Mutator and MULE transposons

Abstract

Because it is highly mutagenic and relatively non-specific, the Mutator system of transposons has proved to be an extraordinarily useful tool for maize geneticists. It has also proved to be a valuable model system for understanding the basic biology of transposons in higher eukaryotes, particularly the means by which transposons are epigenetically silenced by their hosts. Further, the wide distribution and remarkable variety of Mu-like elements (MULEs) among plant species has illuminated the role that transposons can play in the evolution of genomes. This chapter will provide an overview of the biology and evolution of this highly active and diverse family of transposable elements.

Mutator and MULE Transposons

“…All Mutator transposons share similar, ∼215 bp terminal inverted repeats (TIRs), but each class of these transposons contains distinct internal sequences (7,8). MuDR elements are the autonomous class of the Mutator element (9,10,11).…”

“…1A). Interestingly, while genes homologous to mudrA are extremely widespread and apparently ancient, those homologous to mudrB are restricted to the genus Zea (8,12). Transcription of these two genes is convergent and is initiated from within the nearly identical TIRs (TIRA and TIRB, respectively) (Fig.…”

“…2). As the captured sequences are very similar to the cognate host genes, it is likely that these sequences were captured, or transduplicated, relatively recently (8). (39,40).…”

“…Deletions within MuDR elements are consistent with strand slippage during template mediated repair, which results in a deleted region flanked by short repeats (24). While deletion events often occur late in the germinal lineage, they can also occur in earlier during development, resulting in clonal sectors of various sizes in which only a deletion derivative of a full length element is present (8,49). In combination with evidence for clonal sectors in which elements have duplicated early during development, this observation suggests that excisions are happening prior to the last few cell divisions, but that those excisions are repaired successfully, resulting in duplication events, or unsuccessfully, resulting in deletion derivatives (9).…”

Transposition of a Rice Mutator-Like Element in the Yeast Saccharomyces cerevisiae

“…The founder elements include the autonomous element MuDR and the nonautonomous elements (Mu1 to Mu8 and Mu10 to Mu13); MuDR generates the transposition machinery for the movement of all these elements (Bennetzen et al, 1984;Freeling, 1984;Chen et al, 1987;Talbert et al, 1989;Fleenor et al, 1990;Chomet et al, 1991;Hershberger et al, 1991;Qin et al, 1991;Lisch et al, 1995;Dietrich et al, 2002;Lisch and Jiang, 2009;Tan et al, 2011). All Mu elements share high sequence similarity in their terminal inverted repeats (TIRs; ;220 bp) while containing heterogeneous internal sequences.…”