Minichromosome stability induced by partial genome duplication in Arabidopsis thaliana
Research Institute for Bioresources, Okayama University, Kurashiki, Japan.Chromosoma (Impact Factor: 4.6). 02/2010; 119(4):361-9. DOI: 10.1007/s00412-010-0259-8
Two partially reconstructed karyotypes (RK1 and RK2) of Arabidopsis thaliana have been established from a transformant, in which four structurally changed chromosomes (alpha, beta, gamma, and delta) were involved. Both karyotypes are composed of 12 chromosomes, 2n = 1" + 3" + 4" + 5" + alpha" + gamma" = 12 for RK1 and 2n = 3" + 4" + 5" + alpha" + beta" + gamma" = 12 for RK2, and these chromosome constitutions were relatively stable at least for three generations. Pairing at meiosis was limited to the homologues (1, 3, 4, 5, alpha, beta, or gamma), and no pairing occurred among non-homologous chromosomes in both karyotypes. For minichromosome alpha (mini alpha), precocious separation at metaphase I was frequently observed in RK2, as found for other minichromosomes, but was rare in RK1. This stable paring of mini alpha was possibly caused by duplication of the terminal tip of chromosome 1 that is characteristic of RK1.
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ABSTRACT: A dicentric ring minichromosome (miniδ) was identified in transgenic Arabidopsis thaliana and added to a wild type as a supernumerary chromosome. This line is relatively stable and has been maintained for generations, notwithstanding its ring and dicentric structure. To determine the mechanism for stable transmission of miniδ, the structure and behavior of two new types of ring minichromosomes (miniδ1 and miniδ1-1) derived from miniδ were investigated. Fluorescence in situ hybridization analysis revealed that miniδ1 is dicentric just like miniδ, whereas miniδ1-1 is monocentric. The estimated sizes of miniδ1 and miniδ1-1 were 3.8~5.0 and 1.7 Mb, respectively. The sizes of the two centromeres on miniδ1 were identical (ca. 270 kb) and similar to that of miniδ1-1 (ca. 250 kb). Miniδ1 was relatively stable during mitosis and meiosis, as is miniδ, whereas miniδ1-1 was unstable during mitosis, and the number of minichromosomes per cell varied. This possibly resulted from misdivision caused by a short centromere on monocentric miniδ1-1. Transmission through the female was quite limited for all three ring minichromosomes (0-3.2%), whereas that through the male was relatively high (15.4-27.3%) compared with that of other supernumerary chromosomes in Arabidopsis. Ring structure without telomeres itself seems not to limit the female transmission.
Chapter: Plant Centromere Biology[Show abstract] [Hide abstract]
ABSTRACT: This chapter contains sections titled: Centromere DNA structure Cytosine methylation and heterochromatin Centromere proteins Functional domains Future prospects and conclusions Acknowledgments References
Article: Engineered plant minichromosomes[Show abstract] [Hide abstract]
ABSTRACT: Minichromosomes offer an enormous potential for plant breeding and biotechnology, because they may simultaneously transfer and stably express multiple genes. Segregating independently of their host chromosomes, they provide a platform for accelerating plant breeding. Minichromosomes can be established from cloned components in vivo (bottom up) or via engineering of natural chromosomes (top down). When they possess functional centromeres and telomeres, they should be stably inherited, but their meiotic transmission rate is below that of endogenous chromosomes. To achieve the customized generation and control the regular transmission of minichromosomes are important challenges for applied research in chromosome biology. Here, construction and biology of plant minichromosomes are compared with data available for yeast and animal systems.
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