An updated catalogue of salivary gland transcripts in the adult female mosquito, Anopheles gambiae

Salivary glands of blood-sucking arthropods contain a variety of compounds that prevent platelet and clotting functions and modify inflammatory and immunological reactions in the vertebrate host. In mosquitoes, only the adult female takes blood meals, while both sexes take sugar meals. With the recent description of the Anopheles gambiae genome, and with a set of similar to 3000 expressed sequence tags from a salivary gland cDNA library from adult female mosquitoes, we attempted a comprehensive description of the salivary transcriptome of this most important vector of malaria transmission. In addition to many transcripts associated with housekeeping functions, we found an active transposable element, a set of Wolbachia-like proteins, several transcription factors, including Forkhead, Hairy and doublesex, extracellular matrix components and 71 genes coding for putative secreted proteins. Fourteen of these 71 proteins had matching Edman degradation sequences obtained from SDS-PAGE experiments. Overall, 33 transcripts are reported for the first time as coding for salivary proteins. The tissue and sex specificity of these protein-coding transcripts were analyzed by RT-PCR and microarray experiments for insight into their possible function. Notably, two gene products appeared to be differentially spliced in the adult female salivary glands, whereas 13 contigs matched predicted intronic regions and may include additional alternatively spliced transcripts. Most An. gambiae salivary proteins represent novel protein families of unknown function, potentially coding for pharmacologically or microbiologically active substances. Supplemental data to this work can be found at http:// www.ncbi.nlm.nih.gov/projects/omes/index.html#Ag2.