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First published online August 13, 2009; doi:10.3732/ajb.0800270 American Journal of Botany 96: 1656-1664 (2009) © 2009 Botanical Society of America, Inc.

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Mitotic instability in resynthesized and natural polyploids of the genus Arabidopsis (Brassicaceae)¹

² Department of Biology, University of Puget Sound, Tacoma, Washington 98416 USA ³ Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211-7310 USA

ABSTRACT

Allopolyploids contain complete sets of chromosomes from two or more different progenitor species. Because allopolyploid hybridization can lead to speciation, allopolyploidy is an important mechanism in evolution. Meiotic instability in early-generation allopolyploids contributes to high lethality, but less is known about mitotic fidelity in allopolyploids. We compared mitotic stability in resynthesized Arabidopsis suecica-like neoallopolyploids with that in 13 natural lines of A. suecica (2n = 4x = 26). We used fluorescent in situ hybridization to distinguish the chromosomal contribution of each progenitor, A. thaliana (2n = 2x =10) and A. arenosa (2n = 4x = 32). Surprisingly, cells of the paternal parent A. arenosa had substantial aneuploidy, while cells of the maternal parent A. thaliana were more stable. Both natural and resynthesized allopolyploids had low to intermediate levels of aneuploidy. Our data suggest that polyploidy in Arabidopsis is correlated with aneuploidy, but varies in frequency by species. The chromosomal composition in aneuploid cells within individuals was variable, suggesting somatic mosaicisms of cell lineages, rather than the formation of distinct, stable cytotypes. Our results suggest that somatic aneuploidy can be tolerated in Arabidopsis polyploids, but there is no evidence that this type of aneuploidy leads to stable novel cytotypes.

Key Words: allopolyploid • allopolyploidization • aneuploid • Arabidopsis suecica • Arabidopsis arenosa • Brassicaceae • FISH • fluorescent in situ hybridization • hybrid • mitotic instability • mitosis

Received for publication 7 August 2008. Accepted for publication 27 April 2009.

FOOTNOTES

¹ The authors thank M. Morrison and S. Bennett for technical and logistical help with the plant growth facilities; L. Comai, J. Birchler, R. Martienssen, and the entire Polyploidy Consortium for stimulating discussions; and M. R. Lamb for careful reading of an earlier version of the manuscript. They also thank two anonymous reviewers for comments that significantly improved the manuscript, and M. Jost for help with figures. This study was supported by NSF Plant Genome grant DBI-0501712 to J.C.P. and A.M., NSF Major Research Instrumentation grant MRI-0619009 to A.M., and funds from the University of Puget Sound Enrichment Committee to K.M.W. and A.M.

⁴ Author for correspondence (amadlung{at}ups.edu)

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