Is supernumerary chromatin involved in gametophytic apomixis of polyploid plants? |
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| Authors: | Dominique Roche Wayne W Hanna Peggy Ozias-Akins |
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| Institution: | (1) U.S. Department of Agriculture, Agricultural Research Service, University of Georgia, Coastal Plain Experiment Station, Tifton, GA 31793-0748, USA, GE;(2) Department of Horticulture, University of Georgia, Coastal Plain Experiment Station, Tifton, GA 31793–0748, USA, GE;(3) Department of Plants Soils & Biometeorology, Utah State University, Logan UT 84322, USA e-mail: droche@mendel.usu.edu Fax: 1-435-797-3376, US |
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| Abstract: | Gametophytic apomixis, or unreduced embryo sac development that results in asexual reproduction through seeds, occurs in several
families of angiosperms and must be polyphyletic in origin. The molecular mechanisms underlying gametophytic apomixis have
not been discovered and are the subject of intense investigation. A common feature of almost all apomicts is their polyploid
nature. From genetic mapping studies in both monocots and dicots, there is low genetic recombination associated with a single
(rarely two), dominant locus for either aposporous or diplosporous embryo sac formation. In Pennisetum squamulatum and Cenchrus ciliaris, some DNA sequences mapping to the apospory locus are unique to apomictic genotypes and apparently hemizygous. This sequence
divergence at the apomixis locus could be a consequence of genome rearrangements and isolation from genetic recombination,
both of which may have contributed to the definition of a chromosomal region as supernumerary. The possible involvement of
supernumerary chromatin, formed as a result of interspecific hybridization, in the origin of apomixis, is explored here.
Received: 26 October 2000 / Revision accepted: 5 April 2001 |
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| Keywords: | Apomixis Genome rearrangements Hemizygosity Hybridization Polyploidy Supernumerary chromatin |
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