Sequence Elimination and the Genomic Evolution of Allopolyploid Plants

Allopolyploids,resulted from combination of two or more differentiated genomes,have undergone DNA sequence elimination in the early stage after the formation of allopolyploids.The sequences eliminated,involving not only high-copy but also low-copy DNA sequences,mostly are from one of the parental genomes.The modes of sequence elimination are different among both various genomic constituents and species,perhaps affected by the cytoplasm.Although the mechanisms of molecular interactions that underlie sequence elimination are not very clear at present,many investigations have indicated that inter-homoeologous chromosomal recombination is not the main impact factor.It has been speculating that sequence elimination has increased the divergence between homoeologous chromosomes,provided a physical basis for rapid restoration of diploid-like chromosome paring pattern in meiosis following polyploidization,and thereby possibly demonstrated polyploidy-facilitated adaptation.