Brassica napus (AACC, oilseed rape) is an allotetraploid species derived from the putative progenitor diploid species B.rapa (AA) and B. oleracea (CC). To assess the influence of intensive breeding conditions on the evolution of the B. napus genome, Kovarik et al. employ cytogenetic and genomic approaches to analyze rDNA structure in 21 cultivars of B. napus.
The B. napus cultivars differ in degree and direction of rDNA homogenization; the prevalent direction of gene conversion (towards the A genome) correlates with the direction of expression dominance, indicating that gene activity may be required for interlocus gene conversion.
Sochorová, J., Coriton, O., Kuderová, A., Lunerová, J., Chèvre, A.-M., & Kovařík, A. (2016). Gene conversion events and variable degree of homogenization of rDNA loci in cultivars of Brassica napus. Annals of Botany, 119(1), 13–26. https://doi.org/10.1093/aob/mcw187