Homeologous recombination plays a major role in chromosome rearrangements that occur during meiosis of Brassica napus haploids.
Chromosomal rearrangements can be triggered by recombination between distinct but related regions. Brassica napus (AACC; 2n = 38) is a recent allopolyploid species whose progenitor genomes are widely replicated. In this article, we analyze the extent to which chromosomal rearrangements originate from homeologous recombination during meiosis of haploid B. napus (n = 19) by genotyping progenies of haploid x euploid B. napus with molecular markers. Our study focuses on three pairs of homeologous regions selected for their differing levels of divergence (N1/N11, N3/N13, and N9/N18). We show that a high number of chromosomal rearrangements occur during meiosis of B. napus haploid and are transmitted by first division restitution (FDR)-like unreduced gametes to their progeny; half of the progeny of Darmor-bzh haploids display duplications and/or losses in the chromosomal regions being studied. We demonstrate that half of these rearrangements are due to recombination between regions of primary homeology, which represents a 10- to 100-fold increase compared to the frequency of homeologous recombination measured in euploid lines. Some of the other rearrangements certainly result from recombination between paralogous regions because we observed an average of one to two autosyndetic A-A and/or C-C bivalents at metaphase I of the B. napus haploid. These results are discussed in the context of genome evolution of B. napus.
Nicolas
Stéphane D
SD
UMR INRA-Agrocampus Rennes, Amélioration des Plantes et Biotechnologies Végétales, 35653 Le Rheu, France.
Le Mignon
Guillaume
G
Eber
Frédérique
F
Coriton
Olivier
O
Monod
Hervé
H
Clouet
Vanessa
V
Huteau
Virginie
V
Lostanlen
Antoine
A
Delourme
Régine
R
Chalhoub
Boulos
B
Ryder
Carol D
CD
Chèvre
Anne Marie
AM
Jenczewski
Eric
E
D000483:Alleles; D029688:Brassica napus / Q000166:cytology* / Q000235:genetics*; D020090:Chromosome Segregation; D032461:Chromosomes, Plant / Q000235:genetics*; D003433:Crosses, Genetic; D018628:Gene Dosage; D015321:Gene Rearrangement; D005819:Genetic Markers; D018745:Genome, Plant / Q000235:genetics; D006238:Haploidy; D017404:In Situ Hybridization, Fluorescence; D008540:Meiosis / Q000235:genetics*; D008677:Metaphase; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000235:genetics*
D005819:Genetic Markers