Effective vectors including promoters, targeting sequences, terminators and selectable markers
Effective transformation systems.
Common Methods for Creating GM Crops
Agrobacterium method
Soil bacterium Agrobacterium tumefaciens is the causal agent of crown gall disease
A. tumefaciens infects the plant through its Ti plasmid. The Ti plasmid integrates a segment of its DNA, known as T-DNA, into the chromosomal DNA of its host plant cells
Particle gun method
Gene gun or a biolistic particle delivery system, is a device for injecting cells with DNA. The payload is an elemental particle of a heavy metal coated with plasmid DNA.
By 10 years later, almost all soybean in USA was Roundup- Ready
'Roundup-Ready' crops sprayed with glyphosate to keep clear of weeds
Glyphosate Use and Glyphosate-Resistant Weeds
1995-2014: 9× in agricultural glyphosate use in US (15× globally)
Since 1974, 8.6 billion kg of glyphosate have been applied globally
16 glyphosate-resistant weed species in Roundup-Ready® cropping systems
One resistance mechanism is over-production of EPSP synthase
Bollgard II® XtendFlex® is the first triple stack herbicide-tolerance technology in cotton, with tolerance to dicamba, glyphosate and glufosinate herbicides.
Bt Cotton
Cotton bollworm Helicoverpa armigera caterpillar on cotton
‘Cotton bollworm’ moth: worst single insect pest costing >$5 billion annually
‘Bt’ toxin gene (cloned from bacteria) in Monsanto’s ‘Bollgard II’ GM cotton
Used as organic pesticide
≈80% global cotton GM
Mechanism of Bt Toxin
"Cry" genes produce d-endotoxin crystals are solubilised in midgut and activated by proteolysis
Only functional part of gene used
Optimised for plant expression
Plants produce endotoxin
Only feeding insects killed
Traits in Engineered Crops
>30 traits currently engineered for commercial use
Most popular are herbicide tolerance, insect resistance and both together
Many other examples, e.g., papaya ringspot virus resistance or anthocyanin-rich biotech pink pineapple
Global Distribution of GM Crops (2018)
In 2018, global area of biotech crops was 191.7 million hectares, representing an increase of 1.1% from 2017, equivalent to 1.9 million hectares.
Top countries growing GM crops:
USA: 75.0 million hectares
Brazil: 51.3 million hectares
Argentina: 23.9 million hectares
Canada: 12.7 million hectares
India: 11.6 million hectares
Adoption of Biotech Crops in Brazil
Corn, winter
Corn, summer
Corn, total
Soybean
Cotton
Positive Impacts of GM Crops
Yield: 21.6% increase
Pesticide quantity: -36.9% decrease
Pesticide cost: -39.2% decrease
Total production cost: 3.3% increase
Farmer profit: 68.2% increase
Papaya Ringspot Virus (PRSV) in Hawaii
1992-1997
Virus spread by aphids kills trees
Production halved by end decade
Mechanism of Virus Resistance in GM Papaya
A gene from a virus, such as the papaya ringspot virus is engineered in the crop and is expressed forming segments of double-stranded (ds) RNA.
The dsRNAs trigger the plant's defense mechanism and are cleaved into short RNA molecules.
The short RNA molecules are complementary to the RNA from the virus. Again, these trigger the plant's defense mechanism and prevent the virus from replicating.
Transgenic Papaya and Controversy in Thailand
'Rainbow': GM papayas
Now 85% of Hawaiian papaya crop
Cornell University transferred virus resistance gene into Thai varieties of papaya
2004 field trials established in Thailand.
Local farmers ‘stole’ the fruit from the research stations
Greenpeace launches a campaign against the GM plants
Thai government destroys all the plants
Genome Editing
Definition: techniques for genome engineering that involve DNA repair mechanisms and/or replication for incorporating site-specific modification into a genomic DNA.
Genome engineering = process of introducing intentional changes into genomic DNA (ISO/DIS 5058-1).
Clustered regularly interspaced short palindromic repeats (CRISPR) coupled with a CRISPR-associated protein (Cas)
Oligonucleotide-directed mutagenesis (ODM)
Site-directed mutagenesis technique but does not use a targeted exonuclease
Timeline of Genome Editing Advancements
CRISPR/Cas system initially discovered E. coli genome in 1987, adapted system used to edited human and mouse cells in 2013
First GE humans born in China in October 2018 – twins Lulu and Nana (researcher fined and imprisoned)
First GE crop grown in USA in 2019
Cibus’ ultra-high-oleic oil canola
GE organism still classed as a GMO in EU, but not England
UK Legislation on Precision Bred Organisms
"Precision bred organism” means a precision bred plant or a precision bred animal.
An organism is "precision bred” if: every feature of its genome could have resulted from: traditional processes, whether or not in conjunction with selection techniques, or its genome does not contain any feature that results from the application of any artificial modification technique other than modern biotechnology.
GABA-Enriched Tomato
First CRISPR-edited food to enter market
Increased the amount of GABA in tomato
GABA (gamma-aminobutyric acid) is a neurotransmitter, a chemical messenger produced by the brain and nervous system.
Sanatech do not to claim that its tomatoes therapeutically lower blood pressure and promote relaxation.
Do advertise that consuming GABA, generally, can achieve these effects and that its tomatoes contain high levels of GABA.
High Vitamin D Tomato
Daily intake of vitamin D in adults in the UK is 7.2μg, below the RDA of 10μg
Researchers at the John Innes Centre (JIC) discovered that removing one gene encoding for the SL7-DR2 enzyme boosts vitamin D levels
Full RDA of an adult being obtained by the consumption of two small edited tomatoes
In the UK the Food Standards Agency approve new PBOs
Summary
‘GM’ plants altered in a way that does not occur naturally by mating and/or recombination
Major GM crops exploit pesticide technologies but diverse GM products appearing
Gene edited crops have reached market and soon to land in the UK