Retrotransposon “Qian” mediated segmental duplication in silkworm, Bombyx mori

Abstract Transposable elements constitute a large fraction of the eukaryotic genomes. They have the potential to alter genome structure and play a major role in genome evolution. Here, we report a segmental duplication mediated by a novel long terminal repeat (LTR) retrotransposon as the cause of an egg-shell recessive lethal mutant ( l-e m mutant) in silkworm ( Bombyx mori ). The segmental duplication resulted in the duplication of six genes and the disruption of two genes. Disruption of BmEP80 ( B. mori egg protein 80 ), a gene encoding a major egg-shell structure protein, is likely responsible for the lethal water-loss phenotype in the l-e m / l-e m mutant. Our data revealed that BmEP80 is present in the inner egg-shell layer and plays important roles in resistance to water efflux form eggs. A novel LTR retrotransposon (named as “ Qian ”) was identified and the model for the Qian -mediated chromosomal segmental duplication was proposed. Detail biochemical and genomic analyses on the l-e m mutant offer an opportunity to demonstrate that an LTR retrotransposon could trigger duplication of a chromosomal segment (∼96.3 kb) and confer novel phenotype.