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Genomes behave as social entities: alien chromatin minorities evolve through specificities reduction
27 July 2010
Centro de Botânica Aplicada à Agricultura
Researchers from Instituto Superior de Agronomia, Technical University of Lisbon, Portugal, in collaboration with University of Missouri, Columbia, USA, studied the introgression of rye alien chromatin in wheat genome and showed that genomes behave like social entities.
In the manuscript that will be published in August issue of Theoretical and Applied Genetics the authors detected a high level of genomic restructuring events affecting rye chromosomes added to wheat genome through microsatellite and retrotransposon PCR-based molecular marker techniques. In another work (Bento et al 2008. PLoS ONE 3(1): e1402) the same authors had previously identified genomic alterations affecting preferentially rye genome in triticale, the hybrid genotype that results from the union of wheat and rye entire genomes.
Plant breeders commonly produce hybrid genotypes, through the cross of related species, to obtain improved varieties. This phenomenon – polyploidization - occurred also repeatedly during plant evolution. Triticale, the polyploid cereal that has been synthesized by the cross between wheat and rye, is one of the better studied polyploid model systems.
The novelty of this work, that may have important implication in future plant breeding strategies, is to show that genomes behave as social entities. In fact, reduced amounts of introgressed rye chromatin in wheat-rye addition lines, that possess only one rye chromosome pair, are more exposed to genomic restructuring than in triticale.
Genome restructuring events were previously detected in triticale, the polyploid species that possess wheat and rye entire genomes, involving rye repetitive sequences. Those genome alterations are even more drastic, including elimination of those sequences, in wheat-rye addition lines, that possess the wheat genome and a smaller fraction of rye genome (only one chromosome pair).
Rye sequences alterations are enhanced when the rye fraction introgressed in wheat genome is smaller in the addition lines (wheat plus rye chromosome pairs) in comparison to what happens in triticale (=wheat+rye).