How to Make a Genetically Modified Plant

Genetically Modified Plants

• Definition: Plants altered by adding specific genes to change certain traits; referred to as transgenic plants.

Components Needed for Creation

• DNA Sequence: Contains the gene for the desired trait along with a promoter.

  • Can be from the same species, other species, or modified genes.

• Selection Marker: A way to identify which plants have the modification.

• Plant: The target organism for modification.

Examples of Genetic Modifications

• Virus Resistance: Papaya Ringspot Virus resistance via ringspot protein in Sunspot papayas.

• Insect Resistance: Bt traits in corn and cotton against borers and boll worms.

• Nutritional Enhancement: Golden Rice engineered for Vitamin A to prevent blindness.

• Herbicide Resistance: Allows extended farming using herbicides instead of manual weeding.

• Environmental Resilience: Modifications for drought or salinity tolerance.

• Physiological Changes: Adjusting size, growth duration, or browning in fruits.

Role of Promoters

• A promoter sequence is crucial for initiating the transcription process.

• Common Promoter: Cauliflower Mosaic Virus (CaMV35S) used in many genetically modified plants.

Plasmid Replication

• Plasmid Definition: Circular DNA that can be replicated in bacterial cells.

• Function: Enables mass production of target DNA for modification.

Selection Method

• Antibiotic Resistance Gene: Added to the plasmid to identify modified cells by growing them on antibiotic-containing plates.

Methods for DNA Introduction into Plants

• Gene Gun Method:

  • Fires DNA-coated gold particles into plant cells.

  • Non-specific insertion can cause damage and unpredictability.

• Agrobacterium-Mediated Transformation:

  • Utilizes the Ti plasmid from Agrobacterium tumefaciens to transfer DNA.

  • Produces less cellular damage and decreases chance of unwanted integration.

Ti Plasmid Structure

• Contains large segments involving:

  • Origin of Replication

  • Operons for activating multiple genes simultaneously.

  • Virulence Genes for effective DNA transfer.

  • Transfer DNA (T-DNA) for plant integration, marked by left/right borders.

Modification of Ti Plasmid for Transformation

• Harmful genes are removed; desired traits and strong promoters are added.

• Retains virulence genes for successful plant transformation.

Plant Transformation Process

• Plant cells release signaling molecules prompting Agrobacterium to express virulence genes.

• T-DNA is transferred to the plant cell, then incorporated into the plant genome.

Regeneration of Transgenic Plants

• Transformed cells are grown under sterile conditions in media with antibiotics and hormones.

• Only transformed cells grow and develop into whole plants.

Summary of Procedure

• Identify and prepare DNA sequence with a promoter.

• Integrate into plasmid with selection marker.

• Introduce DNA into plant cells using a gene gun or Agrobacterium.

• Select and regenerate plants under controlled conditions.