A transgenic crop plant contains a gene or genes which have been artificially inserted, instead of the plant acquiring them through pollination. The inserted gene sequence (known as the transgene) may come from another unrelated plant, or from a completely different species: for example, transgenic Bt corn, which produces its own insecticide, contains a gene from a bacterium. Plants containing transgenes are often called genetically modified or GM crops. What is the need of transgenic plants? A plant breeder tries to assemble a combination of genes in a crop plant which will make it as useful and productive as possible. The desirable genes may provide features such as higher yield or improved quality, pest or disease resistance, or tolerance to heat, cold and drought. This powerful tool enables plant breeders to do what they have always done - generate more useful and productive crop varieties containing new combinations of genes - but this approach expands the possibilities beyond the limitations imposed by traditional cross pollination and selection techniques.

1. Use of Transgenics
in crop production
Pragya Naithani
45979
PhD. AGRONOMY

2. 2
What are Transgenics ?
TRANSGENIC PLANTS- The plant whose genome is altered by
adding one or more transgenes are known as transgenic plants.
TRANSGENE- It is a foreign gene or genetic
material that has been transferred naturally or
by any of a number of genetic engineering
techniques from one organism to another.
TRANSGENESIS- The phenomenon of
introduction of exogenous DNA into the
genome to create and maintain a stable and
heritable character.

3. Why transgenic plants?
TRANSGENIC PLANTS
NUTRITIONAL
QUALITY
HERBICIDE
RESISTANCE INSECTICIDE
RESISTANCE
BIOTIC
STRESS
TOLERANCE
ABIOTIC
STRESS
TOLERANCE
ENHANCED
SELF LIFE
INDUSTRIAL
PRODUCT
PHARMACEUTICALS
&
VACCINES

4. Use of transgenics in crop production
RESISTANCE TO BIOTIC STRESS
Insect resistance
Virus resistance
Fungaland bacterial resistance
RESISTANCE TO ABIOTIC STRESS
Herbicide resistance
IMPROVEMENT OF CROP YIELD &QUALITY
Extended self life of fruits
Improved nutrition
Improved coloration
PRODUCTION OF LOW-COSTPHARMACEUTICALS
Edible vaccines
Essential proteins
PRODUCTION OF HYBRIDS
Male sterile lines

5. 1. Herbicide Resistance
Over 63% of transgenic crops grown globally have
herbicide resistance traits
Three approaches followed
1. Over production of herbicide sensitive biochemical compounds;
2. Structural alteration of a biochemical target compound resulting in
reduced herbicide affinity, and
3. Detoxification or degradation of the herbicide before it reaches the
biochemical target inside the plant cell.

6. A) Glyphosate Resistance
"Roundup Ready" soybean, maize, canola, sugar beet, cotton, and
alfalfa (wheat still under development)
Glyphosate kills plants by interfering with the shikimate pathway in plants,
which is essential for the synthesis of the aromatic amino
More specifically, glyphosate inhibits the enzyme 5-
enolpyruvylshikimate-3-phosphate synthase (EPSPS).
The gene encoding EPSPS has been transferred from glyphosate-
resistant E. coli into plants, which allows plants to be resistant

7. Also some micro-organisms have a version of EPSPS that is resistant to
glyphosate inhibition.
Gene isolated from Agrobacterium strain CP4 (CP4 EPSPS) that
produce an enzyme that inactivates glyphosate.
Glyphosate is rapidly metabolized by Glyphosate oxidoreductase
(GOX)

8. Glyphosate Sensitive Plants
Without amino acids, plant
dies
X
Fig: Glyphosate competes with the
PEP in the EPSPS catalysed
synthesis of enolpyruvylshikimate-
3- phosphate and inhibits
synthesis of tryptophan, tyrosine
and phenylalanine.

9. Glyphosate Resistant Plants
With amino acids, plant lives
Glyphosate oxidoreductase
++
++

10. b) Glufosinate Resistance
Glufosinate mimics the structure of the amino acid glutamine, which
blocks the enzyme glutamate synthase.
Plants receive a gene from the bacterium Streptomyces that produce a
protein that inactivates the herbicide.
c) Bromoxynil Resistance
A gene encoding the enzyme bromoxynil nitrilase (BXN) is
transferred from Klebsiella pneumoniae bacteria to plants.
Nitrilase inactivates the Bromoxynil before it kills the plant.

11. 2. Insect Resistance
Insect resistance in transgenic plants has been achieved through the use of
insect control protein genes of Bacillus thuringiensis.
Insect resistance was first reported in tobacco (Vaeck et al., 1987) and tomato
(Fischhoff et al., 1987).
More than 400 genes encoding toxins from wide range of B. thuringiensis have
been identified so far and approximately 40 different genes conferring insect
resistance have been incorporated into crops.

12. Bt toxin gene:
The toxins accumulate as crystal proteins (CS-endotoxins) inside
the plant.
They are converted to active form at high pH upon infection by
susceptible insect, thereby killing the insect
Based on their host range Hofte and Whiteley classified Bt toxins into
14 distinct groups and 4 classes (Hofte and Whiteley 1989) viz.
CryI (active against Lepidoptera)
CryII (Lepidoptera and Diptera)
CryIII (Coleoptera)
CryIV (Diptera).

13. Mode of action of Cry toxin
Mode of action of Bacillus thuringiensis in lepidopteran caterpillar:
1. ingestion by bacteria;
2. solubilization of the crystals;
3. activation protein;
4. binding of proteins to the receptors
5. membrane pore formation and cell disruption
Schünemann et al., 2014.

14. Transgenic plants: resistance to abiotic and biotic stresses :Akila Wijerathna- Yapa ;Journal of Agriculture and
Environment for International Development - JAEID 2017, 111(1): 245-275DOI: 10.12895/jaeid.20171.643

15. 3. Virus Resistance
Cross Protection
The concept of cross protection is the ability of one virus to prevent
or inhibit the effect of an infectious virus.
McKinney (1929) observed that in tobacco plants systemically
infected with a “light green strain” of Tobacco mosaic virus
(Tobamovirus), the appearance of yellow symptoms after re
inoculation with a TMV “yellow mosaic strain” was repressed
The resistance reduces numbers of infection sites on inoculated
leaves, suggesting that an initial step in the virus life cycle has been
disrupted.

16. This approach has been used in several crops like tobacco, tomato,
potato, rice, maize, melons, alfalfa, sugar beet etc.
Courtesy:Transgenic plants: resistance to abiotic and biotic stresses :Akila Wijerathna-Yapa ;Journal of
Agriculture and Environment for International Development - JAEID 2017, 111 (1): 245-275DOI:
10.12895/jaeid.20171.643

17. 4. Extended shelf life
• Transgenic tomato with delayed ripening: lower level of
ethylene production
• Reduced activity of the cell wall degrading enzymes, e.g.
Polygalacturonases
• The polygalactouronase gene is silenced.
• Plants were transformed with the anti-sense PG gene
• Anti sense mRNA pairs with sense mRNA, essentially blocking
the gene from expression.
• First genetically modified organism to be approved by the FDA,
in 1994.

18. The Flavr Savr Tomato
(First transgenic Plant Product)
Cited by: https://www.google.com/search?q=flavour+saver+tomato&source=lnms&tbm=isch&sa=X&
ved=0ahUKEwjqlduvbThAhW57nMBHephCCMQ_AUIDigB&biw=1500&bih=711&dpr=0.9#im grc=oSDrw5FBxewfTM:

19. Altered Oil Content
Strategies used for modifying fatty acids are as follows:
(i) introduction of a novel enzyme, e.g., an acyl transferase or an acyl-ACP
thioesterase, acyl-ACP desaturase,etc.,
(ii) suppression of an enzyme activity, e.g., α acyl-ACP desaturase
(iii) site-directed mutagenesis to alter the specificity, etc. of an enzyme, e.g.,
acyl-ACP desaturase, etc.
(iv) creation of hybrid genes to generate novel enzyme activities.
5. Improved nutrition

20. The most successful example is the increased lauric acid
content of B. napus; a transgenic line name 'Laurical’
The gene encoding lauroyl-ACP thioesterase was isolated
from California bay (Ullibellularia californica) and
transferred into B. napus. Some of the transgenic lines showed
upto 60% lauric acid in their oils.
Varieties of canola and soybean plants have been genetically
engineered to produce oils with better cooking and nutritional
properties.

21. Golden Rice- type of rice that
accumulates β-carotene in rice grains
(contains 37 mg/g of carotenoid of
which 84% is β-carotene)
Iron-enriched tomatoes with three
times the normal amount of beta-
carotene
Improved minerals and vitamins

22. Rice endosperm synthesize geranyl-
geranyl pyrophosphate which can
be converted into ß- carotene by 3
enzymes.
The transgenes providing these
enzyme activities were transferred
into rice through Agrobacterium
mediated transformation.
Golden rice

23. 5. 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
 Potatoes, banana, tomato, alfalfa, corn, and wheat are possible
candidates for use in livestock.
 Transgenic tobacco and potatoes were engineered to express
hepatitis B virus vaccine.

24. 6. Polymer production
• Plant seeds may be a potential source for plastics that could be produced and
easily extracted.
• A type of polymer called “poly-beta-hydroxybutyrate”, or PHB, is produced
in Arabidopsis or mustard plant.
• PHB can be made in canola seeds by the transfer of three genes from the
bacterium Alcaligenes eutrophus, which codes for enzymes in the PHB
synthesis pathway

25. Tearless onion produced by Gene Silencing
Colourful cauliflower
Purple tomatoes and purple rose
Colourful corns
7. Improved colours

26. Advantages of Transgenic crops:
• Can be a tool to adjust crop plants for changing climate
• Promising technique to feed increasing world population
• Improved quality
• High yield
• Economic containment of disease, insect, pest and weeds
• High adaptability

27. Disadvantages
• Hazardous chemicals through out the food chain,
Biomagnification
• Irreplaceable loss of flora and fauna, extinction of species and
set back to biodiversity
• Development of herbicide resistance in weeds (with free hand
use of herbicides)
• Soil and water pollution
• GHG emissions

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