USE OF AC AS AN INSERTIONAL MUTAGEN IN ARABIDOPSIS

A pilot-scale transposon mutagenesis experiment using a modified auton omous Activator (Ac) element, Ac Delta Nael, was carried out in Arabid opsis thaliana. Four different transformants carrying Ac elements in d ifferent and defined genomic locations were used to generate 1000 plan ts carrying approximately 500 independent germinal transposition event s. These plants were then selfed and the 1000 families screened in tis sue culture and soil for phenotypic mutants. Fifty different families segregated mutations in their progeny. Preliminary Southern blot analy sis of 29 families which segregated mutant progeny, showed that 28 had a transposed Ac. Six of the families were further tested for linkage between the transposed Ac and the mutant phenotype, and instability of the putatively tagged locus. Two of the mutants were shown to be tagg ed as they were tightly linked to a transposed Ac, and somatic and ger minal reversion was associated with loss of Ac. One other mutant locus was shown to be closely linked to a transposed Ac, and therefore was likely to be tagged. The remaining three mutations were not tagged as they were not linked to a transposed Ac. In two of the tagged mutants Ac had transposed to closely linked sites, while in a third mutant the co-segregating Ac had transposed to a site which was not tightly link ed to the donor T-DNA. Multiple insertions into the DIF1 locus were fo und, due to the preferential transposition of Ac to a linked site.