Plant Genetic Engineering

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Plant Genetic Engineering
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Genetic Engineering

• The process of manipulating and transferring
  instructions carried by genes from one cell to
  another

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THE SCIENCE OF GENETIC ENGINEERING
Isolate desired gene for a new trait from any
organism

Isolate plasmid DNA
Gene inserted into plasmid.
Introduce modified plasmid into bacterium for
replication.
Grow in culture to replicate.
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DNA of interest is EVERYWHERE
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Plant Genetic Engineering

• Product Concepts and Technical Feasibility
• Building the Transformant
• Plant Transformation
• Selection
• Plant Breeding
• Seed Production and Marketing
• Detection of GMO Crops in the Commodity Chain

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Plant transformation

• getting DNA into a cell
• getting it stably integrated
• getting a plant back from the cell

Requirement

• a suitable transformation method
• a means of screening for transformants
• an efficient regeneration system
• genes/constructs
• Vectors Promoter/terminator
• reporter genes selectable marker genes
• genes of interest

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Plant Transformation
DNA Delivery to Target Cells
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Transformation methods
DNA must be introduced into plant cells
Technique Methods
Indirect Agrobacterium mediated gene transfer Viral vector
Direct Lipid-mediated method, Calcium-phosphate mediated, Dextran-mediated, Electroporation, Biolistics, Polybrene, Laser transfection, Gene transfection enhanced by elevated temperature.
Method depends on plant type, cost, application
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Agrobacterium-mediated transformation

• Transformation by the help of agrobacterium

Agrobacterium is a natural genetic
engineer i.e. it transfers some of its DNA to
plants
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Agrobacterium tumefaciens
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Agrobacterium tumefaciens
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Biolistics

• gene gun
• DNA is coated onto gold (or tungsten) particles
  (inert)
• Gold is propelled by helium into plant cells
• if DNA goes into the nucleus it can be integrated
  into the plant chromosomes
• Cells can be regenerated to whole plants

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Gene Gun Technique
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Herbicide Resistance
A problem in agriculture is the reduced growth of
crops imposed by the presence of unwanted weeds.
Herbicides such as RoundupTM and Liberty LinkTM
are able to kill a wide range of weeds and have
the advantage of breaking down easily.
Development of herbicide resistant crops allows
the elimination of surrounding weeds without harm
to the crops.
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ROUNDUP (Glyphosate) TOLERANCE( HERBICIDE
TOLERANCE IN CROPS)
Glucose
ROUNDUP (Glyphosate )
3 phosphoglycerate
Tryptophan
Glycolysis
EPSP SYNTHASE
Phosphoenol pyruvate
Tyrosine
EPSP SYNTHASE
Phenylalaline
ROUNDUP (Glyphosate )
In transgenic plant, herbicide can not bind the
mutant of EPSP synthase (Example RR-Cotton,
RR-Soybean)
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Insect Resistance
Various insect resistant crops have been
produced. Most of these make use of the Cry gene
in the bacteria Bacillus thuringiensis (Bt) this
gene directs the production of a protein that
causes paralysis and death to many insects.
Corn hybrid susceptible to European corn borer
Corn hybrid with a Bt gene
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d -endotoxin gene (Cry gene) of Bacillus
thuriengenesis
GENE FOR Bt TOXIN WAS TRANSFERRED TO OBTAIN BT
TRANSGENIC PLANTS
PLANT SYNTHESIZES INACTIVE PROTOXIN
PROTEINASE DIGESTION IN INSECT GUT MAKES
THE ACTIVE TOXIN
INSECT FEEDS ON TRANSGENIC PLANT
Toxin binds a receptor on the gut epithelial
cells, forms a channel on the membrane. This
causes electrolyte leakage and insect death
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Virus Resistant Crops
Papaya infected with the papaya ringspot virus
Virus resistance gene introduced
The Freedom II squash has a modified coat protein
that confer resistance to zucchini yellows mosaic
virus and watermelon mosaic virus II. Scientists
are now trying to develop crops with as many as
five virus resistance genes
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Delayed Fruit Ripening

• Tomatoes are usually picked and sprayed with the
  plant hormone ethylene to induce ripening,
  although this does not improve taste
• Tomatoes have been engineered to produce less
  ethylene so they can develop more taste before
  ripening, and shipment to markets.
• It is produced by blocking the polygalacturonase
  (PG) gene, which is involved in spoilage. PG is
  an enzyme that breaks down pectin, which is found
  in plant cell walls.
• Plants were transformed with the anti-sense PG
  gene, which is mRNA that base pair with mRNA that
  the plant produces, essentially blocking the gene
  from translation.

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Flavr Savr tomato
Rot-Resistant Tomato Anti-sense gene ?
complementary to polygalacturonase (PG) PG
pectinase ? accelerates plant decay/rotting
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Golden Rice
Normal rice
Transgenic technology produced a type of rice
that accumulates beta-carotene in rice grains.
Once inside the body, beta-carotene is converted
to vitamin A.
Golden rice
Normal rice
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Gernayl Gernayl diphosphate (GGPP)
Phytoene synthase
Phytoene
Phytoene desaturase
Lycopene
Lycopene cyclase
Beta carotene
Complete biochemical pathway in the rice for
production of beta-carotene, a precursor for
vitamin A.
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Edible Vaccines
Edible vaccines are vaccines produced in plants
that can be administered directly through the
ingestion of plant materials containing the
vaccine. Eating the plant would then confer
immunity against diseases. The first human
clinical trial took place in 1997. Vaccine
against the toxin from the bacteria E.coli was
produced in potato. Ingestion of this transgenic
potato resulted in satisfactory vaccinations and
no adverse effects.
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Approved Transgenic plants

• Soybean
• Corn
• Cotton
• Oil Seed rape
• Sugarbeet
• Squash
• Tomato
• Tobacco

• Carnations
• Potato
• Flax
• Papaya
• Chicory
• Rice
• Melon

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