Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2004
Publication Date: 4/1/2005
Citation: Campbell, C.L., Vandyke, K., Letchworth III, G.J., Drolet, B.S., Hanekamp, T., Wilson, W.C. 2005. Midgut and salivary gland transcriptomes of the arbovirus vector culicoides sonorensis (diptera: ceratopogonidae). Insect Molecular Biology. 14(2):121-136. Interpretive Summary: Culicoides sonorensis is a biting midge that transmits virus (bluetongue and epizootic hemorrhagic disease virus) diseases to animals, such as cows and deer. The only time that these viruses are transmitted to animals is through an insect bite. Thus the insects are referred to as disease vectors. The insects pick up the virus by biting an infected host animal. Before the virus can be transferred to a new host animal, the virus must first successfully infect the vector insect and move from the initial infection site, the gut, to the salivary glands for a subsequent bite. For this reason, we are especially interested in learning how the virus infects the insect gut. Some scientists postulate that variations in the insect's ability to be infected with a virus and then transmit it to another animal host may be caused by either differences in the environment or genetic differences between individual insects. It is also possible that a combination of these two factors play a part in whether an individual insect can successfully transmit the virus. Increased knowledge about the insect gut and how the virus invades and grows in it will make it possible to devise ways to prevent virus spread to the salivary glands. For these reasons, we have chosen to sequence and catalog expressed genes (cDNAs) from the midgut and salivary tissues of this biting midge. This sequence information will provide us with new tools that will be useful for a variety of purposes, from evolutionary comparisons with other disease vector insects to functional studies to determine the roles played by genes enabling the spread of viruses. We chose to generate a high volume, low quality sequence collection. These are known as expressed sequence tags or ESTs. Of 1719 ESTs from adult serum-fed female midguts harvested within 5 hours of feeding, 356 clusters of serine proteases were produced. Of 708 salivary gland ESTs analyzed, clusters representing two new classes of gene families were identified, as well as other genes that may effect the host immune system during blood-feeding.
Technical Abstract: Transcriptome information from midguts and salivary glands of adult female Culicoides sonorensis provides new insight into vector biology. Of 1719 expressed sequence tags (ESTs) from adult serum-fed female midguts harvested within 5 hours of feeding, 356 clusters of serine proteases were produced. Of 708 salivary gland ESTs analyzed, clusters representing two new classes of gene families were identified: a new class of D7-related cDNAs and a new class of kunitz-like domain protease inhibitors. In addition, other putative immunomodulatory cDNAs were isolated: 5' nucleotidases, hyaluronidase-like cDNAs, a coagulation inhibitor-like cDNA, antigen 5-related proteins, and a platelet-activating factor acetylhydrolase.