genetically modified plants
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Genetically Modified Plants. Biotechnology: underlying science Potential Risks vs. (Potential) Benefits. Assigned Reading: Chapter 10.5. Types of GMOs? artificial selection and traditional breeding, transgenic organisms, other approaches, targeted mutagenesis, gene introgression, ?. - PowerPoint PPT PresentationTRANSCRIPT
Genetically Modified Plants
Biotechnology: underlying scienceBiotechnology: underlying science
Potential Risks vs. (Potential) BenefitsPotential Risks vs. (Potential) Benefits
Assigned Reading: Chapter 10.5
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)
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.
Traditional Breeding
• technology is not essential,
• limited by species boundaries,
• all genes/traits are mixed.
~45,000 genes~25,000 genes
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.
Transgenic Plants
• based on DNA technology,• single genes/traits can be transferred,• species boundaries are not limiting.
How are GMOs generated?
insert into plant
…via biolistics - or - Agrobacterium tumefaceins
...uses tools of molecular genetics,
- i.e. applied bacteria and virus genetics.
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.
Agrobacterium
Plant CellsNature
Ti-Plasmid Transfer-DNA
Hormonegenes
Opinesgenes
Lab
Selectable Markers, etcAny Gene
Out: Ti genes, opine genes,
In: DNA of choice.
T-DNA
Ti: tumor inducing
Plasmid: extrachromosomal DNA evolved for genetic transfer.
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..
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 (2+): 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”.
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,
Gene Structure
chromosome
(megabases)
gene (kilobases)
...ata cgt act atc...
||| ||| ||| |||
...tat gca tga tag...
protein coding
...ttaggttctatc...
||||||||||||
...aatccaagatag...
promoter specific sequences.
Promoter Specifies Expression
General Promoter: all tissues, all the time.
Vegetative Promoter: no flower, no fruit expression.
Root Promoter: only root expression.
Expression = Protein Production
Protein and protein functions only present in tissue with active promoter.
Tissue Specific Expression
“Suicide” Promoters, etc.
Time Specific Expression
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 (?).
Potential Risks
• Risk of invasion.
• Direct nontarget Effects
• Indirect nontarget Effects.
• New Viral Diseases.
• Variability and Unexpected Results.
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.
Direct (nontarget)
• Risk to non-target species,
– pollinators, – passers-by,
• soil ecosystems,
– decomposition rates,– carbon cycle,– nitrogen cycle.
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.
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.
Variability and Unexpected Results
• time scale,
• numbers,
• environmental and cultivar differences,
• application, culture and consistency.
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.
Biotechnology in General
Scenario 1 Scenario 2
Bad Environmental Consequences
Negative impacts on,
• select species,• crops,• ecosystems,• etc.
Works great
Increase Carrying Capacity for Humans
Human Population Growth
Negative impacts on,
• select species,• crops,• ecosystems,• etc.
Transgenic Construct
pBacR: piggyback vector, transposon derived
3xP3-EGFP-S40: Green fluorescent protein, eye specific promoter
AgCP promoter: mosquito promoter, activated by blood feast.
SM14: SM1 DNA sequence repeated 4 times, linked
Signal: peptide sequence that sends protein to the midgut.