Homeologous recombination plays a major role in chromosome rearrangements that occur during meiosis of Brassica napus haploids

Chromosomal rearrangements have played a major role in the evolution and speciation of plants and animals and can be triggered by recombination between distinct but related regions. Brassica napus (AACC; 2n=38) is a recent allopolyploid species resulting from multiple independent hybridization events between ancestors of the modern diploid B. oleracea (CC) and B. rapa (AA), whose genomes are widely replicated. In this paper, we use molecular markers spanning 4 linkage groups to genotype progenies of haploid B. napus (AC, n=19) and analyze the extent to which chromosomal rearrangements originate from homeologous exchanges during meiosis. We show that duplications and losses of chromosomal regions frequently occur during meiosis of B. napus haploids and provide genetic evidence that at least 51 to 65% of them are due to recombination between regions of primary homeology. This represents a 10 to 100 fold increase compared to the frequency of homeologous recombination measured in euploid lines. We also observed that an average of 0.7 and 0.8 autosyndetic bivalents form at Metaphase I within C or A chromosomes, respectively, which indicates that recombination might also occur between regions showing intragenomic homology (paralogues). These results are discussed in the context of genome evolution of B. napus.

Key Words: Brassica napus, genome rearrangements, homeologous recombination, meiosis, polyploidy

This article has been cited by other articles:

				R. T. Gaeta, J. C. Pires, F. Iniguez-Luy, E. Leon, and T. C. Osborn Genomic Changes in Resynthesized Brassica napus and Their Effect on Gene Expression and Phenotype PLANT CELL, November 1, 2007; 19(11): 3403 - 3417. [Abstract] [Full Text] [PDF]

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