An insight into the sialome of the frog biting fly, Corethrella appendiculata

• The first sialotranscriptome of a biting midge is described.
• Over 150 million 100 nt Illumina reads were assembled into 8943 coding sequences.
• Over 5000 coding sequences have been deposited to GenBank.
• The revealed salivary composition is quite complex.
• Results illuminate the evolution of bloodfeeding within the bloodfeeding Nematocera.

The Nematocera infraorder Culicomorpha is believed to have descended from bloodfeeding ancestors over 200 million years ago, generating bloodfeeding and non-bloodfeeding flies in two superfamilies, the Culicoidea—containing the mosquitoes, the frog-feeding midges, the Chaoboridae, and the Dixidae—and the Chironomoidea—containing the black flies, the ceratopogonids, the Chironomidae, and the Thaumaleidae. Bloodfeeding requires many adaptations, including development of a sophisticated salivary potion that disarms host hemostasis, the physiologic mechanism comprising platelet aggregation, vasoconstriction, and blood clotting. The composition of the sialome (from the Greek sialo = saliva) from bloodfeeding animals can be inferred from analysis of their salivary gland transcriptome. While members of the mosquitoes, black flies, and biting midges have provided sialotranscriptome descriptions, no species of the frog-biting midges has been thus analyzed. We describe in this work the sialotranscriptome of Corethrella appendiculata, revealing a complex potion of enzymes, classical nematoceran protein families involved in bloodfeeding, and novel protein families unique to this species of frog-feeding fly. Bacterial (Wolbachia) and novel viral sequences were also discovered.

The genus Corethrella contains the frog feeding midges that are the oldest relatives of the bloodfeeding Culicomorpha, including mosquitoes, black flies and cerapotogonida. We here describe the sialotranscriptome of C. appendiculata.Figure optionsDownload high-quality image (132 K)Download as PowerPoint slide