THE MAIZE TRANSPOSABLE ELEMENT SYSTEM AC DS AS A MUTAGEN IN ARABIDOPSIS - IDENTIFICATION OF AN ALBINO MUTATION INDUCED BY DS INSERTION

A two-component transposon system based on the Ac element of maize was used as a mutagen in Arabidopsis thaliana. Transposition of a Ds elem ent marked with a hygromycin-resistance gene was activated from four d ifferent locations in the Arabidopsis genome. The progeny of 201 plant s carrying independent transposition events were screened for mutants with severe, visible phenotypes. Seven mutants were identified and fou r of them were analyzed genetically. Three mutations were shown to be very closely linked to a transposed copy of the element. Moreover, a m utation (alb3) causing an albino phenotype was conclusively shown to b e caused by insertion of the Ds element: somatic and germinal reversio n of the mutation occurred in the presence of the transposase gene but not in its absence, and in three revertants the Ds had excised from i ts position in the mutant line. The DNA adjacent to Ds in the mutant w as isolated and it was demonstrated that revertants retained part of t he 8-bp duplication caused by insertion of Ds. These experiments indic ate that the Ac/Ds system can be used as an insertional mutagen in the heterologous host Arabidopsis, which will permit the isolation of gen es from this species by transposon tagging.