Abstract
BackgroundAn initial comparative genomic study of the malaria vector Anopheles gambiae and the yellow fever mosquito Aedes aegypti revealed striking differences in the genome assembly size and in the abundance of transposable elements between the two species. However, the chromosome arms homology between An. gambiae and Ae. aegypti, as well as the distribution of genes and repetitive elements in chromosomes of Ae. aegypti, remained largely unexplored because of the lack of a detailed physical genome map for the yellow fever mosquito.ResultsUsing a molecular landmark-guided fluorescent in situ hybridization approach, we mapped 624 Mb of the Ae. aegypti genome to mitotic chromosomes. We used this map to analyze the distribution of genes, tandem repeats and transposable elements along the chromosomes and to explore the patterns of chromosome homology and rearrangements between Ae. aegypti and An. gambiae. The study demonstrated that the q arm of the sex-determining chromosome 1 had the lowest gene content and the highest density of minisatellites. A comparative genomic analysis with An. gambiae determined that the previously proposed whole-arm synteny is not fully preserved; a number of pericentric inversions have occurred between the two species. The sex-determining chromosome 1 had a higher rate of genome rearrangements than observed in autosomes 2 and 3 of Ae. aegypti.ConclusionsThe study developed a physical map of 45% of the Ae. aegypti genome and provided new insights into genomic composition and evolution of Ae. aegypti chromosomes. Our data suggest that minisatellites rather than transposable elements played a major role in rapid evolution of chromosome 1 in the Aedes lineage. The research tools and information generated by this study contribute to a more complete understanding of the genome organization and evolution in mosquitoes.
Highlights
An initial comparative genomic study of the malaria vector Anopheles gambiae and the yellow fever mosquito Aedes aegypti revealed striking differences in the genome assembly size and in the abundance of transposable elements between the two species
A physical map of the Ae. aegypti genome Our study developed a physical map of 45% of the Ae. aegypti genome using fluorescent in situ hybridization (FISH) with mitotic chromosomes from imaginal discs of fourth instar larvae (Figure 1)
This map guided the analyses of the genes, satellites and transposable element (TE) landscapes in the Ae. aegypti genome and provided important insights into chromosome evolution in mosquitoes
Summary
An initial comparative genomic study of the malaria vector Anopheles gambiae and the yellow fever mosquito Aedes aegypti revealed striking differences in the genome assembly size and in the abundance of transposable elements between the two species. The size of Ae. aegypti genome - 1,376 mega base pairs (Mb) - is the largest among other mosquito genomes sequenced so far It is five times bigger than the 264 Mb genome of An. gambiae. Cbanding studies located heterochromatin in centromeres of all chromosomes and in the intercalary region on the q arm of the homomorphic sex-determining chromosome 1 of Ae. aegypti [9,10,11], molecular characteristics of the heterochromatic regions in this species remain unclear
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