Originally published as Genetics Published Articles Ahead of Print on November 1, 2004.

Genetics, Vol. 169, 981-995, February 2005, Copyright © 2005
doi:10.1534/genetics.104.033738

Distribution of Activator (Ac) Throughout the Maize Genome for Use in Regional Mutagenesis

Judith M. Kolkman*,1, Liza J. Conrad*,{dagger},1, Phyllis R. Farmer*, Kristine Hardeman{ddagger}, Kevin R. Ahern*, Paul E. Lewis*, Ruairidh J. H. Sawers*, Sara Lebejko{ddagger}, Paul Chomet{ddagger} and Thomas P. Brutnell*,2

* Boyce Thompson Institute, Cornell University, Ithaca, New York 14853
{dagger} Department of Plant Breeding, Cornell University, Ithaca, New York 14853
{ddagger} Monsanto/Mystic Research, Mystic, Connecticut 06355

2 Corresponding author: Boyce Thompson Institute, Cornell University, 1 Tower Rd., Ithaca, NY 14853.
E-mail: tpb8{at}cornell.edu

A collection of Activator (Ac)-containing, near-isogenic W22 inbred lines has been generated for use in regional mutagenesis experiments. Each line is homozygous for a single, precisely positioned Ac element and the Ds reporter, r1-sc:m3. Through classical and molecular genetic techniques, 158 transposed Ac elements (tr-Acs) were distributed throughout the maize genome and 41 were precisely placed on the linkage map utilizing multiple recombinant inbred populations. Several PCR techniques were utilized to amplify DNA fragments flanking tr-Ac insertions up to 8 kb in length. Sequencing and database searches of flanking DNA revealed that the majority of insertions are in hypomethylated, low- or single-copy sequences, indicating an insertion site preference for genic sequences in the genome. However, a number of Ac transposition events were to highly repetitive sequences in the genome. We present evidence that suggests Ac expression is regulated by genomic context resulting in subtle variations in Ac-mediated excision patterns. These tr-Ac lines can be utilized to isolate genes with unknown function, to conduct fine-scale genetic mapping experiments, and to generate novel allelic diversity in applied breeding programs.




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