Systematic screening of Anopheles mosquito genomes yields evidence for a major clade of Pao-like retrotransposons

We developed a degenerate PCR procedure to simultaneously amplify products from divergent retrotransposon families within the genomes of Anopheles mos quitoes. The procedure required cloning of multiple PCR products, but more than half of the clones subsequently sequenced were of retrotransposon orig in. These included Copia-like and LINE retrotransposons, as well as the fir st Gypsy-like retrotransposons reported from mosquitoes. Furthermore, some Anopheles retrotransposon sequences showed similarity to the divergent Pao element from the silkmoth Bombyx mori. Phylogenetic analyses provided consi stently strong bootstrap support (> 95%) for a major clade of Pao-like retr otransposons, which includes five mosquito sequences and the recently disco vered Drosophila retrotransposons BEL and ninja. This appears to represent a new family of Pao-like LTR-retrotransposons distinct from the Copia and G ypsy families.