Molecular analysis of ds controlling element mutations at the adh1 locus of maize.

An active maize Adhl-F gene, a Ds-induced mutant of this gene, and two independent Ac-induced revertant alleles have been isolated. The Ds mutant differs from the progenitor allele in having a 405-base pair insertion flanked by a direct repeat of 8 bp. The repeat is a duplication of the 8 bp existing at the point of insertion in the 5' untranslated region of the gene. The insertion sequence is AT-rich (A, adenine; T, thymine) and has 11-bp inverted repeat sequences at its termini. In the revertants the insertion with its inverted repeats is deleted, but the 8-bp direct repeats remain in modified form. These results establish that the 405-bp sequence is a Ds element. The Adh1 messenger RNA level is low in the Ds mutant, and it appears that new sites for transcription initiation or RNA processing or both are used. There are at least 30 sequences in the maize genome related to the Ds element.