Identification of four genes expressed by feeding, female Ixodes scapularis including three with sequence similarity to previously recognized genes

Abstract

We created a cDNA library from feeding, female Ixodes scapularis ticks and screened the library with a subtracted probe to eliminate most genes common to feeding female and mating male I. scapularis ticks. Four unique genes were identified in this screen. One gene, Is 9, (represented by 16 cDNAs) was more highly expressed in female ticks. This gene encodes a putative glycine-rich protein, which matched a number of glycine-rich proteins including attachment cement proteins from Rhipicephalus appendiculatus. A second gene, Is 10 (represented by one cDNA) was also more highly expressed in female ticks, but did not match any other sequences in the GenBank database. The third gene, Is 11 (represented by one cDNA) was very similar to Drosophila sp. hsp68 and hsp70 genes and was expressed about equally in male and female ticks. The fourth gene, Is 12 (represented by two cDNAs) was also about equally expressed in male and female ticks, and was similar to a salivary gland gene from Ixodes ricinis. This gene also showed limited similarity to some cuticle genes from insects.

The role of saliva in tick feeding

“…Several of these metastriate cement proteins have been characterized and shown to be immunogenic, and were proposed as vaccine candidates [294-299]. On the other hand, the Ixodes genus contains a large expansion of collagen-like smaller peptides, rich in proline and possibly hydroxyl-proline, as previously noted [238, 286, 300, 301]. …”

Environmental stresses induce the expression of putative glycine‐rich insect cuticular protein genes in adult Leptinotarsa decemlineata (Say)

“…They are found in a wide variety of organisms from prokaryotes to eukaryotes. The proteins share few conserved domains except for a number of short glycine-rich repeats (Mathelin et al ., 1995;Ruiter et al ., 1997;Guilfoile & Packila, 2004), making their classification into one family questionable (Sachetto-Martins et al ., 2000). Insect and spider silk proteins, elastin and collagen proteins also belong to this category (Xu & Lewis, 1990;Qin & Waite, 1998;Zhong et al ., 2006).…”

Molecular cloning of a small heat shock protein (sHSPII) from the cattle tick Rhipicephalus (Boophilus) annulatus salivary gland

“…Considering that the feeding process in ticks is associated with a rise in temperature [49]; and that accumulation of HSPs results in thermotolerance, which is the "cell's ability to withstand an otherwise lethal thermal challenge" [50], the role of sHSP as molecular chaperone in tick salivary gland can easily be predicted; they may act to confer protection to the whole organism or to the salivary glands in particular in order to withstand the increase in temperature and other stresses following ingestion of the blood meal. This assumption supports Xu et al [21] observation of the specific upregulation of a salivary sHSP of I. scapularis tick during engorgement called FTSP-5 [21].…”