Mutator transposase is widespread in the grasses

Although the Mutntor. (Mu) system is well characterized in maize (Zea mays) , very little is known about this highly mutagenic system of transposons in ether grasses. Mutator is regulated by the MuDR class of elements, which e ncodes two genes, one of which, mudrA, has similarity to a number of bacter ial transposases. Experiments in our laboratory, as well as database search es, demonstrate that mudrA sequences are ubiquitous and diverse in the gras ses. In several species it is clear that multiple paralogous elements can b e present in a single genome. Tn some species such as wheat (Triticum aesti vum) and rice (Oryza sativa), mudrA-similar sequences are represented in cD NA databases, suggesting the presence of active Mtr transposon systems in t hese species. Further, in rice and ill. sorghum, mudrA-like genes are flank ed by long terminal inverted repeats, as well as the short host sequence di rect repeats diagnostic of insertion. Thus, there is ample evidence that sy stems related to Mu in maize are at least potentially active in a wide vari ety of grasses However, the mudrB gene, though important for Mu activity in maize, is not necessarily a component of Mu elements in other grasses.