Genetic Modification of Plants I and II

Agrobacterium

• Agrobacterium is a genus of bacteria used in plant genetic engineering.

• It transfers DNA to the plant genome, crucial for the development of genetically modified plants.

Genetic Modification Techniques

Microprojectile Gun

• Also known as the "gene gun," a device that shoots microscopic gold or tungsten particles coated with DNA into plant cells.

• This method is used to create transformed plant cells that may develop into new plants.

Plant Cell Culture and Regeneration

• After transformation, cultured plant cells are regenerated into whole plants that can be acclimatized to grow in natural conditions.

Learning Objectives

• Understand the following topics:

  • Biotechnology in Agriculture

  • Differences: Selective Breeding vs. Genetically Modified (GM) Crops vs. Genome Edited Crops

  • The process of creating GM crops

  • The development of disease and pesticide resistant crops

Broccoli's Origin

• Broccoli is considered a man-made food, developed through selective breeding among wild cabbage plants.

• Selective breeding began around the 6th century BC.

• The term "broccoli" is derived from Italian meaning "the flowering crest of a cabbage."

Selective Breeding

Definition

• A natural and planned process where specific organisms are chosen to breed for favorable traits.

• Based on observable characteristics (phenotype).

Key Notes

• The exact genetic changes leading to desired phenotypes are often unknown.

• Broccoli is an example of a vegetable specifically developed using modern agricultural techniques.

Comparison of Breeding Methods

Selective Breeding

• A natural process conducted by farmers without recombinant DNA.

• Traits are selected based on phenotypic preferences.

Genetic Modification/Genome Editing

• Recognized as artificial processes involving precise modifications to the plant genome using recombinant DNA technology.

• Introduces specific traits that may not occur naturally.

Mutation Breeding

• An artificial method where seeds are exposed to chemicals or radiation to generate mutants with favorable traits.

Genome Editing

• Refers to techniques like CRISPR, where scientists alter the genomes without introducing foreign DNA.

U.S. Approved GM Crops

• A list of genetically modified crops that have received USDA approval includes:

  • Corn

  • Soybean

  • Cotton

  • Tomato

  • Papaya

  • Alfalfa

• Categorization includes traits such as insect resistance (IR), herbicide tolerance (HT), and drought tolerance (DT).

Major Biotech Crops Breakdown

• Soybean: 51%

• Maize: 30%

• Cotton: 13%

• Other crops account for the remaining percentage.

• Dominant traits in biotech crops are herbicide tolerance and stacked traits.

Insect Resistance Mechanism

• Bt gene from Bacillus thuringiensis produces proteins that kill specific pests, such as the European corn borer, by damaging their gut cells.

Herbicide Resistance Mechanism

• Genetically modified crops can survive herbicide sprays while weeds are killed, allowing for effective weed management.

Creation of Insect Resistant Tomato Plant

1. Cut out the insect resistance gene.

2. Insert it into a vector with an antibiotic resistance marker.

3. Use a gene gun to shoot the gene into plant cells.

4. Select cells incorporating the gene via antibiotic media.

Genome Editing via CRISPR

1. The Cas9 protein pairs with guide RNA and targets specific DNA sequences.

2. The complex cuts the DNA, allowing programmed DNA to be inserted.

Organic Certification

• Certified Organic means crops are grown without synthetic pesticides or fertilizers.

• Many brands promote "Non-GMO" or "organic" foods, emphasizing natural farming techniques.

PM - Biopesticides

• Bt (Bacillus thuringiensis) is used as a natural insecticide.

  • Effective against worms and caterpillars.

  • Safe for beneficial insects and humans.

GMOs Around the World

• Biotech crops planted in over 60 countries, with significant growth in developing nations.

• The U.S. remains a leader in biotech crop production, with many farmers adopting GMO varieties.

Conclusion

• The future of genetics in agriculture is shifting towards gene editing and sustainable practices, guided by regulations and societal acceptance.