Molecular and Genetic Studies on Maize Elements

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The functioning of the Ac transposable element in maize is controlled by its own product, transposase, that acts as a transactivating protein resulting in a steady state condition. Activation of Ac is associated with the demethylation of the promoter region. Structurally altered, defective Ac elements that differ in the demethylation of their promoter by transposase will be employed in a study designed to determine the molecular basis for the promoter demethylation. The second part of this project involves an analysis of the long range cis interaction between elements of the Ac-Ds system. When an Ac and a Ds element are coupled on the same chromosome arms, the distal element becomes methylated and is not digested by methylase-sensitive restriction enzymes. This effect is limited to elements coupled on the same chromosome arm, but they may be as far apart as 50 map units. Many different double and triple combinations of Ac, Ds and other marker genes will be constructed to study the nature of this long range cis interaction. During a period of previous NSF support, the author of this proposal has discovered that one gene can influence the behavior of another gene on the same, chromosome over much greater distances than previously imagined. He now proposes to pursue this discovery, and attempt to elucidate the mechanism by which such long-range interactions among genes occur.