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Plant Biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Genetic modification of plants is achieved by adding a specific gene or genes to a plant or by knocking out a gene with the RNA interference (RNAi) technique to produce a desirable phenotype. The plants resulting from adding a gene are often referred to as transgenic plants. If for genetic modification, genes of the species or of a crossable plant are used under the control of their native promoter, then they are called cisgenic plants. Genetic modification can produce a plant with the desired trait or traits faster than classical breeding because most the plant’s genome is not altered. To genetically modify a plant, a genetic construct must be designed so that the gene to be added or removed will be expressed by the plant. To do this, a promoter to drive transcription and a termination sequence to stop transcription of the new gene as well as the gene or genes of interest must be introduced into the plant. A marker for the selection of transformed plants is also included. In the laboratory, antibiotic resistance is a commonly used marker: plants that have been successfully transformed will grow on media containing antibiotics; plants that have not been transformed will die. In some instances, markers for selection are removed by backcrossing with the parent plant prior to commercial release. The construct can be inserted in the plant genome by genetic recombination using the bacteria A. tumefaciens or A. rhizogenes or by direct methods like the gene gun or microinjection. Using plant viruses to insert genetic constructs into plants is also a possibility, but the technique is limited by the host range of the virus. For example, CaMV only infects cauliflower and related species. Another limitation of viral vectors is that the virus is not usually passed on to the progeny, so every plant must be inoculated. The majority of commercially released transgenic plants are currently limited to plants that have introduced resistance to insect pests and herbicides. Insect resistance is achieved through incorporation of a gene from B. thuringiensis (Bt) that encodes a protein that is toxic to some insects. For example, when the cotton bollworm, a common cotton pest, feeds on Bt cotton it will ingest the toxin and die. Herbicides usually work by binding to certain plant enzymes and inhibiting their action. The enzymes that the herbicide inhibits are known as the herbicides target site. Herbicide resistance can be engineered into crops by expressing a version of target site protein that is not inhibited by the herbicide. This is the method used to produce glyphosate-resistant crop plants.
Agricultural biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Genetic modification of plants is achieved by adding a specific gene or genes to a plant, or by knocking out a gene with RNA interference (RNAi) technique, to produce a desirable phenotype. The plants resulting from adding a gene are often referred to as transgenic plants. If for genetic modification, genes of the species or of a crossable plant are used under the control of their native promoter, then they are called cisgenic plants. Genetic modification can produce a plant with the desired trait or traits faster than classical breeding because the majority of the plant’s genome is not altered. To genetically modify a plant, a genetic construct must be designed so that the gene to be added or removed will be expressed by the plant. To do this, a promoter to drive transcription and a termination sequence to stop transcription of the new gene and the gene or genes of interest must be introduced to the plant. A marker for the selection of transformed plants is also included. In the laboratory, antibiotic resistance is a commonly used marker: plants that have been successfully transformed will grow on media containing antibiotics; plants that have not been transformed will die. In some instances, markers for selection are removed by backcrossing with the parent plant prior to commercial release. The construct can be inserted in the plant genome by genetic recombination using the bacteria A. tumefaciens or A. rhizogenes, or by direct methods like the gene gun or microinjection. Using plant viruses to insert genetic constructs into plants is also a possibility, but the technique is limited by the host range of the virus. For example, CaMV only infects cauliflower and related species. Another limitation of viral vectors is that the virus is not usually passed on to the progeny, so every plant has to be inoculated. The majority of commercially released transgenic plants are currently limited to plants that have introduced resistance to insect pests and herbicides. Insect resistance is achieved through incorporation of a gene from B. thuringiensis (Bt) that encodes a protein that is toxic to some insects. For example, when the cotton bollworm, a common cotton pest, feeds on Bt cotton, it will ingest the toxin and die. Herbicides usually work by binding to certain plant enzymes and inhibiting their action. The enzymes that the herbicide inhibits are known as the herbicide’s target site. Herbicide resistance can be engineered into crops by expressing a version of target site protein that is not inhibited by the herbicide. This is the method used to produce glyphosate-resistant crop plants.
Harnessing gene drive
Published in Journal of Responsible Innovation, 2018
John Min, Andrea L. Smidler, Devora Najjar, Kevin M. Esvelt
Second, people are more likely to support interventions that can be at least partly undone if something goes wrong. Full sequence reversibility is exclusive to certain threshold-dependent and combined drive systems and will be most attractive to people wary of permanently ‘contaminating’ nature. Such individuals may also support ‘cisgenic’ interventions that harness meiotic gene drives native to the species of interest, or costly self-exhausting drive systems that will be naturally purged from the population if not actively maintained through periodic releases. For the probable civic majority who do not place intrinsic value upon the original sequence, the faster spread of reversal drive systems based on CRISPR or possibly Medea-based systems could be a major advantage. Truly irreversible drive systems are unlikely to win support.