title: Modulating crossover positioning by introducing large structural changes in chromosomes.
abstract: BACKGROUND
  Crossing over assures the correct segregation of the homologous chromosomes to both poles of the dividing meiocyte. This exchange of DNA creates new allelic combinations thus increasing the genetic variation present in offspring. Crossovers are not uniformly distributed along chromosomes; rather there are preferred locations where they may take place. The positioning of crossovers is known to be influenced by both exogenous and endogenous factors as well as structural features inherent to the chromosome itself. We have introduced large structural changes into Arabidopsis chromosomes and report their effects on crossover positioning.
  
  
  RESULTS
  The introduction of large deletions and putative inversions silenced recombination over the length of the structural change. In the majority of cases analyzed, the total recombination frequency over the chromosomes was unchanged. The loss of crossovers at the sites of structural change was compensated for by increases in recombination frequencies elsewhere on the chromosomes, mostly in single intervals of one to three megabases in size. Interestingly, two independent cases of induced structural changes in the same chromosomal interval were found on both chromosomes 1 and 2. In both cases, compensatory increases in recombination frequencies were of similar strength and took place in the same chromosome region. In contrast, deletions in chromosome arms carrying the nucleolar organizing region did not change recombination frequencies in the remainder of those chromosomes.
  
  
  CONCLUSIONS
  When taken together, these observations show that changes in the physical structure of the chromosome can have large effects on the positioning of COs within that chromosome. Moreover, different reactions to induced structural changes are observed between and within chromosomes. However, the similarity in reaction observed when looking at chromosomes carrying similar changes suggests a direct causal relation between induced change and observed reaction.
authors: Department of Molecular Plant Physiology, Radboud University Nijmegen, Institute for Water and Wetland Research (IWWR), Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands. a.ederveen@science.ru.nl.
authors: Antoine
authors: A
authors: Ederveen
authors: Netherlands Bioinformatics Centre, 260 NBIC, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. yuching.lai@gmail.com.|The Delft Bioinformatics Lab, Department of Intelligent Systems, Delft University of Technology, Mekelweg 4, 2628 CD, Delft, The Netherlands. yuching.lai@gmail.com.
authors: Yuching
authors: Y
authors: Lai
authors: Netherlands Bioinformatics Centre, 260 NBIC, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. marc.van.driel@philips.com.|Current affiliation: Philips Research, High Tech Campus 11, 5656 AE, Eindhoven, The Netherlands. marc.van.driel@philips.com.
authors: Marc A
authors: MA
authors: van Driel
authors: Department of Molecular Plant Physiology, Radboud University Nijmegen, Institute for Water and Wetland Research (IWWR), Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands. t.gerats@science.ru.nl.
authors: Tom
authors: T
authors: Gerats
authors: Department of Molecular Plant Physiology, Radboud University Nijmegen, Institute for Water and Wetland Research (IWWR), Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands. jl.peters@science.ru.nl.
authors: Janny L
authors: JL
authors: Peters
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D002872:Chromosome Deletion; D007446:Chromosome Inversion / Q000528:radiation effects; D032461:Chromosomes, Plant / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D003434:Crossing Over, Genetic / Q000235:genetics*; D005720:Gamma Rays; D005787:Gene Frequency; D005838:Genotype; D019656:Loss of Heterozygosity / Q000528:radiation effects; D008540:Meiosis; D011995:Recombination, Genetic