Culex tarsalis is a major vector of West Nile Virus (WNV) in North America. Although the genome for this species was recently sequenced, the physical genome map has not developed. Unlike other Culex species, that have sex-determination locus on chromosome 1, the sex locus in Cx. tarsalis is located on chromosome 3, the longest chromosome. It is currently unknown if this difference is associated with chromosomal rearrangements. The objectives of this study were to develop a high-resolution map for the precise physical genome mapping in Cx. tarsalis and to compare mitotic chromosomes between three species of Culicinae mosquitoes. Using mitotic chromosomes from imaginal discs of 4th instar larvae of Cx. tarsalis, we developed idiograms based on morphology and proportions of the mitotic chromosomes. In addition, the physical mapping of ribosomal genes using fluorescence in situ hybridization was performed.
The comparative analysis of Cx. tarsalis to Cx. pipiens and Cx. quinquefasciatus chromosomes showed that the total chromosome length in Cx. tarsalis is longer than the other two species suggesting the bigger genome size in this mosquito. A comparison of the relative chromosome length between the species indicated no significant differences suggesting that no large chromosomal translocation occurred between the species. Comparisons of the centromeric indexes demonstrated a significant difference in chromosome 1 between Cx. pipiens and Cx. quinquefasciatus. This difference suggests the presence of pericentric inversion between the species or amplification of ribosomal genes in Cx. pipiens. Studying mosquito chromosomes advances our understanding of Culex cytogenetics. Further comparative physical mapping of the three major mosquito genera will help us to understand the evolution of genus Culex better and to develop genome-based strategies for the vector control. / Master of Science in Life Sciences / West Nile Virus (WNV) is the most common virus transmitted to humans by mosquitoes in the United States. While many species of mosquitoes are known to carry WNV, Culex tarsalis is a major vector on the west coast of North America. However, previous research on Cx. tarsalis lack chromosome studies on this mosquito. Our study aims to develop a high-quality chromosome map for Cx. tarsalis and to compare the mitotic chromosomes of Cx. tarsalis and Cx. quinquefasciatus and Cx. pipiens in respect of chromosomal rearrangements. We used a fluorescent DNA probe to find the location of the ribosomal locus in the chromosomes of Cx. tarsalis. This study developed a cytogenetic tool for further genomic studies of Cx. tarsalis that will help to develop genome-based strategies for vector control. Comparing the physical mapping of the three major mosquito genera will help to understand the genome evolution in Culicinae mosquitoes better.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/98847 |
| Date | 12 June 2020 |
| Creators | Little, Chantelle Jenae |
| Contributors | Entomology, Sharakhova, Maria V., Auguste, Albert J., Sharakhov, Igor V. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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