De novo sequencing, assembly and annotation of the Culicoides sonorensis genome.

The use of the new genomic technologies has led to major advances in control of several arboviruses of medical importance. However, the development of tools and resources available for vectors of non-zoonotic arboviruses remains neglected. Biting midges of the genus Culicoides transmit some of the most important arboviruses of wildlife and livestock worldwide, with a global impact on economic productivity, health and welfare. The absence of a suitable reference genome has hindered genomic analyses to date in this important group of vectors. In the present study, the genome of Culicoides sonorensis, a vector of bluetongue virus (BTV) in the USA, has been sequenced to be used as reference genome for transcriptomic analyses of vector competence for BTV. Results: The genome has a size of 197.4 Mb and has been assembled in 7,974 scaffolds. Its annotation using the transcriptomic data has identified 15,629 genes. Gene expression analyses of C. sonorensis females infected with BTV have identified 165 genes that were differentially expressed between vector competent and refractory females. Two candidate genes, glutathione S-transferase (gst) and the antiviral helicase ski2, were previously recognized as involved in vector competence for BTV in C. sonorensis (gst) and repressing dsRNA virus propagation (ski2). Conclusions: The genome of C. sonorensis has enabled preliminary analyses of the genetic profiles of vector competent and refractory individuals. The C. sonorensis genome and transcriptomes generated in this study provide suitable platforms for future research on arbovirus transmission. They will be a valuable source of comparative data for other important Dipteran vector families including mosquitoes (Culicidae) and sandflies (Psychodidae).