Phylogenetic analysis reveals Stowaway-like elements may represent a fourth family of the IS630-Tc1-mariner superfamily

The genomes of plants, like virtually all other eukaryotic organisms, harbor a diverse array of mobile elements, or transposons. In terms of numbers, the predominant type of transposons in many plants is the miniature inverted-repeat transposable element (MITE). There are three archetypal MITEs, known as Tourist, Stowaway, and Emigrant, each of which can be defined by a specific terminal inverted-repeat (TIR) sequence signature. Although their presence was known for over a decade, only recently have open reading frames (ORFs) been identified that correspond to putative transposases for each of the archetypes. We have identified two Stowaway elements that encode a putative transposase and are similar to members of the previously characterized IS630-Tc1-mariner superfamily. In this report, we provide a high-resolution phylogenetic analysis of the evolutionary relationship between Stowaway, Emigrant, and members of the IS630-Tc1-mariner superfamily. We show that although Emigrant is closely related to the pogo-like family of elements, Stowaway may represent a novel family. Integration of our results with previously published data leads to the conclusion that the three main types of MITEs have different evolutionary histories despite similarity in structure.