Analysis of multiple copies of geminiviral DNA in the genome of four closely related Nicotiana species suggest a unique integration event |
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Authors: | Ashby Mark K Warry Andrew Bejarano Eduardo R Khashoggi Alaa Burrell Michael Lichtenstein Conrad P |
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Institution: | (1) School of Biological Sciences, Queen Mary and Westfield College, University of London, London, E1 4NS, UK;(2) Department of Biochemistry, Imperial College of Science, Technology & Medicine, London, SW7 2AZ, UK;(3) Present address: Advanced Technologies (Cambridge) Ltd., Cambridge Science Park, Cambridge, CB4 4WA, UK;(4) Present address: Department of Biology, University College London, London, WC1E 6BT, UK;(5) Present address: Entomology and Nematology Department, IACR-Rothamsted, Harpenden, Herts, AL5 2JQ, UK;(6) Departmento de Biología Celular y Genética, Unidad de Genética, Campus Universitario de Teatinos 29017, Málaga, Spain |
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Abstract: | Previously, we discovered multiple direct repeats of geminivirus-related DNA (GRD) sequences clustered at a single chromosomal position in Nicotiana tabacum (tobacco). Here we show that, in addition to tobacco, multiple copies of these elements occur in the genomes of three related Nicotiana species, all in the section Tomentosae: N. tomentosiformis, N. tomentosa and N. kawakamii, but not in 9 other more distantly related Nicotiana species, nor in various other solanaceous and non-solanaecous plants. DNA sequence analysis of 18 GRD copies reveal 4 distinct, but highly related, sub-families: GRD5, GRD3 and GRD53 in tobacco; GRD5 in N. tomentosiformis and N. kawakamii; and GRD2 in N. tomentosa. In addition to novel sequences, all elements share significant but varying lengths of DNA sequence similarity with the geminiviral replication origin plus the adjacent rep gene. There is extended sequence similarity to REP protein at the deduced amino acid sequence level, including motifs associated with other rolling circle replication proteins. Our data suggest that all GRD elements descend from a unique geminiviral integration event, most likely in a common ancestor of these Tomentosae species. |
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Keywords: | integration geminivirus plant genomes evolution |
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