|Ma, Xue-Feng - AGRONOMY-UNIV OF MISSOURI|
Submitted to: Cytogenetics and Genome Research
Publication Type: Review Article
Publication Acceptance Date: March 11, 2004
Publication Date: N/A
Technical Abstract: Polyploidy is a prominent mode of speciation in higher plants. Because of the coexistence of closely related genomes, a successful allopolyploid must have the ability to invoke and maintain diploid-like behavior, both cytologically and genetically. Recent studies on natural and synthetic polyploids have revealed many inconsistencies. Most species show non-Mendelian behavior in the polyploid, but others have not. Some species have demonstrated rapid genome changes following polyploid formation, while others have conserved progenitor genomes. Some have displayed directed, non-random genome changes, whereas others have shown random changes. Some of the genomic changes have appeared in the F1 hybrids, which have been caused by union of gametes from different progenitors, while other changes have been caused by genome doubling. Although these observations provide significant novel insights into the evolution of polyploids, the overall mechanisms of the event are still elusive. But, it appears that both genetic and epigenetic factors are involved in the diploidization process of polyploids. And, the overall genetic and epigenetic variations are often associated with the activities of repetitive sequences and transposon elements. Specifically, 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.