Posted by: shrikantmantri | May 24, 2010

Plant Journal : Spatio-temporal patterns of genome evolution in allotetraploid species of the genus Oryza.

Spatio-temporal patterns of genome evolution in allotetraploid species of the genus Oryza.

Publication Date: 2010 May 6 PMID: 20487382
Authors: Ammiraju, J. S. – Fan, C. – Yu, Y. – Song, X. – Cranston, K. A. – Pontaroli, A. C. – Lu, F. – Sanyal, A. – Jiang, N. – Rambo, T. – Currie, J. – Collura, K. – Talag, J. – Bennetzen, J. L. – Chen, M. – Jackson, S. – Wing, R. A.
Journal: Plant J

SUMMARY Despite knowledge that polyploidy is wide-spread and a major evolutionary force for flowering plant diversification, detailed comparative molecular studies on polyploidy have been confined to only few species and families. The genus Oryza is composed of twenty-three species that are classified into 10 distinct "genome types" (6 diploid and 4 polyploid) and is emerging as a powerful new model system to study polyploidy. Here we report the identification, sequence and comprehensive comparative annotation of eight homoeologous genomes from a single orthologous region – Adh1-Adh2 – from four allopolyploid species representing each of the known Oryza genome types (BC, CD, HJ and KL). Detailed comparative phylogenomic analyses of these regions within and across species and ploidy levels, provided several insights into spatio-temporal dynamics of genome organization and evolution of this region in "natural" polyploids of Oryza. The major findings from this study are: a) homoeologous genomic regions within the same nucleus experienced both independent and parallel evolution; b) differential lineage specific selection pressures were not found between polyploids and their diploid progenitors; c) no dramatic structural changes relative to the diploid ancestors were detected; d) even though the BC and CD polyploid species appear to have arisen less than 2 MYA, molecular evolutionary rate variation between the two genomes in the BC complex species could be detected; and e) no clear distinction in the patterns of genome evolution in the diploid vs. polyploid species were detected.

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