Journal of Heredity Advance Access originally published online on January 5, 2007
Journal of Heredity 2007 98(2):136-141; doi:10.1093/jhered/esl061
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Symposium Articles |
Evolution of Duplicate Gene Expression in Polyploid and Hybrid Plants
From the UBC Botanical Garden & Centre for Plant Research and Department of Botany, University of British Columbia, 6270 University Blvd, Vancouver, BC V6T 1Z4, Canada
Address correspondence to K. L. Adams at the address above, or e-mail: keitha{at}interchange.ubc.ca.
Allopolyploidy is a prominent mode of speciation in flowering plants. On allopolyploidy, genomic changes can take place, including chromosomal rearrangement and changes in gene expression; these processes continue over evolutionary time. Recent studies of gene expression in polyploid and hybrid plants, reviewed here, have examined expression in natural polyploids and synthetic neopolyploids as well as in diploid and F1 hybrids. Considerable changes in gene expression have been observed in allopolyploids, including up- or downregulation of expression in the polyploids compared with their parents, unequal expression of duplicated genes, and silencing of one copy. Genes in a variety of functional categories show altered expression, and the patterns vary considerably by gene. Some changes seem to be stochastic, whereas others are repeatable. Gene expression changes can be organ specific. Reciprocal silencing of duplicates in different organs has been observed, suggesting subfunctionalization and long-term retention of duplicates. It has become clear that hybridization has a much greater effect than chromosome doubling on gene expression in allopolyploids. Diploid and triploid F1 hybrids can show alterations of expression levels compared with their parents. Parent-of-origin effects on gene expression have been examined, and loss of gene imprinting has been shown. Some gene expression changes in polyploids and hybrids can be correlated with phenotypic effects. Demonstrated mechanisms of gene expression changes include DNA methylation, histone modifications, and antisense RNA. Several hypotheses have been proposed for why gene expression is altered in allopolyploids and hybrids.
Corresponding Editor: Loren Rieseberg
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