Ancient and recent polyploidy in monocots

Abstract

At least two whole-genome duplications (WGD) have profoundly influenced the evolution of most, if not all, grass (Poaceae) genomes, with the most recent of these predating the divergence of these lineages by 20 million or more years. Taxa within each major lineage of Poaceae (e.g., Panicoideae, Ehrhartoideae, Pooideae) have independently experienced additional polyploidizations that have been of central importance to the evolution and productivity of some of our most important crop plants [for example, sugarcane (Saccharum spp.), and durum and bread wheat (Triticum spp.)]. Following polyploidy, adaptation to the duplicated state is evident at the levels of transmission genetics, chromosome structure, and gene repertoire. While most duplicated chromosomal regions re-establish largely independent evolution within a few million years, 70-million-year-old duplicated chromosome segments in one unusual region of the rice genome and its orthologs in other grasses have continued to exhibit concerted evolution more recently than the divergence of rice subspecies japonica and indica an estimated 400,000 years ago.