Genome Evolution During Polyploid Formation Within Cereals

Polyploid formation or genome duplication has been well documented to be a major mode of speciation in higher plants. Most successful allopolyploids have the ability to invoke and maintain diploid-like behavior.  Recent studies on natural and synthetic polyploid species have revealed non-Mendelian behavior in polyploid formation, but others have not. In addition, some species demonstrated rapid genome changes following polyploid formation, while others still maintain their conserved progenitor genomes. Some species display non-random genome changes, whereas others show mostly random changes. Some species have genomic changes that occur in the F1 hybrid between the different progenitors, while other changes appear to be the direct result of genome doubling.  All of the above observations provide some insights into polyploid stabilization and subsequent evolution, and it is obvious that both genetic and epigenetic factors are involved. The overall genetic and epigenetic variations appear to be often associated with repetitive sequences and transposon elements. It is becoming clear that genomic sequence elimination and chromosome rearrangement are probably the major forces guiding cytological diploidization. Gene non-functionalization, sub-functionalization, neo-functionalization, as well as other epigenetic modifications, are likely the leading factors promoting genetic diploidization.