Ikirara insertions reveal five new Anopheles gambiae transposable elementsin islands of repetitious sequence

Characterization of Anopheles gambiae genomic clones containing Ikirara inv erted repeats revealed five novel sequences related to known transposable e lements (TEs). One TE is related to the mariner/Tc1 superfamily of class II (DNA-to-DNA) transposons, while four are related to class I (RNA-mediated transposition) elements. Crusoe, the class II element, is most similar to t he Caenorhabditis elegans transposon Tc1-like TEs. Vash elements, represent ed twice in our clones, are related to the Q/T1 family of A. gambiae non-LT R retrotransposable elements. Guildenstern is a member of the RT1 and RT2 n on-LTR retrotransposon family. Although RT1 and RT2 elements normally have a highly stereotyped insertion preference for sequences within ribosomal ge nes, Guildenstern is not located in ribosomal sequence. JuanAg is the first anopheline member of the mosquito non-LTR retrotransposon family of Juan e lements that previously had included just the culicine elements JuanA and J uanC. Approximately 753 bp is missing from the central portion of the JuanA g reverse transcriptase gene, where an Ikirara inverted repeat is found in its stead. Ozymandias, the only LTR retrotransposon found in the clones, is most similar to the Drosophila melanogaster 412 element. Single Ikirara in verted repeats were also found adjacent to nontransposable element repetiti ous sequences. Our analysis suggests that the A. gambiae genome organizatio n could best be described as islands of short-period interspersion repetiti ous DNA in a sea of long-period interspersion, mostly unique sequence DNA.