The salivary gland transcriptome of the neotropical malaria vector Anopheles darlingi reveals accelerated evolution of genes relevant to hematophagy

Abstract

BackgroundMosquito saliva, consisting of a mixture of dozens of proteins affecting vertebrate hemostasis and having sugar digestive and antimicrobial properties, helps both blood and sugar meal feeding. Culicine and anopheline mosquitoes diverged ~150 MYA, and within the anophelines, the New World species diverged from those of the Old World ~95 MYA. While the sialotranscriptome (from the Greek sialo, saliva) of several species of the Cellia subgenus of Anopheles has been described thoroughly, no detailed analysis of any New World anopheline has been done to date. Here we present and analyze data from a comprehensive salivary gland (SG) transcriptome of the neotropical malaria vector Anopheles darlingi (subgenus Nyssorhynchus).ResultsA total of 2,371 clones randomly selected from an adult female An. darlingi SG cDNA library were sequenced and used to assemble a database that yielded 966 clusters of related sequences, 739 of which were singletons. Primer extension experiments were performed in selected clones to further extend sequence coverage, allowing for the identification of 183 protein sequences, 114 of which code for putative secreted proteins.ConclusionComparative analysis of sialotranscriptomes of An. darlingi and An. gambiae reveals significant divergence of salivary proteins. On average, salivary proteins are only 53% identical, while housekeeping proteins are 86% identical between the two species. Furthermore, An. darlingi proteins were found that match culicine but not anopheline proteins, indicating loss or rapid evolution of these proteins in the old world Cellia subgenus. On the other hand, several well represented salivary protein families in old world anophelines are not expressed in An. darlingi.

The Salivary Gland Transcriptome of the Eastern Tree Hole Mosquito,Ochlerotatus triseriatus

“…aegypti predicted proteins (P < 0.001 Mann-Whitney rank sum test). This significant difference further supports the concept that the evolution of mosquito salivary secreted proteins occurs at a faster pace than H proteins (Valenzuela et al 2003, Calvo et al 2007a, 2009b.…”

“…These five sequences are consistent with the existence of two genes providing for alleles and splice variants. The multigene pattern has been observed previously for Aedes and Culex mosquitoes (Ribeiro et al 2004Arca et al 2007), whereas anophelines to date appear to have only one gene (Valenzuela et al 2003, Arca et al 2005, Calvo et al 2009b. One of the Aedes and one of the Anopheles proteins have been characterized as inhibitors of collagen-induced platelet aggregation by their strong interaction with collagen (Calvo et al 2007b, Yoshida et al 2008).…”

“…OT-547 codes for a peptide that is 57% identical to this Aedes protein, and weaker (<40%) identities to other proteins. Interestingly, OT-547 contains the block I-G-x(10)-G-x(2)-W-x(2)-G-x(5)-Ex(2)-R-R-x-F, which was deducted from alignment of anopheline proteins of the 6.2-kDa family described in previous sialotranscriptomes (Arca et al 2005, Calvo et al 2007a, 2009b. Alignment of OT-547 to the Aedes and anopheline sequences (Fig.…”

Detection of immunogenic proteins from Anopheles sundaicussalivary glands in the human serum

“…D7 proteins are also members of the odorant-binding protein superfamily (ODP) and are found in the salivary glands of blood-sucking insects, such as mosquitoes, sand flies, and Culicoides (26) . This protein has two types, i.e., the short form, which is only found in mosquitoes, and the long form, which can be found in mosquitoes and sand fl ies (23) (24) .…”

“…This protein has two types, i.e., the short form, which is only found in mosquitoes, and the long form, which can be found in mosquitoes and sand fl ies (23) (24) . D7 proteins have functions related to the binding of one or more agonists hemostasis and the blood feeding process (26) . Some D7 proteins, i.e., D7r1, D7r2, D7r3, D7r4, and long form D7, have been shown to bind with biogenic amines compounds, such as serotonin, histamine, and norepinephrine, thus becoming antagonistic to vasoconstrictors and affecting platelet aggregation and induction of pain (27) .…”