Molecular and Genetic Studies on Maize Transposable Elements-- Paramutation and Directed Transposition

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Novel interactions between the transposable elements of the Ac-Ds system in maize will be investigated. Preliminary studies indicate interaction or some form of information transfer between Ds elements and Ac-w derivatives on homologous chromosomes. The presence of the highly methylated wx-m9Ds-cy element on one chromosome leads to the paramutation-like inactivation and methylation of an Ac-w element at a distant position on the homologue. The Ds elements in wx-m6, wx-m9 and the State I Ds in standard position on chromosome II 9 do not inactivate but, in every heterozygote, cause Ac-w to move along its chromosome and be reinserted at the site occupied by the Ds element on the homologue. The small Ds I element in the wx-m1 allele does not act in trans and must be on the same chromosome to effect the migration of Ac-w. Molecular evidence indicates that Ac-w is reinserted in the wx-m1 gene. These interactions are limited to elements on homologous chromosomes. These studies will be extended and the interactions by genetic and molecular analyses wil be investigated. While much is known about transposable elements on the molecular level, this study is the first to suggest that directed transposition and site-specific insertion can and does occur. The continuation of this project will allow further information to be gathered on what could be a potential breakthrough on attempts to understand what, if any, function is performed by transposable elements in the normal, non-stressed genome of corn.