MuTAnT: a family of Mutator-like transposable elements targeting TA microsatellites in Medicago truncatula

Transposable elements (TEs) are mobile DNA segments, abundant and dynamic in plant genomes. Because their mobility can be potentially deleterious to the host, a variety of mechanisms evolved limiting that negative impact, one of them being preference for a specific target insertion site. Here, we describe a family of Mutator-like DNA transposons in Medicago truncatula targeting TA microsatellites. We identified 218 copies of MuTAnTs and an element carrying a complete ORF encoding a mudrA-like transposase. Most insertion sites are flanked by a variable number of TA tandem repeats, indicating that MuTAnTs are specifically targeting TA microsatellites. Other TE families flanked by TA repeats (e.g. TAFT elements in maize) were described previously, however we identified the first putative autonomous element sharing that characteristics with a related group of short non-autonomous transposons.