Cloning of the bronze locus in maize by a simple and generalizable procedure using the transposable controlling element Activator (Ac)

The bronze (bz) locus of maize has been cloned by an indirect procedure utilizing the cloned transposable controlling element Activator (Ac). Restriction endonuclease fragments of maize DNA were cloned in bacteriophage λ and recombinant phage with homology to the center of the Ac element were isolated. The cloned fragments were analyzed to determine which contained sequences that were structurally identical to a previously isolated Ac element. Two such fragments were identified. Sequences flanking the Ac element were subcloned and used to probe genomic DNA from plants with well-defined mutations at the bz locus. By this means, it was established that one of the genomic clones contained a bz locus sequence. The subcloned probe fragment was then used to clone a nonmutant Bz allele of the locus. The method described here should prove useful in cloning other loci with Ac insertion mutations.