THE INVETERATE WANDERER - STUDY OF ENHANCER WANDERING ON CHROMOSOME-3IN MAIZE

The transposition of the maize transposable element Enhancer (En) had been focused on one chromosome 3 for several generations. From the a1- m(Au) allele with an autonomous En, a new En reporter allele a1-m(r)39 27-1, was isolated that undergoes very infrequent and late excision ev ents, producing one or two small spots in the aleurone. This allele is seriously impaired in its capacity to excise. Coincident with the ori gin of this allele, an En was located at a site close to the a1 locus. From this initial insertion site, the movement of this En was followe d for three to four generations in 974 families with a higher transpos ition rate of this En (50% of the test-cross progeny) than that found in a previous study of En transposition. This is the first case report ed where a particular En was followed for more than three generations. The higher rate of wanderings of this En along the same chromosome le d to the term 'vagabond' En (En(vag)). Genetic evidence that En may tr anspose from a replicated donor site to an unreplicated site is provid ed. Speculative mechanisms on the origin of a1-m(r)3927-1 and En(vag)a re discussed.