Principles of Biotechnology: Herbicide Tolerance

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Questions and Answers

What are various strategies to make a plant herbicide tolerant?

Various strategies include genetic modification, selective breeding, and applying herbicide-resistant cultivars.

What is the mechanism of glyphosate-tolerant plants?

Glyphosate tolerance is achieved through gene expression alterations that enable plants to degrade glyphosate.

What are various direct transformation methods?

Direct transformation methods include microinjection, electroporation, and biolistics (particle bombardment).

What is cryopreservation?

Cryopreservation is the process of preserving cells or tissues at very low temperatures to maintain viability. Signup and view all the answers

What is star activity?

Star activity refers to the altered specificity of restriction enzymes due to changes in environmental conditions. Signup and view all the answers

What is a plasmid?

A plasmid is a small, circular piece of DNA found in bacteria, separate from chromosomal DNA. Signup and view all the answers

Define promoter and its types.

A promoter is a sequence of DNA that initiates transcription of a gene; types include strong, weak, and tissue-specific promoters. Signup and view all the answers

What are some properties of RNA to qualify as an enzyme?

RNA can catalyze reactions, bind substrates, and undergo structural changes. Signup and view all the answers

What are the important roles of CIMMYT and NBPGR in food security?

CIMMYT focuses on improving wheat and maize production while NBPGR conserves plant genetic resources. Signup and view all the answers

What is the importance of genetic diversity in crop plants?

Genetic diversity is vital for crop resilience, adaptability, and potential for future improvements. Signup and view all the answers

Differentiate land races from modern cultivars.

Land races are traditional varieties developed in specific environments, while modern cultivars are selectively bred for high yield and uniformity. Signup and view all the answers

What are selectable markers in transgenic plants?

Selectable markers are genes used to identify and select transformed cells during plant transformation. Signup and view all the answers

What is phytoremediation?

Phytoremediation is the use of plants to remove or stabilize contaminants in soil and water. Signup and view all the answers

What is the Citric Acid Cycle?

The Citric Acid Cycle, also known as the Krebs cycle, oxidizes acetyl-CoA into carbon dioxide and transfers energy to NADH and ATP. Signup and view all the answers

What is the role of the pentose phosphate pathway?

The pentose phosphate pathway generates NADPH and ribose-5-phosphate for cellular biosynthesis. Signup and view all the answers

What is the mechanism of absorption of minerals by plants?

Minerals are absorbed by plants through root hairs via active transport and diffusion. Signup and view all the answers

Study Notes

Principles of Biotechnology (PBT-502)

Herbicide Tolerance in Plants: Various strategies exist to create herbicide-tolerant plants, including:
- Metabolic Pathway Modification: Altering the enzyme targeted by the herbicide or introducing a herbicide-degrading enzyme
- Target Site Modification: Mutating the herbicide target site to reduce its sensitivity
- Gene Expression Regulation: Overexpressing genes that confer herbicide resistance
Glyphosate Tolerant Plants: Glyphosate inhibits the enzyme EPSPS, a crucial enzyme in aromatic amino acid biosynthesis. Glyphosate-tolerant plants express a modified EPSPS enzyme that is resistant to glyphosate inhibition. The vector used for transfection of the modified EPSPS gene often contains a strong promoter, a selectable marker (like antibiotic resistance), and T-DNA borders for integration into the plant genome.
Direct Transformation Methods: These methods directly introduce DNA into plant cells, bypassing the need for an intermediary.
- Calcium Phosphate Method: This method involves precipitating DNA with calcium phosphate, leading to DNA uptake by plant cells.
- Pollen-Mediated Gene Transfer: This method utilizes pollen to deliver the desired DNA to the plant's reproductive system.
- Other Direct Methods: Includes microinjection, electroporation, and biolistics (gene gun)

Transgenic Plant Production Technology (PBT-507)

RNA as an Enzyme (Ribozyme): RNA can act as an enzyme due to its ability to fold into specific three-dimensional structures that enable catalytic activity. Ribozymes are used to target specific mRNA sequences, preventing gene expression.
Gene Construct for Agrobacterium Transformation: This construct typically includes a selectable marker gene, a promoter driving gene expression, the transgene of interest, and T-DNA borders.
- Mechanism of Agrobacterium-Plant Interaction: The Agrobacterium T-DNA region is transferred into the plant cell through a process involving the vir genes.
  - vir Genes: These genes on the Ti plasmid are activated by plant wound signals, leading to the production of proteins necessary for T-DNA transfer.
  - T-DNA Integration: The T-DNA is integrated into the plant's genome, resulting in stable transformation.
  - Gene Expression: The transgene is then expressed under the control of the promoter.
Resistance to Insects: Several transgenes provide insect resistance. For example, cry genes derived from Bacillus thuringiensis (Bt) produce insecticidal proteins against specific insects.
- Low Expression of cry Genes: This can be due to factors such as:
  - Promoter Strength: The strength of the promoter used to drive cry gene expression can significantly impact expression levels.
  - Transcriptional Regulation: The plant's regulatory mechanisms might suppress cry gene transcription.
  - Post-Transcriptional Silencing: The cry mRNA might be targeted for degradation by the plant's cellular machinery.
Ti Plasmid Elements:
- T-DNA: This region carries genes responsible for plant hormone production and opine synthesis. These genes are transferred into the plant genome during transformation.
- vir Region: This region encompasses genes necessary for the T-DNA transfer process.
Promoter Types:
- Constitutive Promoters: These promoters are active in all cells and tissues, providing continuous gene expression.
- Tissue-Specific Promoters: These promoters are active only in specific cell types or tissues, allowing for targeted gene expression.
- Inducible Promoters: These promoters are activated only in response to specific environmental stimuli, enabling controlled gene expression.
Agrobacterium-Mediated Gene Transfer: This method utilizes the natural transformation ability of Agrobacterium to deliver the transgene of interest into plants.

Plant and Microbial Diversity (PBT-506)

CIMMYT and NBPGR:
- CIMMYT (International Maize and Wheat Improvement Center): Plays a critical role in improving maize and wheat varieties with a focus on yield, disease resistance, and nutrition.
- NBPGR (National Bureau of Plant Genetic Resources): Conserves and manages India's diverse plant genetic resources.
Genetic Diversity:
- Importance in Crop Plants: Genetic diversity is crucial for adaptation to various environmental conditions, disease resistance, and improved yield potential.
In-situ Conservation: Conservation of germplasm in its natural habitats.
- Merits: Maintains the genetic integrity of the species, allows natural selection to act on the population, and provides potential for future adaptation.
- Demerits: Requires significant land and resources, sensitive to human activities and environmental changes, and can be difficult to implement.
Land Races vs. Modern Cultivars:
- Land Races: Traditional varieties developed by farmers over generations, characterized by diversity and adaptation to local conditions.
- Modern Cultivars: High-yielding varieties developed through breeding programmes, often with increased uniformity but reduced genetic diversity.
- Merits and Demerits: While modern cultivars offer high yield potential, they are more susceptible to disease and environmental stress compared to land races with diverse genes.
Germplasm:
- Definition: A collection of plant genetic material, encompassing seeds, pollen, tissues, and DNA.
- Types:
  - Primary Gene Pool: Includes closely related species that can readily hybridize.
  - Secondary Gene Pool: Includes species more distantly related, requiring more sophisticated breeding techniques for hybridization.
  - Tertiary Gene Pool: Includes species very distant from the cultivated species, often requiring advanced genetic manipulation for successful hybridization.
Germplasm Activities of Research Agencies:
- These activities play a crucial role in crop improvement and food security by ensuring a diverse genetic reservoir for breeders to develop new varieties adapted to changing environments.

Molecular Approaches to Plant Physiology (PBT-511)

Phytoremediation: Using plants to remove pollutants from the environment.
- Mechanism: Plants can absorb, accumulate, and detoxify pollutants.
- Methods:
  - Phytoextraction: Plants extract pollutants from the soil and accumulate them in their tissues.
  - Phytostabilization: Plants prevent the movement of pollutants within the soil.
  - Phytodegradation: Plants break down pollutants into harmless substances.
- Importance: Sustainable and cost-effective method for environmental cleanup.
Energy Conserving Phase of Glycolysis:
- Mechanism: The energy-conserving phase involves ATP production using the energy derived from the breakdown of glucose. It involves the phosphorylation of ADP to ATP.
- Schematic Diagram: The energy-conserving phase includes the reactions of G3P to pyruvate, generating ATP and reducing power (NADH).
Citric Acid Cycle: This cycle occurs in the mitochondria and is a major pathway for energy production in plants.
- Oxidation of Pyruvate: The oxidation of one pyruvate molecule produces:
  - 3 CO2: Carbon dioxide is released as a byproduct.
  - 4 NADH: Reduced nicotinamide adenine dinucleotide (NADH) is produced, carrying electrons for oxidative phosphorylation.
  - 1 FADH2: Flavin adenine dinucleotide (FADH2) is produced, carrying electrons for oxidative phosphorylation.
  - 1 ATP: Adenosine triphosphate is produced through substrate-level phosphorylation.
Pentose Phosphate Pathway: This pathway generates NADPH, an important reducing agent used in various metabolic processes. It also produces pentose sugars necessary for nucleotide biosynthesis.
- Hexose Monophosphate Shunt: This is a component of the pentose phosphate pathway that produces NADPH and ribose-5-phosphate.
Seed Germination: The process of a seed developing into a seedling, requiring optimal conditions of water, oxygen, and temperature.
Seed Viability: The ability of a seed to germinate and develop into a plant.
Apoplast and Symplast: Two distinct pathways for water and solute transport within plants.
- Apoplast: The interconnected network of cell walls and intercellular spaces, allowing for rapid movement of water and solutes.
- Symplast: The interconnected network of cytoplasm within cells, connected by plasmodesmata.
Mineral and Water Absorption: Plants absorb minerals and water from the soil through their roots.
- Mechanism:
  - Active Transport: Uses energy to move minerals against their concentration gradient.
  - Passive Transport: Movement of water and minerals following their concentration gradient.
- Significance: Essential for plant growth and development.
Mitochondrial Electron Transport Chain:
- Succinate Dehydrogenase (Complex II): Involved in the oxidation of succinate to fumarate, contributing to the electron transport chain.
- Cytochrome bc1 Complex (Complex III): Transports electrons from ubiquinol to cytochrome c, pumping protons across the inner mitochondrial membrane.
Seed Dormancy: A state of suspended growth in a seed, preventing germination under unfavorable conditions.
Biochemical Effects Associated with Aerobic Glycolysis:
- Pasteur Effect: Inhibition of glycolysis in the presence of oxygen.
- Crabtree Effect: Inhibition of respiration by high glucose concentrations. This effect prevails in cancers.
- Warburg Effect: Elevated glycolysis in cancer cells, even in the presence of oxygen.

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Description

This quiz covers the principles of biotechnology related to herbicide tolerance in plants. Explore various strategies used to create herbicide-tolerant plants, focusing on metabolic pathway modification, target site modification, and gene expression regulation. Additionally, gain insights into glyphosate-tolerant plants and direct transformation methods.