Fractionation mutagenesis and similar consequences of mechanisms removing dispensable or less-expressed DNA in plants.

Unlike in mammals, plants rapidly delete functionless, nonrepetitive DNA from their genomes. Following paleopolyploidies, duplicate genes are deleted by intrachromosomal recombination. This may explain how flowering plants have survived multiple whole genome duplications. Genes are disproportionately lost from one parental subgenome, the subgenome that is less expressed in the polyploid. The origin of this unbalanced expression between genomes remains unknown. The consequences of the tradeoffs between transposon repression and gene expression represent one potential explanation of genome dominance. If so, the same mechanisms may act in heterosis: genome dominance is like inbreeding depression. Regulatory DNA deletion following polyploidy combined with abundant RNA-seq expression datasets are being used to generate testable hypothesizes regarding the function of specific cis-regulatory sequences.