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Plants insect resistance (Bt), virus resistance - coat protein, satellites, herbicide resistance. Increasing shelf life of foods flavr savr tomatoes, control of seed germination, genetically modified foods

Plants insect resistance (Bt), virus resistance - coat protein, satellites, herbicide resistance. Increasing shelf life of foods flavr savr tomatoes, control of seed germination, genetically modified foods



Introduction


Genetic engineering involves the direct manipulation of genes to introduce desirable traits into plants. Through recombinant DNA technology, plants can be made resistant to insects, viruses and herbicides, show delayed ripening, controlled seed germination, and improved nutritional quality. These advances have revolutionized agriculture and food security.

1. Insect Resistance in Plants – Bt Technology

Bt (Bacillus thuringiensis)
Bacillus thuringiensis is a soil bacterium that produces Cry (crystal) proteins toxic to insects.
Mechanism of Bt Insect Resistance
Bt gene (cry gene) is isolated and transferred into plant genome.
Bt protein is produced in plant tissues.
When insects feed on Bt plants:
Cry protein is activated in alkaline insect gut.
It binds to gut epithelial cells.
Pore formation occurs → gut rupture → insect death.

Examples of Bt Crops
Bt cotton
Bt maize
Bt brinjal


Advantages

Reduced chemical pesticide use
Target-specific action
Environmentally safe
Increased crop yield
Limitations
Development of insect resistance
Biosafety concerns


2. Virus Resistance in Plants

A. Coat Protein–Mediated Resistance (CPMR)
Principle
Gene encoding viral coat protein is introduced into plants.
Expression of coat protein interferes with virus uncoating and replication.


Mechanism
Prevents virus disassembly
Inhibits replication and movement within plant
Example
Tobacco resistant to Tobacco Mosaic Virus (TMV)
Papaya resistant to Papaya Ring Spot Virus (PRSV)

B. Satellite RNA–Mediated Resistance

Satellite RNAs
Small RNA molecules dependent on helper viruses for replication.
Do not encode proteins.
Mechanism
Compete with viral genome for replication machinery.
Reduce viral multiplication and symptom severity.

Application

Used in virus-infected crops to reduce disease severity.

3. Herbicide Resistance in Plants


Definition

Herbicide-resistant plants tolerate specific herbicides that kill weeds but not the crop.
Methods
Modification of target enzyme
Introduction of herbicide-degrading genes.

Example

Glyphosate resistance via modified EPSP synthase gene.
Bar gene confers resistance to phosphinothricin

Advantages
Efficient weed control
Reduced tillage
Increased productivity
Limitations
Development of super weeds
Environmental concerns

4. Increasing Shelf Life of Foods – Flavr Savr Tomato


Flavr Savr Tomato
First genetically modified food approved for human consumption (1994).
Principle
Delayed fruit softening by inhibiting polygalacturonase (PG) enzyme.
Technique
Antisense RNA technology used to suppress PG gene expression.
Result
Slower cell wall degradation
Delayed ripening
Extended shelf life
Advantages
Improved storage and transport
Reduced post-harvest losses


5. Control of Seed Germination

Importance
Prevents premature germination (vivipary)
Synchronizes germination
Enhances seed storage life
Genetic Control
Manipulation of genes regulating abscisic acid (ABA) and gibberellic acid (GA).
Increased ABA → inhibits germination
Reduced GA → delays germination.


Applications

Crop management
Hybrid seed production
Storage stability

6. Genetically Modified Foods (GM Foods)


Definition

GM foods are foods derived from organisms whose genetic material has been altered using genetic engineering.

Examples

Golden rice (vitamin A enrichment)
Bt corn
Flavr Savr tomato
Herbicide-resistant soybean


Advantages

Improved nutritional quality
Enhanced shelf life
Pest and disease resistance
Reduced chemical usage


Concerns


Allergenicity
Gene transfer
Ethical and environmental issues


Conclusion
Genetic engineering has provided powerful tools to improve crop protection, yield, storage and nutritional quality. Technologies such as Bt insect resistance, virus resistance, herbicide resistance and delayed ripening contribute to sustainable agriculture and food security. However, careful evaluation, biosafety regulations and public awareness are essential for safe adoption of genetically modified foods.




MCQs: Genetic Engineering in Plants & GM Foods
1. Bt toxin is produced by
A. Bacillus subtilis
B. Bacillus thuringiensis
C. Agrobacterium tumefaciens
D. Pseudomonas fluorescens
Answer: B
2. Bt toxin proteins are also known as
A. Vip proteins
B. Cry proteins
C. Cap proteins
D. Shock proteins
Answer: B
3. Bt toxin becomes active in
A. Acidic gut of insects
B. Alkaline gut of insects
C. Neutral gut of mammals
D. Plant cytoplasm
Answer: B
4. Bt toxins kill insects by
A. Blocking respiration
B. Inhibiting protein synthesis
C. Creating pores in gut epithelium
D. Preventing molting
Answer: C
5. First commercially grown Bt crop in India
A. Bt maize
B. Bt rice
C. Bt cotton
D. Bt brinjal
Answer: C
6. Virus resistance through coat protein is known as
A. RNA interference
B. Antisense technology
C. Coat protein–mediated resistance
D. Satellite RNA resistance
Answer: C
7. Coat protein–mediated resistance works by
A. Killing virus particles
B. Preventing virus uncoating
C. Destroying host cell
D. Blocking transcription
Answer: B
8. First successful example of CPMR was in
A. Tomato
B. Tobacco
C. Potato
D. Papaya
Answer: B
9. Papaya Ring Spot Virus resistance was achieved using
A. Satellite RNA
B. Coat protein gene
C. Herbicide gene
D. Antisense RNA
Answer: B
10. Satellite RNAs are
A. Viral proteins
B. Independent viruses
C. Small RNAs dependent on helper virus
D. Bacterial plasmids
Answer: C
11. Satellite RNAs reduce viral infection by
A. Killing host cells
B. Enhancing viral replication
C. Competing with viral genome
D. Producing toxins
Answer: C
12. Herbicide resistance in plants allows
A. Weeds to grow faster
B. Crops to survive herbicide application
C. Herbicide breakdown in soil
D. Killing of beneficial microbes
Answer: B
13. Glyphosate targets which enzyme?
A. Rubisco
B. EPSP synthase
C. Nitrate reductase
D. ATP synthase
Answer: B
14. Herbicide resistance is achieved by
A. Removing plant enzymes
B. Modifying target enzyme
C. Stopping photosynthesis
D. Increasing respiration
Answer: B
15. Bar gene provides resistance to
A. Glyphosate
B. Paraquat
C. Phosphinothricin
D. Atrazine
Answer: C
16. Flavr Savr tomato shows
A. Faster ripening
B. Early seed germination
C. Delayed softening
D. Increased acidity
Answer: C
17. Flavr Savr tomato was developed using
A. RNAi
B. Antisense RNA technology
C. Gene knockout
D. CRISPR
Answer: B
18. Polygalacturonase enzyme is involved in
A. Protein synthesis
B. Cell wall degradation
C. Photosynthesis
D. Respiration
Answer: B
19. Delayed ripening in Flavr Savr tomato results in
A. Reduced shelf life
B. Extended shelf life
C. Faster spoilage
D. Poor taste
Answer: B
20. First genetically modified food approved for consumption
A. Golden rice
B. Bt corn
C. Flavr Savr tomato
D. GM soybean
Answer: C
21. Control of seed germination involves regulation of
A. Cytokinin only
B. Auxin only
C. ABA and GA
D. Ethylene only
Answer: C
22. Abscisic acid mainly
A. Promotes germination
B. Inhibits germination
C. Promotes flowering
D. Increases fruit ripening
Answer: B
23. Gibberellic acid mainly
A. Inhibits germination
B. Stops cell division
C. Promotes germination
D. Induces dormancy
Answer: C
24. Premature germination in seeds is called
A. Dormancy
B. Stratification
C. Vivipary
D. Scarification
Answer: C
25. Control of seed germination is useful in
A. Reducing crop yield
B. Hybrid seed production
C. Increasing weed growth
D. Decreasing storage life
Answer: B
26. Genetically modified foods are produced by
A. Traditional breeding
B. Hybridization
C. Recombinant DNA technology
D. Mutation breeding only
Answer: C
27. Golden rice is enriched with
A. Vitamin C
B. Vitamin A
C. Vitamin D
D. Vitamin K
Answer: B
28. GM foods help in
A. Increased chemical pesticide use
B. Reduced shelf life
C. Improved nutritional quality
D. Soil degradation
Answer: C
29. One major concern related to GM foods is
A. Increased yield
B. Reduced pesticide use
C. Allergenicity
D. Improved storage
Answer: C
30. Bt crops reduce
A. Herbicide use
B. Chemical insecticide use
C. Fertilizer use
D. Water requirement
Answer: B
31. Cry genes are originally isolated from
A. Viruses
B. Fungi
C. Bacteria
D. Plants
Answer: C
32. Insect resistance in plants mainly targets
A. Mammals
B. Birds
C. Insect pests
D. Microbes
Answer: C
33. Herbicide-resistant crops help in
A. Weed survival
B. Selective weed control
C. Soil erosion
D. Reduced yield
Answer: B
34. Satellite RNAs cannot
A. Replicate independently
B. Reduce virus severity
C. Depend on helper virus
D. Interfere with virus replication
Answer: A
35. Antisense RNA works by
A. Enhancing gene expression
B. Blocking mRNA translation
C. Increasing enzyme activity
D. Producing toxins
Answer: B
36. Which hormone promotes seed dormancy?
A. Auxin
B. Gibberellin
C. Abscisic acid
D. Cytokinin
Answer: C
37. Herbicide-resistant crops may lead to
A. Super weeds
B. Increased biodiversity
C. Reduced resistance
D. Crop sterility
Answer: A
38. Which GM crop is widely cultivated globally?
A. Bt cotton
B. Flavr Savr tomato
C. Golden rice
D. GM potato
Answer: A
39. Virus-resistant transgenic plants reduce
A. Nutritional value
B. Viral multiplication
C. Plant growth
D. Seed production
Answer: B
40. Bt toxin genes are expressed in
A. Roots only
B. Leaves only
C. All plant tissues
D. Selectively in tissues
Answer: D
41. CPMR mainly interferes with
A. Virus attachment
B. Virus uncoating
C. Host DNA replication
D. Cell division
Answer: B
42. Genetic engineering helps in shelf life extension by
A. Increasing ethylene production
B. Slowing fruit softening
C. Increasing respiration rate
D. Increasing water loss
Answer: B
43. GM foods are regulated mainly due to
A. Cost
B. Taste
C. Biosafety issues
D. Yield improvement
Answer: C
44. Herbicide resistance is often transferred using
A. Plasmids
B. Ribosomes
C. Lysosomes
D. Vacuoles
Answer: A
45. Cry proteins are toxic to
A. All organisms
B. Humans
C. Specific insect groups
D. Plants
Answer: C
46. Flavr Savr tomato reduces
A. Post-harvest losses
B. Photosynthesis
C. Flowering
D. Seed number
Answer: A
47. Genetic modification in seed germination helps to
A. Induce vivipary
B. Prevent vivipary
C. Increase seed spoilage
D. Reduce dormancy
Answer: B
48. Which is NOT a GM food example?
A. Golden rice
B. Bt corn
C. Flavr Savr tomato
D. Hybrid wheat
Answer: D
49. Virus resistance in plants improves
A. Disease susceptibility
B. Crop productivity
C. Weed growth
D. Seed dormancy
Answer: B
50. Main goal of genetic engineering in plants is
A. Increased chemical dependency
B. Sustainable agriculture
C. Reduced yield
D. Soil pollution
Answer: B

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