The Science of Transgenics
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The Science of Transgenics The Sociological, Economic, and Ethical Impact of Transgenic Organisms Workshop Fargo, ND February 21, 2003 NDSU Phil McClean Department of Plant Science North Dakota State University Extension Transgenics are a Biotechnology Product How about some definitions Biotechnology - General Definition The application of technology to improve a biological organism NDSU Biotechnology - Detailed Definition The application of the technology to improve the biological function of an organism by adding genes from another organisms Extension What About the Term Genetic Engineering? Genetic engineering is the basic tool set of biotechnology Genetic engineering involves: Isolating genes Modifying genes so they function better Preparing genes to be inserted into a new species Developing transgenes NDSU Extension What is a transgenic? Concept Based on the Term Transgene Transgene – the genetically engineered gene added to a species Ex. – modified EPSP synthase gene (encodes a protein that functions even when plant is treated with Roundup) Transgenic – an organism containing a transgene introduced by technological (not breeding) methods NDSU Ex. – Roundup Ready Crops Extension Why are transgenics important? We can develop organisms that express a “novel” trait not normally found in the species Extended shelf-life tomato (Flavr-Savr) Herbicide resistant soybean (Roundup Ready) NDSU Extension Agriculture Transgenics On the Market Insect resistant cotton – Bt toxin kills the cotton boll worm • transgene = Bt protein Source: USDA Insect resistant corn – Bt toxin kills the European corn borer • transgene = Bt protein Normal Transgenic NDSU Extension Herbicide resistant crops Now: soybean, corn, canola Coming: sugarbeet, lettuce, strawberry alfalfa, potato, wheat (2005?) • transgene = modified EPSP synthase or phosphinothricin-N-acetyltransferase Source: Monsanto Virus resistance - papya resistant to papaya ringspot virus • transgene = virus coat protein NDSU Extension Source: Chr. Hansen Biotech chymosin; the enzyme used to curdle milk products • transgene = genetically engineered enzyme bST; bovin somatotropin; used to increase milk production • transgene = genetically engineered enzyme Source: Rent Mother Nature NDSU Extension Some Ag Biotech Products Are Discontinued Why??? Poor Quality • FlavrSavr tomatoes (Calgene) Negative Consumer Response • Tomato paste (Zeneca) Negative Corporate Response • NewLeaf (Monsanto) NDSU Universal Negative Publicity • StarLink corn (Aventis) Extension Next Generation of Ag Biotech Products Golden Rice – increased Vitamin A content (but not without controversy) transgene = three pathway enzymes Sunflower – white mold resistance transgene = oxalate oxidase from wheat Source: Minnesota Microscopy Society NDSU Extension Turfgrass – herbicide resistance; slower growing (= reduced mowing) Bio Steel – spider silk expressed in goats; used to make soft-body bullet proof vests (Nexia) NDSU Extension Biotechnology is Not Just on the Farm Disease Treatment Diagnostics Environmental Cleanup Human Applications NDSU Extension Human Applications • Pharmaceutical products New solutions to old problems • Disease diagnosis Determine what disease you have or may get • Gene therapy Correcting disease by introducing a corrective gene NDSU Extension Biotechnology and Health Product Use Insulin Diabetes Interferon Cancer Interleukin Cancer Human growth hormone Dwarfism Neuroactive proteins Pain NDSU The genes for these proteins are: • Cloned • Inserted into bacteria • Product isolated using biofermentation Extension Environmental Applications Bioremediation - cleanup contaminated sites; uses microbes designed to degrade the pollution Indicator bacteria – contamination can be detected in the environment NDSU Extension Future Health-related Biotech Products Vaccines – herpes, hepatitis C, AIDS, malaria Tooth decay – engineered Streptococcus mutans, the bacteria that destroys enamel NDSU Extension Edible Vaccines Transgenic Plants Serving Human Health Needs • Works like any vaccine • A transgenic plant with a pathogen protein gene is developed • Potato, banana, and tomato are targets • Humans eat the plant • The body produces antibodies against pathogen protein • Humans are “immunized” against the pathogen • Examples: Diarrhea Hepatitis B Measles NDSU Extension A Popular Term We Need To Know GMOs - Genetically modified organisms • GMO - an organism that expresses traits that result from the introduction of foreign DNA • Originally a term equivalent to transgenic organism NDSU Extension The GMO Ruse Some claim any improved biological product is a GMO They feel this will • ease the publics fear • pave the way for product acceptance For example, some call plant varieties biotechnology products This is a false claim NDSU Extension Let’s Be Up Front • Biotechnology adds traits not available in the species Soybean does not have a gene to breakdown Roundup The gene comes from bacteria • Breeding Biotechnology Breeding only exchanges genes found in the species Breeding can transfer the transgene to other breeding materials BUT this does not make it a biotechnology procedure NDSU Extension Important Plant Improvement Methods Source: USDA • Breeding Crossing two individuals from the same species; produces a new, improved variety; not a biotechnology procedure • Transformation Adding a gene from another species; the essential biotechnology procedure to produce transgenics Source: USDA NDSU Extension Interspecific Cross Wheat Rye X Triticale New species, but NOT biotechnology products NDSU Extension Mutagenesis A useful procedure to produce a new trait But the normal gene is modified A transgene is not involved The product of mutagenesis is not a GMO NDSU Extension Mutagenesis Changes the DNA Sequence Mutagenesis Treatment Susceptible Normal Gene Resistant Mutant Gene ATTCGA ATTGGA NDSU Extension BASF Clearfield Products NDSU Herbicide resistance •imidazolinones Mutant AHAS enzyme •developed by mutagenesis Crops • Canola • Corn • Rice • Sunflower • Wheat A Major Marketing Advantage but lost when stacked with a transgene Extension The Roundup Ready Story • Glyphosate is a broad-spectrum herbicide • Active ingredient in Roundup herbicide • Kills all plants it come in contact with • Inhibits a key enzyme (EPSP synthase) in an amino acid pathway • Plants die because they lack the key amino acids • A resistant EPSP synthase gene allows crops to survive spraying NDSU Extension Roundup Sensitive Plants Shikimic acid + Phosphoenol pyruvate + Glyphosate Plant EPSP synthase X 3-Enolpyruvyl shikimic acid-5-phosphate (EPSP) Without amino acids, plant dies X X X NDSU Aromatic amino acids Extension Roundup Resistant Plants Shikimic acid + Phosphoenol pyruvate + Glyphosate Bacterial EPSP synthase RoundUp has no effect; enzyme is resistant to herbicide 3-enolpyruvyl shikimic acid-5-phosphate (EPSP) With amino acids, plant lives NDSU Aromatic amino acids Extension The Golden Rice Story • Vitamin A deficiency is a major health problem • Causes blindness • Influences severity of diarrhea, measles • >100 million children suffer from the problem • For many countries, the infrastructure doesn’t exist to deliver vitamin pills • Improved vitamin A content in widely consumed crops an attractive alternative NDSU Extension -Carotene Pathway Problem in Plants IPP Geranylgeranyl diphosphate Phytoene synthase Phytoene Problem: Rice lacks these enzymes Phytoene desaturase ξ-carotene desaturase Lycopene Lycopene-beta-cyclase -carotene (vitamin A precursor) NDSU Normal Vitamin A “Deficient” Rice Extension The Golden Rice Solution -Carotene Pathway Genes Added IPP Geranylgeranyl diphosphate Daffodil gene Phytoene synthase Phytoene Vitamin A Pathway is complete and functional Phytoene desaturase Single bacterial gene; performs both functions ξ-carotene desaturase Lycopene Daffodil gene -carotene (vitamin A precursor) NDSU Golden Rice Lycopene-beta-cyclase Extension Introducing the Gene or Developing Transgenics Steps 1. Create transformation cassette 2. Introduce and select for transformants NDSU Extension Transformation Cassettes Contains 1. Gene of interest • The coding region and its controlling elements 2. Selectable marker • Distinguishes transformed/untransformed plants 3. Insertion sequences • Aids Agrobacterium insertion NDSU Extension Transformation Steps Prepare tissue for transformation • Tissue must be capable of developing into normal plants • Leaf, germinating seed, immature embryos Introduce DNA • Agrobacterium or gene gun Culture plant tissue • Develop shoots • Root the shoots Field test the plants • Multiple sites, multiple years NDSU Extension Delivering the Gene to the Plant • Transformation cassettes are developed in the lab • They are then introduced into a plant • Two major delivery methods • Agrobacterium • Gene Gun NDSU Tissue culture required to generate transgenic plants Extension The Lab Steps NDSU Extension The Next Test Is The Field Herbicide Resistance Non-transgenics Transgenics NDSU Extension Final Test of the Transgenic Consumer Acceptance RoundUp Ready Corn After NDSU Before Extension
