THE PLANT CELL, Vol 8, Issue 5 823-830, Copyright © 1996 by American Society of Plant Biologists
Localization of T-DNA Insertions in Petunia by Fluorescence in Situ Hybridization: Physical Evidence for Suppression of Recombination
R. ten Hoopen, T. P. Robbins, P. F. Fransz, B. M. Montijn, O. Oud, AGM. Gerats and N. Nanninga
Institute for Molecular Cell Biology, BioCentrum Amsterdam, University of Amsterdam, Kruislaan 316, 1098 SM Amsterdam, The Netherlands
Using fluorescence in situ hybridization (FISH) with metaphase
preparations, we localized a 4-kb single-copy T-DNA sequence in a group of
petunia transformants. The selected T-DNAs previously had been shown to be
linked to the phenotypic marker FI on chromosome II. Linkage analysis had
revealed that recombination around the FI locus is suppressed in a wide
cross relative to an inbred recombination assay. The localization of six
FI-linked T-DNAs and the FI locus itself, using FISH, revealed a number of
aspects of recombination in petunia: (1) the central region of chromosome
II showed at least a 10-fold suppression of recombination in wide crosses
relative to the distal region; (2) recombination in wide hybrids over
two-thirds of the chromosome was extremely low; and (3) recombination
between completely homologous chromosomes in an inbred cross also was
suppressed in the central region. In addition, the T-DNAs were not evenly
distributed along the chromosome, suggesting a possible preference for a
distal position for T-DNA integration. Implications for such a preference
are discussed.
