A physical map for an Asian malaria mosquito, Anopheles stephensi

Abstract

Physical mapping is a useful approach for studying genome organization and evolution as well as for genome sequence assembly. The availability of polytene chromosomes in malaria mosquitoes provides a unique opportunity to develop high-resolution physical maps. We report a 0.6-Mb-resolution physical map consisting of 422 DNA markers hybridized to 379 chromosomal sites of the Anopheles stephensi polytene chromosomes. This makes An. stephensi second only to Anopheles gambiae in density of a physical map among malaria mosquitoes. Three hundred sixty-three (363) probes hybridized to single chromosomal sites, whereas 59 clones yielded multiple signals. This physical map provided a suitable basis for comparative genomics, which was used for determining inversion breakpoints, duplications, and origin of novel genes across species.

Figure 1.

A physical map showing the locations of 345 markers on five chromosome arms of Anopheles stephensi. (') indicates multiple located clones with signals of equal intensity. (*) indicates primary hybridization sites of multiply located clones. Positions of breakpoints for polymorphic inversion are shown with lower case letters.

Figure 2.

Fluorescent in situ hybridization of Anopheles stephensi cDNA and BAC clones labeled with Cy3 (red) and Cy5 (blue) to polytene chromosomes from ovarian nurse cells. (A) Hybridization of An. stephensi-specific cDNA to the heterochromatin of the X chromosome. (B) Mapping of the An. stephensi cDNA to a region outside of the common polymorphic inversion 2Rb. (C) Hybridization of two An. stephensi BAC clones with euchromatic regions on the 3R chromosomal arm. Arrows indicate signals of hybridization.