Different Strategies to Persist: The pogo-Like Lemi1 Transposon Produces Miniature Inverted-Repeat Transposable Elements or Typical Defective Elements in Different Plant Genomes

摘要

Miniature inverted-repeat transposable elements (MITEs) are a particular type of defective class II elements present in genomes as high-copy-number populations of small and highly homogeneous elements. While virtually all class II transposon families contain non-autonomous defective transposon copies, only a subset of them have a related MITE family. At present it is not known in which circumstances MITEs are generated instead of typical class II defective transposons. The ability to produce MITEs could be an exclusive characteristic of particular transposases, could be related to a particular structure of certain defective class II elements, or could be the consequence of particular constraints imposed by certain host genomes on transposon populations. We describe here a new family of pogo -like transposons from Medicago truncatula closely related to the Arabidopsis Lemi 1 element that we have named MtLemi 1. In contrast to the Arabidopsis Lemi 1, present as a single-copy element and associated with hundreds of related Emigrant MITEs, MtLemi 1 has attained 30 copies and has not generated MITEs. This shows that a particular transposon can adopt completely different strategies to colonize genomes. The comparison of AtLemi 1 and MtLemi 1 reveals transposase-specific domains and possible regulatory sequences that could be linked to the ability to produce MITEs.