The allotetraploid Arabidopsis thaliana–Arabidopsis lyrata subsp. petraea as an alternative model system for the study of polyploidy in plants
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Polyploidy is known to be common in plants and recent work has focused on the rapid changes in genome structure and expression that occur upon polyploidization. In Arabidopsis, much of this work has been done on a synthetic allotetraploid obtained by crossing a tetraploid Arabidopsis thaliana (2n = 4x = 20) with A. arenosa (2n = 4x = 32). To explore an alternative route to polyploidy in this model species, we have developed a synthetic allopolyploid by crossing two diploid species: A. thaliana (2n = 2x = 10) and Arabidopsis lyrata subsp. petraea (2n = 2x = 16). F1 hybrids were easy to obtain and phenotypically more similar to A. lyrata. Spontaneous chromosome doubling events occurred in about 25% of the F1s, thus restoring fertility. The resulting allotetraploids (2n = 26) exhibited many genomic changes typically reported upon polyploidization. Nucleolar dominance was observed as only the A. lyrata rDNA loci were expressed in the F1 and allotetraploids. Changes in the degree of methylation were observed at almost 25% of the loci examined by MSAP analysis. Finally, structural genomic alterations did occur as a large deletion covering a significant portion of the upper arm of chromosome II was detected but no evidence of increased mobility of transposons was obtained. Such allotetraploids derived from two parents with sequenced (or soon to be sequenced) genomes offer much promise in elucidating the various changes that occur in newly synthesized polyploids.
KeywordsGenome shock Polyploids Allopolyploids Epigenetic changes DNA methylation
We wish to thank two reviewers for many helpful comments and suggestions. We also thank Dr. Clare Hasenkampf and Patricia Stronghill (University of Toronto-Scarborough) for their help with the cytological analysis of flower buds. This work was supported in part by a graduate studentship from the Fonds québécois de la recherche sur la nature et les technologies to J. Beaulieu. This work was also supported by a research grant from the Natural Sciences and Engineering Research Council to F. Belzile.
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