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Type: Journal article
Title: Instability of Plastid DNA in the Nuclear Genome
Author: Sheppard, A.
Timmis, J.
Citation: PLoS Genetics, 2009; 5(1):323-323
Publisher: Public Library of Science
Issue Date: 2009
ISSN: 1553-7390
Editor: Copenhaver, G.P.
Statement of
Anna E. Sheppard and Jeremy N. Timmis
Abstract: Functional gene transfer from the plastid (chloroplast) and mitochondrial genomes to the nucleus has been an important driving force in eukaryotic evolution. Non-functional DNA transfer is far more frequent, and the frequency of such transfers from the plastid to the nucleus has been determined experimentally in tobacco using transplastomic lines containing, in their plastid genome, a kanamycin resistance gene (neo) readymade for nuclear expression. Contrary to expectations, non-Mendelian segregation of the kanamycin resistance phenotype is seen in progeny of some lines in which neo has been transferred to the nuclear genome. Here, we provide a detailed analysis of the instability of kanamycin resistance in nine of these lines, and we show that it is due to deletion of neo. Four lines showed instability with variation between progeny derived from different areas of the same plant, suggesting a loss of neo during somatic cell division. One line showed a consistent reduction in the proportion of kanamycin-resistant progeny, suggesting a loss of neo during meiosis, and the remaining four lines were relatively stable. To avoid genomic enlargement, the high frequency of plastid DNA integration into the nuclear genome necessitates a counterbalancing removal process. This is the first demonstration of such loss involving a high proportion of recent nuclear integrants. We propose that insertion, deletion, and rearrangement of plastid sequences in the nuclear genome are important evolutionary processes in the generation of novel nuclear genes. This work is also relevant in the context of transgenic plant research and crop production, because similar processes to those described here may be involved in the loss of plant transgenes.
Keywords: Cell Nucleus
Plants, Genetically Modified
DNA, Chloroplast
Kanamycin Resistance
Base Sequence
Genome, Plant
Molecular Sequence Data
Genome, Plastid
Rights: Copyright: © 2009 Sheppard, Timmis. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI: 10.1371/journal.pgen.1000323
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Appears in Collections:Aurora harvest
Molecular and Biomedical Science publications

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