Genome sequence of the Asian Tiger mosquito, Aedes albopictus, reveals insights into its biology, genetics, and evolution

Abstract

The Asian tiger mosquito, Aedes albopictus, is a highly successful invasive species that transmits a number of human viral diseases, including dengue and Chikungunya fevers. This species has a large genome with significant population-based size variation. The complete genome sequence was determined for the Foshan strain, an established laboratory colony derived from wild mosquitoes from southeastern China, a region within the historical range of the origin of the species. The genome comprises 1,967 Mb, the largest mosquito genome sequenced to date, and its size results principally from an abundance of repetitive DNA classes. In addition, expansions of the numbers of members in gene families involved in insecticide-resistance mechanisms, diapause, sex determination, immunity, and olfaction also contribute to the larger size. Portions of integrated flavivirus-like genomes support a shared evolutionary history of association of these viruses with their vector. The large genome repertory may contribute to the adaptability and success of Ae. albopictus as an invasive species.

Keywords: diapause; flavivirus; insecticide resistance; mosquito genome; transposons.

Fig. 1.

Comparative analyses of the Ae. albopictus genome. (A) Phylogeny and divergence time estimation by molecular clock analysis. The mosquitoes An. gambiae, An. darlingi, Cx. quinquefasciatus, Ae. albopictus, and Ae. aegypti are estimated to have last shared a common ancestor with the fruit fly D. melanogaster ∼260 Mya. The anopheline and culicine branches are estimated to have diverged 217 Mya (SE = 180.8–256.9 Mya). Ae. albopictus and Ae. aegypti are estimated to have last shared a common ancestor 71.4 Mya (SE = 44.3–107.5 Mya). (B) Comparisons of repeat content among the six species. Families of repetitive elements are represented by colors: green, Gypsy; blue, Pao, light blue, Copia, red, RTE-BovB; orange, LOA; purple, R1; white, other. The horizontal extent of each bar represents the relative length of repeat within each family. Numbers to the right represent the total length of repeats in the respective genomes. (C) Copy number of TE insertions relative to the estimated time of insertion. Shown here are type I LINE (LINE/I) transposons. AEDALB (red), Ae. albopictus; AEDAEG (blue), Ae. aegypti. (D) Statistics of TE representation in the genomes of six species. 1, Length in base pairs; 2, percentage of genome represented. DNA, DNA transposon; SINE, short interspersed nuclear element.

Fig. 2.

Expansion and contraction of gene families among mosquito species. The numbers designate the number of gene families that have expanded (green) and contracted (red) since the split from the last common ancestor. The most recent common ancestor (MRCA) has 7,590 gene families. Aedae, Ae. aegypti; Aedal, Ae. albopictus; Anoda, An. darlingi; Anoga, An. gambiae; Cxqu, Cx. quinquefasciatus; Drome, D. melanogaster.

Fig. 3.

Proportion of OBP and OR gene transcripts in each expression level through development. The proportion of (A) OBP and (B) OR genes, containing nonexpressed genes, in each expressional level of each stage was calculated. The red, blue, and green columns refer to high (>1), medium (0.1–1) and low (<0.1) RPKM levels, respectively.