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Plant Biotechnology
Chapter 6
Fall 2008
CO2 + H2O →C6H12O6 + O2
Agriculture: The Next Revolution
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Biggest industry in the world ($1.3 trillion of
products per year)
Plant transgenesis allows innovations that are
impossible to achieve with conventional
hybridization methods (e.g. conventional ->
strength of cotton 1.5%; insertion of a single
gene > strength 60%!)
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Resistant to herbicides
Pest resistant
Vaccines
74% of all soybean crops are genetically
modified
32% of all corn
Methods Used in Plant
Transgenesis
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Unique advantages of plants:
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The long history of plant breeding provides plant
geneticists with a wealth of strains that can be
exploited at the molecular level
Plants produce large no.s of progeny; so rare
mutations and recombinations can be found more
easily
Plants have been regenerative capabilities, even
from one cell
Species boundaries and sexual compatibility are
no longer an issue
Protoplast Fusion (figure 6.2)
When injured, a mass of cells called a
callus may grow over the site
 Callus cells have the capability to
redifferentiate into shoots and roots
 Must remove the cellulose around these
cells before DNA can be introduced;
produce a protoplast
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Leaf Fragment Technique
(figures 6.3 & 6.4)
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Small discs of leaf incubated with genetically
modified Agrobacter Ti plasmid
Treat with hormones to stimulate shoot and
root development
Limitation: cannot infect monocotyledonous
plants only dicotyledonous such as tomatoes,
potatoes, apples and soybeans
Gene Guns
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Use on Agrobacter-resistant crops
Blast tiny metal beads coated with DNA into
an embryonic plant cell (figure 6.5)
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Aim at the nucleus or a chloroplast
Shoot in gene of interest and a gene marker
(reporter)
Why is it more advantageous to genetically
alter chloroplasts vs the nucleus?
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More genes can be inserted at one time, more
likely to be expressed, DNA is separate from the
nucleus (figure 6.6)
Antisense Technology
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Flavr SavrTM tomato introduced in 1994
Ripe tomatoes normally produce the enzyme,
polyglacturonase (PG) which digests pectin
Scientists isolated gene, produced a
complementary gene which produces a
complementary mRNA that binds to the
normal mRNA inactivating the normal mRNA
for this enzyme (figure 6.7)
RNA interference
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Inhibits gene expression by interfering with
transcription or translation of RNA molecules
http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html
Practical Applications in the
Field (table 6.1)
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Vaccines for Plants (figure 6.8)
Genetic Pesticides
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Bacillus thuringiensis (Bt)
Safe Storage (avidin-blocks the availability of
biotin for insects)
Herbicide Resistance –resistant to glyphosate
(figure 6.10)
Stronger fibers (already mentioned)
Enhanced Nutrition Golden Rice (vit A)
The Future: From
Pharmaceuticals to Fuel
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Plant-based petroleum for fuels,
alternatives to rubber, nicotine-free
tobacco, etc
Metabolic Engineering
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Manipulation of plant biochemistry to
produce nonprotein products or to alter
cellular properties
Health and Environmental
Concerns
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Human Health
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Allergens
Environment
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Super weeds