Whole genome assembly of Culex tarsalis

Abstract

The mosquito, Culex tarsalis, is a key vector in the western United States due to its role in transmission of zoonotic arboviruses that affect human health. Extensive research has been conducted on Cx. tarsalis ecology, feeding behavior, vector competence, autogeny, diapause, genetics, and insecticide resistance. Population genetic analyses in the western U.S. have identified at least three genetic clusters that are geographically distinct. Salivary gland-specific gene expression has also revealed genes involved in blood feeding. However, genetic studies of this mosquito have been hindered by the lack of a reference genome. To facilitate genomic studies in Cx. tarsalis, we have assembled and annotated a reference genome (CtarK1) based on PacBio HiFi reads from a single male. Using the Cx. tarsalis transcriptome and protein sequences from Culex quinquefasciatus, approximately 17,456 protein-coding genes, including the para insecticide resistance gene, were annotated in the CtarK1 genome. Genome completeness was assessed using the Benchmarking Universal Single-Copy Orthologs (BUSCO) tool, which identified 84.8% of the 2799 Dipteran BUSCO genes. The CtarK1 assembly is 790Mb with an N50 of 58kb. Using full mitochondrial genome alignments with other sequenced mosquito genomes we present a Bayesian phylogeny, which estimates that the divergence of Cx. tarsalis from Culex quinquefasciatus, the most closely related mosquito species with a genome, occurred 15.8-22.2 million years ago.