THE PLANT CELL, Vol 5, Issue 5 515-522, Copyright © 1993 by American Society of Plant Biologists
Molecular Evidence That Chromosome Breakage by Ds Elements Is Caused by Aberrant Transposition
C. F. Weil and S. R. Wessler
Botany Department, University of Georgia, Athens, Georgia 30602
The transposable Dissociation (Ds) element of maize was first discovered as
a site of high-frequency chromosome breakage. Because both Ds-mediated
breakage and transposition require the presence of the Activator (Ac)
element, it has been suggested that chromosome breakage may be the outcome
of an aberrant transposition event. This idea is consistent with the
finding that only complex structures containing multiple Ds or Ac and Ds
elements have been correlated with chromosome breakage. In this report, we
describe two chromosome-breaking maize alleles that contain pairs of
closely linked but separate DS elements inserted at the Waxy locus. A
polymerase chain reaction assay was utilized to isolate intermediates in
the breakage process. The DNA sequence of these intermediates reveals
deletions and base pair changes consistent with transposon footprints that
may represent the junctions between fused sister chromatids. These results
provide direct molecular evidence that chromosome breakage is the result of
aberrant transposition events.
