The sialotranscriptome of Antricola delacruzi female ticks is compatible with non-hematophagous behavior and an alternative source of food

Abstract

The hosts for Antricola delacruzi ticks are insectivorous, cave-dwelling bats on which only larvae are found. The mouthparts of nymphal and adult A. delacruzi are compatible with scavenging feeding because the hypostome is small and toothless. How a single blood meal of a larva provides energy for several molts as well as for oviposition by females is not known. Adults of A. delacruzi possibly feed upon an unknown food source in bat guano, a substrate on which nymphal and adult stages are always found. Guano produced by insectivorous bats contains twice the amount of protein and 60 times the amount of iron as beef. In addition, bacteria and chitin-rich fungi proliferate on guano. Comparative data on the transcriptome of the salivary glands of A. delacruzi is nonexistent and would help to understand the physiological adaptations of salivary glands that accompany different sources of food as well as the steps taken by the Acari toward haematophagy, believed to have evolved from scavenging dead animals. Annotation of the transcriptome of salivary glands from female instars of A. delacruzi collected on guano categorized 5.7% of the clusters of expressed genes as putative secreted proteins. They included abundantly expressed TIL-domain-containing proteins (possible anti-microbials), an abundantly expressed protein similar to a serum amyloid found in the sialotranscriptomes of Ornithodoros spp., a savignygrin, a family of mucin/peritrophin/cuticle-like proteins, anti-microbials and an HIV envelope-like glycoprotein also found in soft ticks. When comparing the transcriptome of A. delacruzi with those of blood-feeding female soft and hard ticks some notable differences were observed; they consisted of the following transcripts over- or under-represented or absent in the sialotranscriptome of A. delacruzi that may reflect its source of food: ferritin, mucins with chitin-binding domains and TIL-domain-containing proteins versus lipocalins, basic tail proteins, metalloproteases, glycine-rich proteins and Kunitz protease inhibitors, respectively.

Figure 1

A heat map of the most abundantly expressed transcripts in A. delacruzi females and of the most abundantly expressed transcripts in hematophagous female ticks of genes encoding putative inhibitors of proteins involved in host homeostasis. Data is derived from non-normalized cDNA libraries constructed with the same methodology employed for the A. delacruzi library.

Figure 2

Tick TIL domain-containing proteins. (A) Clustal alignment. Symbols over the figure indicate (*) Amino acid identity, (:) similarity and (.) less similarity. (B) bootstrapped phylogram (10,000 iterations) of the alignment in (A). Sequences deposited at NCBI are represented by six capital letters deriving from the genus and species name followed by their GenBank accession number. Remaining sequences were derived from analysis of publicly available EST’s and described in a previous review (Francischetti et al. 2009). Values near nodes indicate bootstrap support above 50%. Smaller values are not represented. The bar at the bottom indicates 10% amino acid divergence. Species related to acronyms for naming sequences used to construct the alignment and phylogram are: ORNCOR, O. coriaceus; Ant: A. delacruzi; HYAMAR: Hyalomma marginatum; Rh micro: R. microplus; Amb var: Amblyomma variegatum; Rh ap: R. appendiculatus; and Der: Dermacentor andersoni; IXOSCA: I scapularis.

Figure 2

Tick TIL domain-containing proteins. (A) Clustal alignment. Symbols over the figure indicate (*) Amino acid identity, (:) similarity and (.) less similarity. (B) bootstrapped phylogram (10,000 iterations) of the alignment in (A). Sequences deposited at NCBI are represented by six capital letters deriving from the genus and species name followed by their GenBank accession number. Remaining sequences were derived from analysis of publicly available EST’s and described in a previous review (Francischetti et al. 2009). Values near nodes indicate bootstrap support above 50%. Smaller values are not represented. The bar at the bottom indicates 10% amino acid divergence. Species related to acronyms for naming sequences used to construct the alignment and phylogram are: ORNCOR, O. coriaceus; Ant: A. delacruzi; HYAMAR: Hyalomma marginatum; Rh micro: R. microplus; Amb var: Amblyomma variegatum; Rh ap: R. appendiculatus; and Der: Dermacentor andersoni; IXOSCA: I scapularis.

Figure 3

Tick amyloid salivary secreted protein family, with 15 ESTs on Anticolas delacruzi. (A) Clustal alignment. (B) Bootstrapped phylogram. For other information, see Figure 1. Species related to acronyms for naming sequences used to construct phylogram are: ORNPAR, O. parkeri; Ant: A. delacruzi; Rh micro: R. microplus; IXOSCA: I scapularis; and Der: Dermacentor andersoni.

Figure 3

Tick amyloid salivary secreted protein family, with 15 ESTs on Anticolas delacruzi. (A) Clustal alignment. (B) Bootstrapped phylogram. For other information, see Figure 1. Species related to acronyms for naming sequences used to construct phylogram are: ORNPAR, O. parkeri; Ant: A. delacruzi; Rh micro: R. microplus; IXOSCA: I scapularis; and Der: Dermacentor andersoni.

Figure 4

Conserved tick salivary secreted protein family, similar to HIV env glycoprotein, with 7 ESTs in Antricola delacruzi. (A) Clustal alignment. (B) Bootstrapped phylogram. For other information, see Figure 1. Species related to acronyms for naming sequences used to construct phylogram are: Ant: A. delacruzi; ORNPAR, O. parkeri; Amby am: Amblyomma americanum; Rh ap: R appendiculatus; Rh micro: R. microplus; IXOSCA: I scapularis.

Figure 4

Conserved tick salivary secreted protein family, similar to HIV env glycoprotein, with 7 ESTs in Antricola delacruzi. (A) Clustal alignment. (B) Bootstrapped phylogram. For other information, see Figure 1. Species related to acronyms for naming sequences used to construct phylogram are: Ant: A. delacruzi; ORNPAR, O. parkeri; Amby am: Amblyomma americanum; Rh ap: R appendiculatus; Rh micro: R. microplus; IXOSCA: I scapularis.