From Alpha-Duplication to Triplication and Sextuplication

Abstract

The Brassica napus is a truly great genome for the study of genome and gene family evolution, with a rich history of past whole-genome duplication (WGD) events. The genome has undergone a total of 5 rounds of duplications since the common ancestor with the basal angiosperm Amborella. This level of genetic redundancy is unparalleled by any other flowering plant genome that was sequenced prior to the release of the B. napus genome assembly. Three recent WGDs that occurred within the lineage of Brassicaceae are of significant value to polyploid research, namely the ‘alpha’ duplication event, the Brassica triplication and B. napus allotetraploidization. These events occurred at different evolutionary times and are representatives of paleo-polyploidy, meso-polyploidy, and neo-polyploidy, respectively. Studies of evolutionary changes and transcriptional regulation of duplicate genes derived from these WGD events have led to groundbreaking discoveries in the dynamics of polyploid genomes, including genome reorganization, gene fractionation (loss of duplicated genes), and genome dominance. These breakthroughs were largely facilitated by a number of innovations in computational methods, databases, and interconnected cyberinfrastructure that are devoted to plant comparative genomics research. With its genome now fully deciphered, B. napus continues to be one of the most important model organisms in post-polyploidy genome evolution research.