GMOs and Plant Biology Notes

GMOs

• All living organisms are genetically modified to some extent.

  • Sexual reproduction intentionally modifies genetic material, leading to variation.

  • Even asexual organisms like bacteria undergo random genetic mutations that introduce variation.

  • Mutation: Accidental change to the DNA sequence.

• GMOs, genetic engineering, and genetic modification often refer to human-introduced modifications.

• World Health Organization (WHO) Definition of GMO: "organism(s) in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating or mutations."

  • Variation in GMOs results from lab-based genetic manipulation, not natural processes.

• Genetic engineering: Lab-based technology to alter DNA of an organism.

• Transgenic organism: DNA modified by inserting a gene from a different species.

  • "trans-" means "across."

  • Example: Corn modified with a bacterial gene.

• Cisgenic GMOs: Donor gene inserted from the same species.

  • "cis-" means "the same."

• Humans have been altering genetics of other organisms for a long time (e.g., dogs, wheat, strawberries).

• GMO stands for genetically modified organisms

Selective Breeding (Artificial Selection)

• Humans identify natural variation in a trait and breed individuals with similar characteristics.

• Gregor Mendel: Used selective breeding in pea plants to develop "true-breeding" versions with specific traits.

Flavr-savr Tomato

• First GMO approved for human consumption (1994).

• Invented by Calgene to solve the problem of fruit over-ripening.

Why GMOs?

• Address demands on Earth's resources due to population increase and technological development.

• Climate change: Produce crops that can withstand climate change.

• Pest management: Produce crops that are resistant to pests.

• Production of biotechnology products:

  • GM bacteria used to produce medicines and pharmaceutical compounds.

  • Example: Human insulin.

  • GM bacteria also produce vaccines (e.g., hepatitis B), clotting factors, human growth hormone, and interferons.

Protection of Plants

• Bacteria engineered to produce proteins that protect plants from freezing.

• Bacillus thuringiensis (Bt) bacteria: Chemicals inserted into plants to protect them from insect predation.

Bioremediation

• Using organisms to clean the environment.

• GM bacteria enhance enzymes and metabolic pathways to break down toxic chemicals.

  • Used for oil spills and mercury contamination.

Synthesis of Organic Chemicals

• GM bacteria and algae produce biofuels and other organic chemicals for manufacturing.

Genetic Modification in Animals

• Purposes:

  • Produce products for humans.

  • Provide disease resistance.

  • Study human diseases.

  • Enhance physiology.

Models for Human Disease

• Animals (e.g., mice) make excellent models.

• Human genes associated with diseases (e.g., cancer, cystic fibrosis) are inserted into animals to study new treatments.

Biotechnology Products (Animals)

• GM animals (e.g., goats, mice, chickens) express proteins or pharmaceutical compounds in their meat, milk, or eggs.

Increased Nutritional Value (Animals)

• Genetically modified to:

  • Reduce disease susceptibility.

  • Increase growth rate.

  • Improve meat or milk quality.

• AquaAdvantage Salmon: First GM animal approved for human consumption.

Xenotransplantation

• Genetically engineering pigs to provide organs (e.g., liver, kidney, bone marrow) for human transplants.

Genetic Modification in Plants

• Purposes:

  • Herbicide tolerance (e.g., soybeans).

  • Insect resistance.

GM Crop Plants Available in the United States (Table 1.1)

• Squash (1995): Disease resistance

• Cotton (1996): Insect resistance; herbicide tolerance

• Soybean (1995): Insect resistance; herbicide tolerance

• Corn (1996): Insect resistance; herbicide tolerance; drought tolerance

• Papaya (1997): Disease resistance

• Canola (1999): Herbicide tolerance

• Alfalfa (2006): Herbicide tolerance

• Sugar beets (2006): Herbicide tolerance

• Potato (2016): Reduced bruising; non-browning; reduced acrylamide; blight (fungus) resistant

• Apples (2017): Non-browning

• Rice (2018): Increased nutritional content

Plants

• Multicellular, autotrophic eukaryotes that use photosynthesis.

• Evolved from green algae.

• Close relatives of red algae and green algae; charophyte algae are considered their sister group.

• Charophytes may have given rise to modern plants.

• Green algae share molecular features with plants:

  • DNA sequences show close evolutionary relationship.

  • Chloroplasts contain same pigments.

  • Cell walls contain cellulose.

  • Use starch as a storage molecule.

• Four major groups of plants:

  • Bryophytes: Nonvascular plants.

  • Seedless vascular plants.

  • Gymnosperms: "Naked seeds"; seeds in cones or completely exposed.

  • Angiosperms: Flowering and fruit plants.

Alternation of Generations

• Life cycle with alternating diploid and haploid generations.

  • Diploid generation: Multicellular sporophyte produces spores (haploid cells with thick walls) by meiosis.

  • Spores germinate, undergo mitosis, and grow into multicelled haploid gametophytes that produce gametes by mitosis.

  • Male and female gametes meet (fertilization), forming a diploid zygote which undergoes mitosis and develops into a new sporophyte.

Adaptations to Life on Land

• Water conserving features:

  • Cuticle: Waxy covering that reduces evaporative water loss.

  • Stomata: Closable pores that allow gas exchange for photosynthesis; close in dry weather to reduce water loss.

Vascular Tissue

• Vascular plants require vascular tissues to move substances from roots to body regions.

  • Xylem: Distributes water and mineral ions.

  • Phloem: Distributes sugars made in photosynthetic cells.

  • Lignin: Stiffens the walls of xylem cells, providing structural support.

Leaves and Roots

• Leaves: Increase surface area for intercepting sunlight and gas exchange; contain veins of vascular tissue.

  • Main function: Photosynthesis.

  • True leaves, stems, and roots are only found in vascular plants

• Roots: Absorb water and minerals, anchor the plant.

Shift in Life Cycle Dominance

• Plants shifted from gametophyte-dominated (bryophytes) to sporophyte-dominated (vascular plants).

  • Flowering plants have large, complex sporophytes; gametophytes form inside flowers and consist of few cells.

  • Spores are more likely to survive than gametes, so increased spore production provides a greater advantage

Spores, Pollen, and Seeds

• Bryophytes and seedless plants release spores.

• Seed-bearing vascular plants (Gymnosperms and Angiosperms) release pollen grains and seeds.

  • Pollen grain: Walled, immature gametophyte that gives rise to sperm.

  • Seed: Embryo sporophyte and nutritive tissue inside waterproof coat.

  • Angiosperms disperse seeds inside a fruit.

Bryophytes

• Nonvascular plants, don't produce seeds, have swimming sperm (require a moist habitat)

• Include liverworts, hornworts, and mosses.

• Gametophyte-dominated life cycle.

• Lack true vascular tissue reinforced by lignin.

Seedless Vascular Plants

• Include Ferns, club mosses, spike mosses, whisk ferms

• Don't produce seeds, have vascular tissue (contain xylem and phloem), and have swimming sperm (require a moist habitat)

• Oldest vascular plant lineages.

• Flagellated sperm that swim to eggs; disperse by releasing spores.

• Sporophyte with lignified vascular tissue (xylem and phloem) dominates life cycle.

Ferns

• Most diverse seedless vascular plants.

• Sporophytes have leaves and roots that grow from rhizomes.

• Spores dispersed from clusters of sporangia (sori) on lower surfaces of frond leaves.

• Many live as epiphytes attached to another plant

• Fronds-are the leaves of the fern plant

Gymnosperms

• Type of seed plant, vascular (contains xylem and phloem), produces pollen and seeds.

• Seeds are in cones or totally exposed.

• Include conifers (pines), cycads, ginkgos, and gnetophytes.

Angiosperms

• Type of seed plant, vascular (contain xylem and phloem), produces pollen and seeds, also produces flowers and fruits.

• 95% of all living plant species are angiosperms.

• Flower: Specialized reproductive shoot consisting of modified leaves arranged in concentric whorls.

Selective Breeding in Plants

• Humans have long used selective breeding in plants to generate food products.

• The cornerstones of our food supply—corn, sweet potatoes, rice, and wheat (to name just a few)—are the result of long-term human manipulation of the life cycle of these plants.

Why Modify Plants?

• Improve fruit modification.

• Increase crop production.

• Add nutrients to our crops.

Risks of Modifying Plants

• Accidently producing "super-weeds".

• Negative health concerns like allergic reactions.

• Impact on non-pest species like butterflies.

Future of Plant Modification

• Developing plants that are heat and drought resistant.

• Developing fish and farm animals that can grow faster and contain more nutrients.