Genetically Modified Plants Biotechnology: underlying science Potential Risks vs.(Potential)...
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Transcript of Genetically Modified Plants Biotechnology: underlying science Potential Risks vs.(Potential)...
![Page 1: Genetically Modified Plants Biotechnology: underlying science Potential Risks vs.(Potential) Benefits Assigned Reading: Chapter 11.3.](https://reader036.fdocuments.us/reader036/viewer/2022062421/56649d3b5503460f94a15bf7/html5/thumbnails/1.jpg)
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Genetically Modified Plants
Biotechnology: underlying scienceBiotechnology: underlying science
Potential Risks vs.(Potential) BenefitsPotential Risks vs.(Potential) Benefits
Assigned Reading: Chapter 11.3
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Genetically Modified Organisms
Types of GMOs?
- artificial selection and traditional breeding,
- transgenic organisms,
- other approaches,
- targeted mutagenesis,- gene introgression,- ?
Old Science
Humans (~30,000 years)
Humans (~30 years)Bacteria (eons)
Humans (~15 years)Bacteria (eons)
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Desirable Agronomic Traits(traditional or modern)
• Increased yields, more nutritious, quality, etc.,
• More resistant to pestilence, weeds, water and nutrient deprivations,
• Ability to withstand marginal growth conditions,
– and thrive in new environmental ranges,
• Profit.
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Traditional Breeding
• technology is not essential,
• limited by species boundaries,
• all genes/traits are mixed.
~45,000 genes~25,000 genes
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Introgression
…incorporation of genes of one genome into the genome of another cultivar,
– standard breeding techniques are laborious (if possible at all),
– genomics and related sciences greatly accelerates standard breeding techniques*.
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Wild tomato
Genome Era Traditional Breeding
Cultivar w/ 1 wild gene replacement
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Transgenic Plants
• based on DNA technology,• single genes/traits can be transferred,• species boundaries are not limiting.
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How are GMOs generated?
insert into plant
…via biolistics - or - Agrobacterium tumefaceins
...uses tools of molecular genetics,
- i.e. applied bacteria and virus genetics.
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Biolistics
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Agrobacterium tumefaciens
Kalanchoe Stemw/ infection.
Natural soil bacterium Natural soil bacterium that infects plants,that infects plants,
hosts: 160 Genera,hosts: 160 Genera,families: > 60,families: > 60,
effecteffect; poor growth, ; poor growth, low yield.low yield.
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Agrobacterium
Plant CellsNature
Ti-Plasmid Transfer-DNA
Hormonegenes
Opinesgenes
Lab
Selectable MarkersGenes
Out: Ti genes, opine genes,
In: DNA of choice.
T-DNA
Ti: tumor inducing
Plasmid: extrachromosomal DNA evolved for genetic transfer.
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Construct T-DNA
infect plant, select for plants with T-DNA
T-DNA (Transfer DNA)
transform, select for agro with T-DNA
Agrobacterium
Plant chromosome with T-DNA insert.
…with gene of interest,
carotene,- herbicide resistance, etc..
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Construct T-DNA
selection genes
virulencegenes
T-DNA (Transfer DNA)
…gene of interest,
carotene,- herbicide resistance, etc..
Virulence genes: facilitate Agro infection, T-DNA transfer,
• not usually transferred in commercial applications,
Selection genes: used to identify transgenics,
• usually antibiotic or herbicide resistance, etc. (i.e. only the organisms with the T-DNA live in a selection experiment),
Gene of interest: protein coding region, plus a “promoter”.
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Promoters Control Expression
Transgenes must be expressed in order to function,
Promoters control where, when and how much protein is produced.
Foreign DNA is common (via nature) in most genomes,
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Gene Structure
chromosome
(megabases)
gene (kilobases)
...ata cgt act atc...
||| ||| ||| |||
...tat gca tga tag...
protein coding
...ttaggttctatc...
||||||||||||
...aatccaagatag...
promoter specific sequences.
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Promoter Specifies Expression
General Promoter: all tissues, all the time.
Vegetative Promoter: no flower, no fruit expression.
Root Promoter: only root expression.
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Expression = Protein Production
Protein and protein functions only present in tissue with active promoter.
Tissue Specific Expression
“Suicide” Promoters, etc.
Time Specific Expression
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Brief History of Transgenic Organisms
• Transgenic E. coli,
– not demonstratively dangerous,– demonstratively beneficial (probably).
• Transgenic virus,
– not demonstratively dangerous,– demonstratively beneficial (probably).
• Transgenic plants,
– demonstratively dangerous? (not yet),– demonstratively beneficial (?).
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Potential Risks
• Risk of invasion.
• Direct nontarget Effects
• Indirect nontarget Effects.
• New Viral Diseases.
• Variability and Unexpected Results.
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Potential Risks(risk of invasion)
• 50,000 invaders in USA the old fashioned ways,
– self-sustaining cultivars,• low anticipated risk,
– hybridization with (native) neighbors,
• transgene introgression,• introgression of domestic cultivar
genes with natives has occurred, resulting in negative impacts on native species,
– time lags.
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Direct (nontarget)
• Risk to non-target species,
– pollinators, – passers-by,
• soil ecosystems,
– decomposition rates,– carbon cycle,– nitrogen cycle.
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Indirect (nontarget)
• kill weeds = kill species that live “on” or eat the weeds,
• bioaccumulation,
– nontarget species eat plants, store toxins,
– those species are eaten, amassing the toxin,
– on up the food chain.
Bee on Red Clover.
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New Viral Diseases
• virus resistant plants promote virulent strains,
– mutations,– recombination,
• heteroencapsulation,
– virus move genes from one organism to another,
– not presently a risk, but a potential risk.
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Variability and Unexpected Results
• time scale,
• numbers,
• environmental and cultivar differences,
• application, culture and consistency.
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Other Issues
• Economic hegemony of GMP seed producing countries, companies,
• Cultural shifts in farming due to the introduction of GMOs,
• Potential allergies to genetically modified crops,
• The preservation of natural genetic crop-lines,
• The lack of an adequate risk assessment methodology to quantify unintended ecological consequences.
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The Precautionary Principle