Fig. 1

Processes and patterns of polyploidy in plants. Flowering plant genomes have an evolutionary history that includes multiple, lineage-specific, whole-genome doubling events. A model of a hypothetical allopolyploid genome derived from two progenitor diploid genomes (A and B) is shown in the figure. Hybridization and genome doubling set in motion short-term and long-term genomic processes, at the level of DNA sequence (top) and at the expression level (bottom). Young allopolyploids, which initially contain two genomes (A _T and B _T ) inherited from the parental genome donors, often display homoeologous recombination (‘gene conversion’), mutational loss and/or silencing of duplicated genes, intergenomic spread of TEs and differential rates of molecular evolution, as well as many different forms of biased or altered gene expression, including biased homoeolog expression and expression level dominance (not shown), and expression subfunctionalization (shown as partitioning of ancestral blue and green expression domains, bottom left) and neofunctionalization (novel red expression domain, bottom right)