Transcript Plant Biotechnology

Plant Biotechnology
Plant Biotechnology
• Humans have been improving crop plants through
selective breeding for a long time
• Plant biotechnology allows scientists to transfer genetic
information in a more precise and controlled way
• Traditional plant breeding involves the crossing of
hundreds or thousands of genes
• Plant biotechnology allows for the transfer of only one or
a few desirable genes
– plant breeders can develop crops with specific beneficial traits
without the undesirable traits
Traditional Plant Breeding
Wild Corn
Domesticated Corn
Traditional Breeding
DNA is a strand
of genes, much
like a strand
of pearls.
Traditional plant
breeding
combines many
genes at once.
Donor plant
Commercial variety
X
Desired
Gene
New variety
(many genes transferred)
(crosses)
=
Desired gene
Plant Biotechnology
Using plant
biotechnology,
a single gene
may be added
to the strand.
Commercial variety New variety
(only desired gene transferred)
Desired gene
=
(transfers)
Desired gene
However, cloned DNA does not have to be from same species
Genetically Modified Organisms
(GMO’s)
• When a gene from one
organism is inserted
into another organism
to improve or change
the organism through
genetic engineering
techniques
– sometimes called
"transgenic"
GMO Debate
• Until recently, the European Union banned importation of GM crops.
• The US sued and won; importation of GM crops can no longer be
restricted
• British scientists have published a report indicating that GM crops may
damage the environment. Biotech opponents said this confirmed their
worst fears
Environmental and Ecological issues
Gene escape & development of “superweeds”
Impacts on non-target species
Insecticide
resistance
Loss of biodiversity
The first commercial transgenic plant was a
tomato variety that had reduced ethyleneDelaying ripening and allowing for longer
shipping time and shelf life.
Ripening control in tomato. Ethylene production in tomato has been reduced by
genetically modifying expression of the gene that encodes one of the enzymes responsible
for the ethylene biosynthesis. (a) The control tomatoes ripen normally between 53 and 59
days. The genetically modified (GM) tomatoes ripen extremely slowly during this same
period. (b) Graph showing ethylene production in control and GM tomatoes.
Virus-resistant Papaya: Farmers asked for help
Papaya, a tropical fruit high in vitamins C & A, is
an important food crop worldwide, and the 2nd
largest export crop in Hawaii.
A virus, papaya ringspot potyvirus (PRSV), had
wiped out papaya production on Oahu by the
1950’s.
The papaya industry moved to
Puna, Hawaii.
PRSV was discovered in
Puna in 1992, by late
1994, PRSV had spread
throughout Puna and
many farmers were going
out of business.
Virus-resistant
Papaya
Scientists at Cornell,
developed transgenic virusresistant papaya in 1986.
Transgenic
Non-transgenic
In transgenic papaya plants,
the coat protein of the virus
was engineered into the
papaya to create resistance,
similar to a vaccine.
Non-transgenic
Transgenic
Insect Resistance
Bacillus thuringiensis (Bt)
• Bacterium that produces crystal proteins,
which are toxic to many species of insects
• Widely used in crop plants, including
organic farms
• Thousands of different Bt strains
– produce over 200 crystal proteins
– active against various insects and some other
invertebrates
How Bt Works
1. Insect eats Bt crystals and
spores.
2. The toxin binds to specific
receptors in the gut and the
insects stops eating.
3. The crystals cause the gut wall
to break down, allowing
spores and normal gut
bacteria to enter the body.
4. The insect dies as spores and
gut bacteria proliferate in the
body.
Source: www.bt.ucsd.edu
Is Bt Safe to Use?
•
•
•
Bt is organic
Affects specific insects
Does not persist in the
environment
– poses no threat to groundwater
– breaks down under UV light of the
sun
•
EPA has not found any human
health hazards related to using Bt
– in the past 50 years, only two
incidents of an allergic reaction
have been reported to the EPA
– first genetically engineered plant,
corn, was registered with the EPA
in 1995 – now in cotton and potato
crops
•
Many insect species have
become resistant to Bt
Biofortified Food
• Millions of people suffer from
vitamin A deficiency, which leads to blindness and
increased susceptibility to diseases.
• Half of the world’s population eat rice as their
staple food, but rice grains do not contain vitamin
A or its immediate precursors.
• Humans can make vitamin A from carotenoids,
the yellow, orange, and red pigments of plants.
• In Golden Rice two genes have been inserted
into the rice genome to restart the carotenoid
biosynthetic pathway leading to the production
and accumulation of β-carotene in the grains
Golden Rice (1999)
Transgenic Plants as Bio-Reactors
Producing pharmaceuticals in plants is much less expensive
than using bacteria or human cell cultures, sterile
conditions, and fermentation technology
Plant
Derived
Oral
Vaccines
Examples:
• Potatoes for hepatitis B
• Bananas for cholera
• Lettuce for measles
Risks and Concerns- Human Health
• Is eating food from transgenic crops a health
hazard for humans?
– No evidence that it is. GMOs have been formally
evaluated as not ‘significantly’ different than
conventional crops plants in terms of their contents.
This implies that they are no more dangerous than
conventional crops.
• The specific proteins (e.g. BT) expressed in
transgenic crops are evaluated as potential health
hazards independently from their expression in
trangenic crops.
• GMOs are not tested for allergenicity
Risks and Concerns: Human Health
Brazil nuts and soybeans. To make soybeans more nutritionally complete, a
gene from Brazil nut was transferred to soybean. Many people are allergic to
Brazil nut, and it turned out that the chosen gene encoded a major allergen
from Brazil nut. When it was discovered that people who are allergic to Brazil
nuts could be now allergic to the GM soybeans, the project was stopped.
Risks & Concerns: Does pollen from Bt plants harm
Monarch Butterflies or other beneficial insects?
Corn Pollen and the Monarch
Butterfly
• Bt toxin in Bt Corn is effective in killing
Lepidopteron (moths) insects
• Monarch butterflies are Lepidopteran insects, so
they could be killed if exposed to the toxin
• A Nature article (1999) suggests that Bt corn
pollen harms monarch larvae
• However, in this case, Monarch butterfiles were
fed BT corn pollen and nothing else- they had to
eat the toxin and therefore were killed by it
Bt Corn Pollen and Monarch Butterfly
Facts:
-- Monarchs typically feed on milkweed not corn pollen
-- Conventional pesticides including natural Bt kill more Monarchs
-- Several field studies independently show that concentration of
Bt pollen adhering to milkweed plants within a few meters of the
Bt corn fields was too low to kill the butterflies
Poster Assignment
• Research ONE
genetically modified plant
• Include:
– Name of food
– Description of how the
plant is modified
– Purpose for genetically
modifying the plant
– Health Concerns
– Environmental Concerns
– Pictures
– Answer to Question:
Should GMO’s be labeled?
Explain.