evasion (Francischetti et al ., 2009; Havlikova et al ., 2009). Proteins of this class are also found in the family Argasidae (Maruyama et al ., 2010), which do not produce cement. Additionally, some GRPs in tick saliva are shorter than proteins usually involved in animal adhesives such as spider silk (Bullard et al ., 2016).…”