Address of Corresponding Author

Cytogenet Genome Res 2005;110:203-208 (DOI: 10.1159/000084953)

  Abstract.

Bacterial Artificial Chromosomes (BACs) derived from the B chromosome, based on homology with the B specific sequence, were subcloned and sequenced. Analysis of DNA sequence data indicated the presence of 23 common retroelements, as well as novel sequences of B chromosome origin. Generally, where the same retrotransposon type was observed in both A and B chromosomes, there were more copies per unit of sequence in the B centromeric region (the major site of B repeat) than in the A centromere, except for Huck-1. Based on previous estimates of the age of the major burst of transposition into the maize genome, the oldest retrotransposons (Ji-6 and Tekay, ~5.0 and 5.2 million years ago, respectively) were found in the B centromere region only, while the next two oldest (Huck-1 and Opie-1) were found in both the A and B sequences. Phylogenetic analysis of Opie retroelements from both A and B centromeres indicated that some of the B Opie centromeric sequences share a more recent common ancestor with A Opie retroelements than they do with other B Opie centromeric sequences. These results imply that the supernumerary maize B chromosome has coexisted with the A chromosomes during that period of transposition. They also support the hypothesis that the B chromosome had its origins from A chromosome elements, or that alternative origins, such as being donated to the maize genome in a wide species cross, preceded six million years ago, because the spectrum of retrotransposons in the two chromosomes is quite similar.   

Copyright © 2005 S. Karger AG, Basel

  Author Contacts

Request reprints from James A. Birchler
117 Tucker Hall, University of Missouri, Columbia, MO 65211 (USA)
telephone: 1-573-882-4905; fax: 1-573-882-0123
e-mail: BirchlerJ@Missouri.edu
Present address of T.P-D.: Cold Spring Harbor Laboratories
P.O. Box 100, Cold Spring Harbor, NY 11724 (USA)
Present address of S.M.: Harvard University Herbaria
22 Divinity Avenue, Cambridge, MA 02138 (USA).

  Article Information

Supported by a grant from the National Science Foundation Plant Genome Initiative (9975827).

Manuscript received 9 October 2003;
accepted in revised form for publication by J.-N. Volff 14 February 2004.
Number of Print Pages : 6
Number of Figures : 3, Number of Tables : 1, Number of References : 35