Molecular genetics of the Mu transposons of maize

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The Robertson's Mutator (Mu) transposable element system is a highly active transposon system in maize that generates new mutations at frequencies of 50-fold over background. The Mu system has several unusual properties that distinguish it from other eukaryotic transposable element systems, and there is little known regarding the mechanism of transposition of the Mu elements. The proposed studies are aimed towards a better understanding of this transposon system at the molecular level. We will characterize previously generated genetic material which show altered transposition properties as follows. We plan to clone and characterize a derivative Mu element that heritable exhibits a 10 to 100 fold increase in excision frequency relative to the progenitor Mu1 element. This element can be used to answer specific questions about Mu transposition, as well as providing a sensitive marker for excision activity. We will also analyze a Mu lineage in which the transposon system was inactivated by continued selfing, in order to understand the basis of dose-dependent regulation of Mu transposon activity. In addition to the above studies, we will develop assays for Mu transposition in transgenic dicotyledenous plants. The assays will be used to determine the sequence requirements for transposition, and the function of specific sequences within the Mu termini that we have previously identified as likely to play an important role in transposition. %%% Due to the unusual properties of Mu transposons, these studies should add to our knowledge of mechanisms of transposition and DNA re-arrangements.