Promiscuity in transgenic plants

Bergelson, Joy; Purrington, Colin B.; Wichmann, Gale

doi:10.1038/25626

Cited by 93 publications

(43 citation statements)

References 2 publications

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“…The species is structured into local races or types, and there is apparently low migration among populations. The estimated outcrossing rate of A. thaliana is less than 1% (Bergelson et al 1998;Tian et al 2002), and the migration rate among populations is likely to be substantially less unless seed dispersal among population is common. Figures 3-5 …”

Section: Combining Molecular and Phenotypic Datamentioning

confidence: 99%

Geographical Variation in Selection, from Phenotypes to Molecules

Kelly

2006

The American Naturalist

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Molecular technologies now allow researchers to isolate quantitative trait loci (QTLs) and measure patterns of gene sequence variation within chromosomal regions containing important polymorphisms. I develop a simulation model to investigate gene sequence evolution within genomic regions that harbor QTLs. The QTLs influence a trait experiencing geographical variation in selection, which is common in nature and produces obvious differentiation at the phenotypic level. Counter to expectations, the simulations suggest that selection can substantially affect quantitative genetic variation without altering the amount and pattern of molecular variation at sites closely linked to the QTLs. Even with large samples of gene sequences, the likelihood of rejecting neutrality is often low. The exception is situations where strong selection is combined with low migration among demes, conditions that may be common in many plant species. The results have implications for gene sequence surveys and, perhaps more generally, for interpreting the apparently weak connection between levels of molecular and quantitative trait variation within species.

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Section: Combining Molecular and Phenotypic Datamentioning

confidence: 99%

Geographical Variation in Selection, from Phenotypes to Molecules

Kelly

2006

The American Naturalist

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“…For one curve, an estimate of ϭ 2N e (1 Ϫ s)r (28) ϭ 6 ϫ 10 Ϫ4 is obtained from an estimate of r obtained from linear regression of six recombinant inbred markers near RPS5 (m488, mi372, mi443, SGCSNP246, ve006, and EG17G9; see www.arabidopsis.org͞). N e was estimated by dividing a genome-wide estimate of ϭ 2N e u ϭ 9 ϫ 10 Ϫ3 obtained as the average for the same eight Arabidopsis genes cited above, by u ϭ 1.5 ϫ 10 Ϫ8 estimated for Brassicaceae (29), and selfing rate s ϭ 0.996 (30).…”

Section: Ldmentioning

confidence: 99%

Signature of balancing selection in Arabidopsis

Tian

Araki

Stahl

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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243

239

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Natural selection and genetic linkage cause DNA segments to have genealogical histories resembling those of the selected sites. When a polymorphism maintained by selection is old, it will have an island of enhanced sequence variability surrounding it, which represents a detectable ''signature of selection.'' We investigate the structure of single-nucleotide polymorphisms (SNPs) in a 20-kb interval containing the Arabidopsis thaliana disease resistance gene RPS5, a locus containing common alleles for the presence͞ absence of the entire locus. The alleles are considerably diverged at surrounding sites, indicative of an old polymorphism maintained by selection. The island of ''enhanced'' variability extends several kilobases to either side of the RPS5 deletion junction, and these SNPs are in nearly complete linkage disequilibrium with the RPS5 insertion͞deletion. At a distance of 10 kb to either side of the locus, however, we find low levels of polymorphism and the absence of linkage disequilibrium between individual SNPs and RPS5 alleles. Our results show that the interval of enhanced variability surrounding this balanced polymorphism in Arabidopsis is large enough to be readily detected, but small enough to span the focal gene and few others. For this species it should be possible to identify the complete set of genes with long-lived polymorphisms, a potentially important subset of genes segregating for functional variants.B alanced polymorphisms are mutations maintained in populations by natural selection through heterozygote advantage, frequency-dependent selection, or spatial-temporal selection of alternative alleles. In contrast to strictly advantageous or deleterious mutations, whose persistence times as polymorphisms are generally short, balanced polymorphisms can be maintained indefinitely. They are also more likely to be segregating at intermediate frequencies, where they contribute most to population variance affecting fitness. Thus, there are good reasons to be interested in identifying balanced polymorphisms in a species.Under favorable circumstances, it is possible to infer the existence of a balanced polymorphism by examining the distribution of single-nucleotide polymorphisms (SNPs) within and between alleles. The magnitude of interallelic divergence of selectively neutral mutations can be related to the age of alleles; statistical tests have been developed to determine whether the age of a polymorphism is unusually large relative to selectively neutral expectations and hence is a candidate for a balanced polymorphism (1-3). This approach does not require prior knowledge of a gene's function, and it is not restricted to coding regions.Detailed studies of SNP have been conducted in both Drosophila and humans. These studies have not identified many new candidates for balanced polymorphisms, suggesting that this form of selection may contribute relatively little to the standing crop of functional variation within a species (refs. 4-7; for alternative approaches to detecting selection, see ref. 8). How...

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“…Promiscuity in transgenic plants by pollen has been reported and cited as a potential environmental risk (17,18). Genetically modified plants with a transgene integrated in the nucleus may be able to hybridize with sexually compatible species and give rise to hybrids and their progeny.…”

Section: Discussionmentioning

confidence: 99%

Protein trans-splicing in transgenic plant chloroplast: Reconstruction of herbicide resistance from split genes

Chin

Kim

Marin

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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Inteins are intervening protein sequences that undergo self-excision from a precursor protein with concomitant joining of the flanking sequences. Here, we demonstrate intein trans-splicing in Nicotiana tabacum chloroplasts by using the naturally split Ssp DnaE intein. Trans-splicing occurred whether both intein fragments were encoded in the chloroplast or were separated into the chloroplast and nuclear genomes. A biolistic approach was used to integrate two fusion genes, one encoding aminoglycoside-3-adenyltransferase (aadA) and the first 123 aa of the Ssp DnaE intein (In) and the other encoding 36 C-terminal amino acid residues of the Ssp DnaE intein (Ic) and soluble modified green fluorescent protein (smGFP) into N. tabacum plastids. Expression of these gene fragments in the chloroplast resulted in ligated aadA-smGFP due to In-Ic-mediated trans-splicing. Furthermore, an N-terminal portion of the herbicide resistance gene 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) containing a chloroplast localization signal fused to In (EPSPSn-In) was integrated into the nuclear DNA of N. tabacum by using Agrobacterium tumefaciensmediated transformation. The remaining EPSPS gene fragment (EPSPSc) fused to Ic (Ic-EPSPSc) was integrated into the chloroplast genome by homologous recombination. Western blot analysis of cell extracts from these plants showed a full-length EPSPS, demonstrating that the EPSPSn-In gene product migrated to the chloroplast and underwent trans-splicing. Furthermore, these transgenic plants displayed improved resistance to the herbicide N-(phosphonomethyl)-glycine (glyphosate) when compared with wild-type N. tabacum.I nteins are intervening protein sequences that undergo an autoexcision reaction, protein splicing, that results in ligation of the flanking protein regions, termed exteins (1). Inteins are present in the genome of eubacteria, eukaryota, and archaea, and to date, Ͼ100 have been identified (InBase: www.neb.com͞neb͞inteins. html; ref.2). The blue-green algae Synechocystis sp. PCC6803 has four inteins that are encoded within the dnaE, dnaB, dnaX, and gyrB genes. The dnaE gene encodes a split copy of the replicative DNA polymerase III catalytic ␣ subunit (DnaE), with the split portion separated by 745 kb of genomic DNA. The dnaE-n gene encodes the first 774 aa of DnaE and the dnaE-c gene encodes the remaining 423 aa of the DnaE protein. These two gene portions are transcribed from opposite strands of the genome. When translated, this split gene yields one polypeptide containing the N terminus of the DnaE (N-extein) fused to an intein fragment and a second fusion peptide containing the complementary intein fragment and the C terminus (C-extein) of the polymerase. The intein fragments of the fusion proteins assemble, then mediate a protein trans-splicing reaction, resulting in cleavage of both peptide bonds at the intein͞ polymerase junction and ligation of the flanking DnaE regions, giving rise to a mature, catalytically active DNA polymerase III catalytic ␣ subunit (3, 4).The intein porti...

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Promiscuity in transgenic plants

Cited by 93 publications

References 2 publications

Geographical Variation in Selection, from Phenotypes to Molecules

Geographical Variation in Selection, from Phenotypes to Molecules

Signature of balancing selection in Arabidopsis

Protein trans-splicing in transgenic plant chloroplast: Reconstruction of herbicide resistance from split genes

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