The transposable element, Mu, found in maize is unique in several ways. The element was first cloned by this laboratory, but subsequent studies by several laboratories demonstrated that all of the cloned elements identified as Mu were imperfect in that they could not in themselves induce transposition. The "master" element was finally cloned and characterized by this laboratory, as well as two other laboratories in 1991, and the proposed work is a continuation of those studies. The element encodes two messages when in an active chromosomal position. Differences in chromosomal position and mode of sexual transmission can effect the rate of MuR1 transposition. We have also shown that the element can and will automutate, and we will use these automutants along with other more conventionally derived mutants to describe the mechanism of transposition and functions of the two transcripts and their proteins. A long term goal will be to attempt to utilize this element to transposon tag cereal crops that are so important to world nutrition. %%% Transposons, or "jumping genes" have proven to be of intellectual interest in understanding fundamental genetic mechanisms and of practical importance, in that they can be engineered as gene vectors. Both of those interests are best served in the complete characterization and understanding of the characteristics of such DNA sequences. Mu is extremely important to characterize in that it has already been found to have properties which are unique among the hundreds of transposable elements so far characterized. The detection of the fragments of the element in barley offers the long-range hope that genetic engineering might provide an extremely important tool for improving cereal crops throughout the world.
