Chromosomal and gene expression changes in Brassica Allopolyploids
Résumé
Brassica species have a long common history with polyploidy, and in the last two decades their study has contributed to renewed interest in plant polyploidy research. During this time they have served as fruitful models with which to further our understanding of questions relating to innovation, adaptation, and the evolutionary success of polyploids. Brassica species have undergone recurrent rounds of polyploidy, and therefore provide ways to analyze the consequences of polyploidy over different timescales. Studies on resynthesized Brassica allotetraploids (specifically on synthetic oilseed rape, B. napus) have highlighted the high structural plasticity of the newly formed allopolyploid genome as well as highlighting numerous expression changes, both of which drive rapid generation of phenotypic variation. Increasingly accumulating evidence has revealed the broad diversity of the mechanisms and levels of regulation (genetically or epigenetically controlled) at the origins of the high dynamics of the newly formed Brassica polyploid genome. In the very near future, the availability of the complete genome sequence of the natural B. napus together with genome sequences of its two diploid progenitors B. rapa and B. oleracea will certainly enable further understanding of the many mechanisms that have contributed to the evolution of the Brassica genome.