A molecular study on the salivary glands of the African malaria vector Anopheles gambiae.

We report here the results of a molecular study initiated a few years ago with the objective to get some insights into the function of the Anopheles gambiae salivary glands, an organ that is relevant both for its role in pathogen transmission and for mosquito adaptation to hematophagy. Using the Signal Sequence Trap (SST) technique we could identify several salivary gland-specific cDNAs. Among these the putative An. gambiae apyrase and a family of D7-related genes have been analyzed in more detail. A fragment of ~800 bp in length, adjacent to the 5’ end of the apyrase coding region, was capable to confer salivary gland-specific expression to a LacZ reporter gene in transgenic D. melanogaster. This promoter may prove useful to drive gene expression into the salivary glands of transgenic anopheline mosquitoes. We have also characterized four D7-related genes that are abundantly expressed in adult female glands and are clustered in a region of approximately 7 Kb. Their function is still unclear, however, both the redundancy and the pattern of expression suggest that they are likely involved in blood feeding. The weak similarity to members of insects pheromone- and odorant-binding protein family suggests that the D7-related may bind and/or carry small hydrophobic ligands. Finally, we have started, more recently, a new round of SST screening and we have identified several additional salivary gland cDNAs whose characterization is currently in progress.