Originally published as Genetics Published Articles Ahead of Print on July 18, 2006.

Genetics, Vol. 174, 145-154, September 2006, Copyright © 2006
doi:10.1534/genetics.105.048322

The Maize Ab10 Meiotic Drive System Maps to Supernumerary Sequences in a Large Complex Haplotype

Rebecca J. Mroczek*,{dagger}, Juliana R. Melo*, Amy C. Luce*, Evelyn N. Hiatt{ddagger},§ and R. Kelly Dawe*,{ddagger},1

* Department of Plant Biology and {ddagger} Department of Genetics, University of Georgia, Athens, Georgia 30602, {dagger} Department of Biology, University of Arkansas, Fort Smith, Arkansas 72913 and § Department of Biology, Kentucky Wesleyan College, Owensboro, Kentucky 42301

1 Corresponding author: Department of Plant Biology, Miller Plant Sciences Bldg., University of Georgia, Athens, GA 30602.
E-mail: kelly{at}plantbio.uga.edu

The meiotic drive system on maize abnormal chromosome 10 (Ab10) is contained within a terminal domain of chromatin that extends the long arm of Ab10 to ~1.3 times the size of normal chromosome 10L. Ab10 type I (Ab10-I) does not recombine with normal chromosome 10 (N10) over an ~32-cM terminal region of the long arm. Comparative RFLP mapping demonstrates that multiple independent rearrangements are responsible for the current organization of Ab10-I, including a set of nested inversions and at least one long supernumerary segment at the end of the chromosome. Four major meiotic drive functions, i.e., the recombination effect, smd3, 180-bp neocentromere activity, and the distal tip function, all map to the distal supernumerary segment. TR-1-mediated neocentromere activity (the fifth known drive function) is nonessential in the type II variant of Ab10 and maps to a central region that may include a second supernumerary insertion. Both neocentromere activity and the recombination effect behave as dominant gain-of-function mutations, consistent with the view that meiotic drive involves new or alien gene products. These and other data suggest that the Ab10 meiotic drive system was initially acquired from a related species and that a complex haplotype evolved around it.