Regulation of Mu Activity in Maize

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9603119 Freeling Technical section A typical Mutator (Mu) line of maize carries about 100 Mu transposons and about five autonomous Mu transposons called MuDR. A minimal line that carries a single MuDR has been characterized. All phenotypes induced by transposition, excision, demethylation, and suppression of Mu-induced alleles, are specified by this element. Deletion analysis of MuDR-1 will be continued in order to ascribe specific functions to regions of MuDR DNA structure and domains of the encoded proteins A and B. Antibody to A will be prepared and with the already available antibody to B, immunolocalization and nuclear protein coprecipitation experiments will be done. The mechanism of Mu suppression will be studied using a quantitative assay, and reverse genetics will be used to target small deletions to particular regions of MuDR-1 (p1). The observed phenomenon whereby Mu becomes less active during development and following inbreeding even though intact MuDR elements exist in the genome called "dominant negative regulation", will be investigated. Promoter diversity will be studied using a Mu excision event which resulted in a series of mis-repair events affecting a region of about 400 bp. A single MuDR element has been introduced into oat via a sexual cross and its behavior in a non-native species of grass will be analyzed. Non-technical abstract A transposable element native to corn, Mu, will be studied. A strain which contains only one master element, in contrast to the many usually present in the corn genome, will be used to study the structure and the function of the element. A phenomenon, dominant negative regulation, which results in a cession of activity by the Mu element during development and following inbreeding even though many structurally intact elements are present in the genome, will be investigated. The availability of this strain and its progeny also makes it possible to study the effects of variation in promoter sequence and the behavior of the transposon when it is transferred to a foreign host.