Similar to what was observed for arabidopsis, the authors clearly demonstrate that biased fractionation has occurred in the maize genome following the most recent tetraploidization event. This preferential removal of genes from one of the ancestral diploid genomes was revealed through comparison to Sorghum, which shared a common ancestor with maize directly prior to the tetraploidization event. It is shown that the missing genes were actually lost, rather than translocated, and that the gene losses have largely occurred via many small events, rather than in blocks. Illegitimate recombination is suspected as a mechanism for initial disruption and removal events, evidenced by presence of direct repeats in carefully studied examples of disruptions. Careful investigations of how else the remnant ancestral diploid genomes might be distinguished were performed, finding that both recombination and nucleotide substitution rates were similar. Also, a preliminary investigation of methylation levels failed to show a clear correlation. Although there are as yet no smoking guns, an epigenetic mechanism for distinguishing between the two diploid genomes newly present in the tetraploid is proposed to explain the source of the bias. Nick Lauter, 2010
Woodhouse MRH, Schnable J, Pedersen B, Lyons E, Lisch D, Subramaniam S, Freeling M (2010) Following Tetraploidy in Maize, a Short Deletion Mechanism Removed Genes Preferentially from One of the Two Homeologs. PLoS Biol 8:doi:10.1371/journal.pbio.1000409
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