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Important Traits for Crop
Improvement
High crop yield
 High nutritional quality
 Abiotic stress tolerance
 Pest resistance
 Adaptation to inter-cropping
 Nitrogen Fixation
 Insensitivity to photo-period
 Elimination of toxic compounds

HYBRID DEVELOPMENT
FOR HIGHER YIELD
NUTRITIONAL
QUALITY
BIOTIC STRESS
TOLERANCE
TRANSGENIC PLANTS
ENHANCED
SHELF LIFE
ABIOTIC STRESS
TOLERANCE
INDUSTRIAL
PRODUCTS
PHARMACEUTICALS
& EDIBLE VACCINE
Tearless Onion
Colorful Cauliflowers
Purple tomatoes
Blue Roses
The big five successful traits
 Insect Resistance
 Delayed Fruit Ripening
 Nutritional Enhancing
 Herbicide Resistance
 Virus Resistance
Herbicide Resistance
 Glyphosate Resistance
i. Glyphosate = “Roundup”, “Tumbleweed” = Systemic herbicide
ii. Marketed under the name Roundup, glyphosate inhibits the enzyme
EPSPS (S-enolpyruvlshikimate-3 phosphate – involved in chloroplast
amino acid synthesis), makes aromatic amino acids.
iii. The gene encoding EPSPS has been transferred from glyphosateresistant E. coli into plants, allowing plants to be resistant.
 Glufosinate Resistance
i.
Glufosinate (the active ingredient being phosphinothricin) mimics the
structure of the amino acid glutamine, which blocks the enzyme
glutamate synthase.
ii. Plants receive a gene from the bacterium Streptomyces (bar gene) that
produce a protein that inactivates the herbicide.
Herbicide Resistance
 Bromoxynil Resistance
i. A gene encoding the enzyme bromoxynil nitrilase (BXN) is
transferred from Klebsiella pneumoniae bacteria to plants.
ii. Nitrilase inactivates the Bromoxynil before it kills the plant.
 Sulfonylurea.
i. Kills plants by blocking an enzyme needed for synthesis of
the amino acids valine, leucine, and isoleucine.
ii. Resistance generated by mutating a gene in tobacco plants
(acetolactate synthase), and transferring the mutated gene
into crop plants.
Roundup Ready™ Soybeans
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.
Insect resistance
Anti-Insect Strategy - Insecticides
a) Toxic crystal protein from Bacillus thuringensis



Toxic crystals found during sporulation
Alkaline protein degrades gut wall of lepidopteran larvae
• Corn borer catepillars
• Cotton bollworm catepillars
• Tobacco hornworm catepillars
• Gypsy moth larvae
Sprayed onto plants – but will wash off
The Bt toxin isolated from Bacillus thuringiensis has been used in plants.
The gene has been placed in corn, cotton, and potato, and has been
marketed.
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 with a Bt gene
Corn hybrid susceptible to European
corn borer
δ -endotoxin gene (Cry gene) of Bacillus thuriengenesis
GENE FOR Bt TOXIN WAS TRANSFERRED
TO OBTAIN BT TRANSGENIC PLANTS
PLANT SYNTHESIZES INACTIVE PROTOXIN
INSECT FEEDS ON
TRANSGENIC PLANT
PROTEINASE
DIGESTION IN
INSECT GUT
MAKES THE
ACTIVE TOXIN
Toxin binds a receptor on the gut epithelial cells, forms a channel
on the membrane. This causes electrolyte leakage and insect death
Virus resistance
a) Plants may be engineered with genes for resistance to viruses,
bacteria, and fungi.
b) Virus-resistant plants have a viral protein coat gene that is
overproduced, preventing the virus from reproducing in the host
cell, because the plant shuts off the virus’ protein coat gene in
response to the overproduction.
c) Coat protein genes are involved in resistance to diseases such as
cucumber mosaic virus, tobacco rattle virus, and potato virus X.
Delayed Fruit Ripening
a) Allow for crops, such as tomatoes, to have a higher shelf
life.
b) Tomatoes generally ripen and become soft during
shipment to a store.
c) Tomatoes are usually picked and sprayed with the plant
hormone ethylene to induce ripening, although this does
not improve taste
d) Tomatoes have been engineered to produce less
ethylene so they can develop more taste before ripening,
and shipment to markets
First biotech plant product – Flav’r Sav’r
tomato
“Rot-Resistant Tomato”
Anti-sense gene  complementary to polygalacturonase (PG)
PG = pectinase  accelerates plant decay/rotting
Nutritionally Enhanced
Plants
1.More than one third of the world’s population relies on
rice as a food staple, so rice is an attractive target for
enhancement.
2.Golden Rice was genetically engineered to produce high
levels of beta-carotene, which is a precursor to vitamin
A. Vitamin A is needed for proper eyesight.
3.Other enhanced crops include iron-enriched rice and
tomatoes with three times the normal amount of betacarotene
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.
“Normal” rice
“Golden” rice
Molecular Farming
1.A new field where plants and animals are genetically engineered to
produce important pharmaceuticals, vaccines, and other valuable
compounds.
2.Plants may possibly be used as bioreactors to mass-produce
chemicals that can accumulate within the cells until they are
harvested.
3.Soybeans have been used to produce monoclonal antibodies with
therapeutic value for the treatment of colon cancer. Drugs can
also be produced in rice, corn, and tobacco plants
4.Plants have been engineered to produce human antibodies against
HIV. Pharmaceuticals has begun clinical trials with herpes
antibodies produced in plants.
Why Plants?
Plants offer unique benefits for the production of
pharmaceutical proteins:

Ease of Scale-up



Low Cost
Reduced Capital Expenditures
No Animal Contaminants (virus)
Molecular Farming
(Vaccines)
a) Making plants that produce vaccines
b) Potatoes have been studied using a portion of the E.
coli enterotoxin in mice and humans.
c) Other candidates for edible vaccines include banana
and tomato, and alfalfa, corn, and wheat are possible
candidates for use in livestock.
d) Edible vaccines may lead to the eradication of
diseases such as hepatitis B and polio.
Edible Vaccines
One focus of current vaccine effort is on hepatitis B, a virus responsible for causing
chromic liver disease. Transgenic tobacco and potatoes were engineered to express
hepatitis B virus vaccine. During the past two years, vaccines against a E.coli toxin, the
respiratory syncytial virus, measles virus, and the Norwalk virus have been
successfully expressed in plants and delivered orally. These studies have supported the
potential of edible vaccines as preventive agents of many diseases.
There is hope to produce edible vaccines in bananas, which are grown extensively
throughout the developing world.