Human Manipulation of Plants - Textbook

Human Manipulation of Plants OUTLINE 1- Artificial vs. Natural Selection. 2- Traditional Methods of Plant Manipulation. 3- Plant Evolution & Speciation. 4- Beyond Traditional Methods. 2  Introduction Originally modern humans were hunters- gathers....

Human Manipulation of Plants OUTLINE 1- Artificial vs. Natural Selection. 2- Traditional Methods of Plant Manipulation. 3- Plant Evolution & Speciation. 4- Beyond Traditional Methods. 2  Introduction Originally modern humans were hunters- gathers. 9000 yrs ago, moved to agriculture & depended on plants. Humans started cultivating plants, by unconsciously selecting specific characteristics. Now, humans use biotechnology to produce genetically modified organisms. ( GMO) 3 Wheat Fruit Stalk Wild type: Shattering Cultivated: Non- Shatterin 4  Sex- or Not- in Plants  Flowering plants reproduce sexually.  Sexual reproduction provides variability in which selection acts.  Variability is achieved by: 1- Shuffling of genes. 2- Mutations that cause changes to DNA sequences.  Nature selects the Fittest. Table 3.1  Fittest, refers to the individual who produces the highest # of fertile offsprings.  Artificial selection is when man selects desirable traits. 5 6  1-Selections in Angiosperms Artificial Selection vs. Natural Selection Change. make up Change in genetic make up caused by natu in genetic caused Major force of evolution in wild plts. by man Humans selected plts: Changes in gene frequencies are caused 1- high yields ( more by biotic & abiotic seeds, less roots). factors: 2- inc. nutritional value. 1- Living agents (predation, 3- improved competition, disease) appearance. 2- Nonliving factors (soil type Altitude, rain, wind). 4- pest resistance. 7 A plant species that generally have smooth leaves has undergone a mutation and some leaves are hairy Some plants within a population exhibit variation in leaf structure. Deer prefer a diet of smooth leaves over hairy leaves. Plants with hairy leaves reproduce more than other plants in the population. Generations later, most plants within the population have hairy leaves, as smooth leaves are selected against. 2-Traditional Methods of Plant Manipulation 1- Enhance inbreeding 2- Asexual propagation of plants. 9  1- Inbreeding vs. Outcrossing Inbreeding (self pollination or self fertilization). Flowering plants are bisexual. Fusion of gametes within a fl. (perfect) or fusion of gametes of separate but genetically similar plts ( imperfect). Provides high yields of seeds but low variability. Common in annual herbs & weeds. 10 Inbreeding occurs, if fl. is Self- compatible 1- Proximity. 2- Gametes must be shed at the same time. 11  Angiosperm prefer outcrossing.  Outcrossing fusion of gametes from genetically different individuals which leads to genetic diversity.  A larger number of offsprings survive when environmental conditions change.  Strategies used by angiosperms to achieve outcrossing: 1- Temporal separation 2- Spatial separation. 3- Genetic incompatibility ( most common) 12 ♀ first ♂ first Oats Fuchsia 1- Temporal Separation 13 Humans, select mutation that facilitate self- pollination Outcrossing Self-pollinating 2- Spatial Separation 14 3- Genetic incompatibility 15  Why do farmers prefer inbreeding? 1- Rapid production of homozygous individuals, genetically identical Uniform stands, in terms of quality Mature together Used as a parent 2- Inbred lines produce hybrid seeds (large in size & larger seed crop) Hybrid vigor or heterosis 3- Advantageous in fields with a single crop (wheat, grapes, peas ). Self pollinating, no need for pollinators. 16 17 2-Asexual Reproduction, Clone = identical replica 1- Production of seeds from diploid maternal cells. Seeds are genetically identical to mother. Agamosper Vulnerable to fungal attacks. my 2- Vegetative propagation, pieces of leaves, stems, rhizome, etc. 1- grow & mature faster. 2- less vulnerable to fungal attacks than seedlings. 1 & 2 ensure crop uniformity even more than inbreeding. 3- Grafting, artificial method of asexual reproduction. 18  Scion = carries the desirable character. Ex. fruit size, flavor, appearance Rootstock= several years old, cold tolerant, disease resistant Splice graft Bud graft Leaf abscission ndicates success Cleft Both scions are 19 assessed, best is left  Few advantages of grafting: 1- Get more than one harvest. 2- Save a lot of space. 3 varieties on one rootstock. 3- Attract different pollinators. he scion & rootstock should belong to the same family 20  3-Speciation: Plant Evolution Allopatric vs. Sympatric A population that is Instantaneous speciation, geographically split into 2, no geographical separatio the two separate but populations evolve due to polyploidy Main reason behind evolution in substantial differences domesticated plants. It can occur b leading to speciation. chance alone & it can be induced b Population a becomes chemicals different than population b. different geo conditions 21 Polyploidy = more than two sets of chromosomes (triploid, tetraploid, hexaploids etc.. ). Results: large plants, large fruits, big seed crop. Autopolyploidy 22 Two types of Polyploidy: Allopolyploid vs. Autopolyploid Polyploid of hybrid Ind. has more than 2 sets ch. from origin. same spp. 2 sets of ch from two different spp. get doubled 23  Consider two genetically different individua Allopolyploid Large plant that produces large fruits & 2n=10 a big seed crop. Ex: Triticale 24  ticale= human made cereal (2n=42) ticale= Wheat (4n=28) X Rye (2n=14) eat gives high yield e= hardiness 25 Autopolyploidy, Meiotic error. It occurs when an individual has more than two sets of chromosome derived from one species. 26 27 Early Experiments in Altering Plant Genes An entirely new allele is produced in nature is by a mutation.  MUTATION in a gene New protein. 20th. C. Agronomists used Mutagens = X ray or chemicals that induce mutations in sex cells, hoping for desirable changes in the plant.  All trials failed to obtain useful new cultivars. 28  Agronomist Dream: 1- Plants that produce their own pesticides which is nontoxic to humans. 2- Plants that are resistant to herbicides. 3- Plants that mature without a mushy flesh. 4- Plants that can produce medicine for human. 29 How can we introduce a trait which does not exist in the species, or was lost with time? Beyond Traditional Methods: Biotechnology, use of living organism to provide products for humanity. Two techniques: 1- Protoplast manipulation. Plant cells are less programmed for a specific functio 2- Genetic engineering. 30 1- Protoplast manipulation 1- adding enzymes to dissolve plant cell walls= protoplast 3- Fusion of 2 2- cells are proplasts is assayed for a done by PEG to desirable trait, Ex. produce a resistance to hybrid, grown herbicide on proper media 4- Callus, Undifferentiate tissue that can propagate on its own 5- New hybrid plant31 32 Why Generic Engineering? GMO? 1- A species might not have the character we desire, so we have to insert the gene. 2- Many major crops propagate asexually. Ex. Banana, potatoes. Breeding involves a sperm fusing with an egg. 3- Breeding programs will work within the same species or closely related species. Ex. Insect repellent gene in milkweed can not be inserted in tomatoes using traditional methods. 33 - Genetic Engineering, alter the genetic make up of an individual. Bacterial plasmid acts as a carrier Insert a DNA Fragment Restriction Endonuclease containing a (EcoRI) recognizes GAATT gene of interest. 34  = Tumor inducing plasmid that carries T-DNA which causes crown gall disease Agrobacterium tumefaciens cell Acts as a vector Reporter Construct= is inserted in the TDNA, contains all necessary components for successful integration and expression. 1. Promotor= initiates reading of the gene. 2. Reporter, marker gene that indicates the presence of the 35 gene.  Ballistic method Disable the T-DNA Construct Recombinant Ti plasmid What are few challenges? -Hard to find the specific gene that carries the trait mRNA has introns, change mature mRNA o cDNA by reverse transcription. -Desired character is controlled by many genes & the genes are on diff. chromosomes. - Only for dicots 36 Following Ballistic method, cells are spread on a nutrient medium with a chemical that gives a color indicating which of the cells have incorporated the inserted gene. 37 Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 38  Biotechnology products, 1990:  Important uses of Biopharming human serum albumin (potato & tobacco )  Tobacco plant producing insulin.  Corn, soya & potato producing antibodies. Plants resistant to herbicides= Glyophosate kills weeds. Bt crops= Plants produce their own pesticide that are nontoxic to humans. Plants resistant to frost 39