Unit 5: Biotechnology

Introduction to Biotechnology

Biotechnology refers to the use of living organisms or their products for human welfare. It integrates biology with technology to develop products and processes that improve agriculture, health, industry, and the environment.

Tissue Culture and Micropropagation

Definition

Tissue culture is the technique of growing plant cells, tissues, or organs in an artificial nutrient medium under sterile conditions.

Micropropagation

Micropropagation involves growing plants from small tissue pieces (explants) to produce large numbers of identical plantlets.

Steps of Micropropagation

1. Explant selection – choosing a suitable plant part (e.g., node, leaf).
2. Sterilization – surface disinfection with agents like 0.1% mercuric chloride or ethanol.
3. Callus formation – induction of undifferentiated mass on agar medium containing auxins (e.g., 2,4‑D).
4. Organogenesis – differentiation of shoots or roots by adjusting hormone ratios (auxin:cytokinin).
5. Rooting – transfer to root‑inducing medium (often with IBA or NAA).
6. Acclimatization – gradual exposure to ambient conditions before field planting.

Applications

• Production of virus‑free plants.
• Rapid multiplication of elite genotypes.
• Conservation of rare and endangered species.
• Generation of somaclonal variation for breeding.

Example: Banana micropropagation yields thousands of disease‑free plantlets from a single shoot tip.

Plant Breeding

Traditional Methods

• Selection – choosing superior individuals based on phenotype.
• Hybridization – crossing two parents to combine desirable traits.
• Mutation breeding – inducing mutations with physical (gamma rays) or chemical (EMS) mutagens.

Modern Methods

• Molecular markers – DNA‑based tags (e.g., SSR, SNP) linked to traits.
• Marker‑Assisted Selection (MAS) – using markers to track genes during breeding cycles.

Breeding Goals

• Yield improvement.
• Disease resistance (bacterial, fungal, viral).
• Drought tolerance.
• Enhanced nutritional quality (e.g., high‑lysine maize, provitamin A rice).

Disease‑Resistant Plants

Breeding for Resistance

Conventional breeding incorporates resistance genes from wild relatives or mutated lines.

Examples

• Blight‑resistant wheat (e.g., varieties carrying Lr34 gene).
• Virus‑resistant papaya (transgenic coat‑protein gene).

Genetic Engineering Approach

• Bt crops – genes from Bacillus thuringiensis conferring insect resistance.
• Pathogen‑derived resistance – expressing viral coat protein or replicase to block infection.

Green Manure and Bio‑fertilizers

Green Manure

Green manure involves growing specific leguminous or non‑leguminous crops (e.g., Dhaincha (Sesbania aculeata), Sunnhemp (Crotalaria juncea)) and incorporating them into the soil while still green to increase organic matter.

Bio‑fertilizers

Bio‑fertilizers are preparations containing beneficial microorganisms that enhance nutrient availability.

Benefits

• Improved soil fertility and structure.
• Reduced dependence on chemical fertilizers.
• Environmentally sustainable.

Bio‑pesticides

Definition

Bio‑pesticides are biological agents used to control pests, including microorganisms, biochemicals, and beneficial insects.

Agents

• Trichoderma – fungus antagonistic to soil pathogens.
• Bacillus thuringiensis (Bt) – bacterium producing Cry toxins lethal to specific insect larvae.
• NPV (Nucleopolyhedrovirus) – virus infecting lepidopteran pests.

Other Strategies

• Pheromone traps – disrupt mating.
• Parasitoids – e.g., Trichogramma wasps parasitizing insect eggs.
• Predators – e.g., ladybird beetles feeding on aphids.

Benefits

• Eco‑friendly and biodegradable.
• Target‑specific, reducing non‑target effects.
• No harmful chemical residues in produce.

Genetic Engineering and GMOs

Process Overview

1. Gene isolation – extracting the gene of interest.
2. Vector construction – cloning the gene into a plasmid or viral vector.
3. Transformation – delivering the construct into host cells.
4. Selection – identifying transformed cells using marker genes (e.g., antibiotic resistance).
5. Regeneration – developing whole plants from transformed tissues.

Vectors

• Plasmids – circular DNA molecules.
• Ti plasmid of Agrobacterium tumefaciens – widely used for dicot transformation.
• Viral vectors – e.g., cauliflower mosaic virus (CaMV) for transient expression.

Transformation Methods

• Agrobacterium‑mediated – natural DNA transfer mechanism.
• Biolistics (gene gun) – high‑velocity metal particles coated with DNA.
• Electroporation – brief electric pulses increase membrane permeability.

GMOs

Genetically Modified Organisms (GMOs) are organisms whose genetic material has been altered using recombinant DNA technology. Transgenic plants and animals are common examples.

Applications

• Bt cotton – expresses Cry1Ac toxin, resistant to bollworm.
• Golden Rice – engineered to produce β‑carotene (provitamin A) in the endosperm.
• Insulin production – recombinant human insulin expressed in E. coli or yeast.
• Pharmaceuticals – vaccines, monoclonal antibodies, growth hormones.

Example Formula: Nitrogen Fixation by Rhizobium

The overall reaction can be represented as:

Where:

• N₂ – atmospheric nitrogen.
• H⁺ – protons.
• e⁻ – electrons supplied by ferredoxin.
• ATP – adenosine triphosphate, energy currency.
• NH₃ – ammonia, assimilated into amino acids.

Bio‑engineering

Bio‑engineering integrates genetic engineering, bioprocess engineering, and fermentation technology to design and optimize biological systems for industrial production.

Key Areas

• Genetic engineering – manipulation of DNA.
• Bioprocess engineering – design of reactors, downstream processing.
• Fermentation technology – large‑scale culture of microbes for metabolites (e.g., antibiotics, enzymes, biofuels).

Food Safety and Food Security

GMO Safety Concerns

• Allergenicity – potential introduction of new allergens.
• Gene flow – transfer of transgenes to wild relatives.
• Environmental impact – effects on non‑target organisms and biodiversity.

Labeling and Regulation

Many countries require mandatory labeling of GM foods and have regulatory frameworks (e.g., EFSA in Europe, USDA/FDA in the USA) to assess risk before release.

Role of Biotechnology in Food Security

• Improved crops – higher yields, stress tolerance.
• Reduced post‑harvest losses – delayed ripening, enhanced shelf life.
• Sustainable agriculture – lower chemical inputs, better resource use efficiency.