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