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Christopher Preston

Publications and source records attributed to Christopher Preston.

5 recordsLinked to original sources
PubMed2025

Ectopic recombination: a novel mechanism of EPSPS gene amplification in glyphosate-resistant Chloris truncata.

Amplification of 5-enolpyruvylshikimate-3-P synthase (EPSPS) gene confers resistance to the herbicide glyphosate in the tetraploid Chloris truncata in Australia. To study the mechanism of amplification, the genomic organization of the EPSPS gene was investigated using fluorescence in situ hybridization (FISH) in one susceptible (Ct-S) and two resistant (Ct-R1 and Ct-R2) biotypes of C. truncata. FISH analysis revealed faint signals of the EPSPS gene on the telomeric regions of a single pair of homologous chromosomes in Ct-S plants. However, much brighter hybridization signals of the EPSPS gene were detected on three pairs of homologous chromosomes in Ct-R1 and on four pairs in the Ct-R2 plants. Thus, there was gene amplification on the native EPSPS locus as well as spread of EPSPS loci to additional chromosomes. All loci were detected in terminal regions which are hotspots of recombination. This local as well as ectopic EPSPS amplification to specific regions of chromosomes is a novel mechanism resistance to herbicides. We hypothesize that, during the bouquet stage of meiosis, telomeres come together forming a bouquet and this may provide an opportunity for ectopic recombination, supported by FISH analyses in interphase nuclei. Overall, the gene amplification appears to have occurred in two steps. First, there was tandem EPSPS amplification at the native locus, possibly via unequal recombination. Second, the amplified locus underwent ectopic recombination and spread to two additional chromosomes in Ct-R1 and three additional chromosomes in Ct-R2 plants.

Glyphosate↗
PubMed2003

Production of high-quality marketing applications: strategies for biotechnology companies working with contract research organizations.

Many biotechnology and pharmaceutical companies use clinical research organizations (CROs) to assist in the writing and preparation of clinical documents intended for submission to health authorities. Start-up companies often require the expertise of a CRO to prepare their first regulatory documents. Larger or more experienced companies often require CRO staff to assist at times of multiple simultaneous submissions. The timely production of high-quality new drug marketing applications requires close collaborations between the drug company and the CRO. The views of both CRO and industry in ensuring best practices are discussed.

Biotechnology↗
PubMed2003

Predicting the spread of herbicide resistance in Australian canola fields.

A common concern expressed about the commercial release of transgenic canola into cropping systems is the risks of unwanted gene flow between varieties. Experimental data is emerging that answers some of the theoretical questions that have been posed when considering gene flow on a landscape scale. This study developed models that utilise some of this published data in an attempt to quantify the spread of transgenes in a commercial farming system. The models, which included bootstrapping the empirical data and three mathematical simulations, were compared with each other and the published data. One of the mathematical models estimated average resistance frequency by imposing a Poisson distribution around the published mean value for a single transgenic field surrounded by conventional canola fields and the other two were derived from the theory that pollen flow decreased with distance in the form of a log decay curve. The predictions of all models suggested that the average frequency of resistance occurring from pollen flow in neighbouring canola fields, even when multiple transgenic fields are adjacent to the conventional fields, are likely to be below the current internationally accepted thresholds for contamination.

Australia↗
PubMed2002

Pollen-mediated movement of herbicide resistance between commercial canola fields.

There is considerable public and scientific debate for and against genetically modified (GM) crops. One of the first GM crops, Brassica napus (oilseed rape or canola) is now widely grown in North America, with proposed commercial release into Australia and Europe. Among concerns of opponents to these crops are claims that pollen movement will cause unacceptable levels of gene flow from GM to non-GM crops or to related weedy species, resulting in genetic pollution of the environment. Therefore, quantifying pollen-mediated gene flow is vital for assessing the environmental impact of GM crops. This study quantifies at a landscape level the gene flow that occurs from herbicide-resistant canola crops to nearby crops not containing herbicide resistance genes.

Acetolactate Synthase↗