Transcript VI. Genetic Engineering or Recombinant DNA Technology

Chapter 14
Plant Biotechnology
I. Introduction
A. Shrubs that "Glow in the Dark"
B. Traditional and Modern Biotechnology
II. Traditional Vegetative Propagation
A. Introduction
1. Grafting Defined
• the permanent union of parts of two plants
2. Ancient practices
a. Chinese practiced grafting by 1000 B.C.
b. Theophrastus discussed grafting in his book, Causes of
Plants
B. Stem Cuttings
1. Cuttings defined
• pieces of a plant that are induced to produce roots and are
then planted to grow on their own
2. Example of navel oranges. First mutation originated in
Brazil 1820. In 1873 it was shipped to Washington DC
then to Riverside, California
3. Procedures
C. Leaf Cuttings
• examples; African violets, peperomias, begonias
D. Root Cuttings
E. Layering
1. Tip layering
a. Tips of stem (canes) in blackberries and boysenberries
are covered with a mound of soil
b. Roots and shoots form on the buried portion
c. New plants can be separated from parent stems
2. Air layering
a. Wounded stem is wrapped in damp sphagnum moss and
covered with plastic film
b. Adventitious roots develop from injured areas on stem
c. Cut stem below root growth and plant in soil
F. Propagation from Specialized Stems and Roots
1. Rhizomes, tubes, and corms
• divided and grow into new plant
2. Bulbs
• hyacinth, grape hyacinth induced to form bulblets by
wounding
3. Fleshy storage roots
• sweet potatoes, dahlias
III. Grafting
A. Grafting Process
• insertion of a short stem portion, the scion, into another
stem, the stock, containing a root system
B. Grafted Part Must Be Related
• can not graft maple wood to an apple tree
IV. Traditional Plant Breeding
A. The Green Revolution
1. Defined
• development of high yielding strains of wheat and other
grains
2. Norman Borlaug
a. "Father of the Green Revolution"
b. Awarded Nobel Prize in 1970 for developing new strains
of wheat in Mexico
3. Drawbacks
a. Plentiful water supply required (i.e., irrigation water)
b. Extensive applications of fertilizer required
B. Hybridization
1. Crossing of different varieties yield F1 seed with hybrid
vigor
2. Corn grown in North America comes from F1 hybrid
seed
3. Bread wheat hybrids
C. Polyploidy
1. Defined
• flowering plants that have more than two sets of
chromosomes
2. Types
a. Alloploidy
• hybridization followed by a doubling of the
chromosome number
b. Autoploidy
• chromosomes doubled when pairs of chromosomes fail
to separate during mitosis or meiosis
3. Artificially creating polyploids
a. Treating seeds with colchicine
• interferes with spindle formation during mitosis
b. Wounding and callus formation e.g. tomato
c. Application of heat to seeds e.g. corn
D. Mutations
1. Defined
• involves a change in a gene or chromosome
2. Induced mutations
a. Radiation
b. Chemicals
3. Usefulness of mutations
• some induced mutations have yielded better strains of
Penicillium mold
V. Tissue Culture and Mericloning
A. Tissue Culture
1. Defined
• a mass of callus tissue growing on an artificial medium
2. Techniques
a. Isolate plant tissues from meristems or pith
b. Place in sterile growth medium
c. Rapid multiplication of cells occurs
d. Tissue may differentiate into roots, shoots, or plant
embryos
3. Crop improvement through tissue culture
a. Can select desirable traits from large population of cells
b. Can subject cells to stresses such as herbicides, heat, cold,
etc., then select the survivors that are resistant to applied
stress
B. Shoot Meristem Culture (Mericloning)
1. Defined
• growth of a new plant by removing the apical meristem
and placing it on sterile growth medium
2. Advantages
• tissue growth can be subdivided and cultured to yield
many identical plants
3. Examples
• orchids
C. Artificial Seeds
1. Genetically identical embryos are mass-produced through
tissue culture
2. Embryos packaged with a food supply, hormones, and a
biodegradable protective coat
3. Identical plants produced which may lessen the expense of
harvesting the crop
D. Protoplast Fusion
1. Cell walls are digested which leaves naked protoplasts
2. Protoplasts minus their walls can then fuse or hybridize
3. Hybrid cells can be selected for and cultured
4. Somatic hybrids are the result of a fusion from two different
protoplasts
E. Clonal Variants
1. Cells with slightly different characteristics are frequently
found in cultures
2. Variant cells are grown into desirable plants in a shorter
time than normal plant breeding techniques would permit
VI. Genetic Engineering or Recombinant DNA Technology
A. Process of Genetic Engineering
1. Remove a gene from its normal location
2. Insert gene into a circular form of bacterial DNA called
plasmid DNA
3. Plasmid DNA carrying gene is transferred into cells of
another species
B. Isolation of Plasmid DNA
C. Restriction Enzymes
1. From bacteria
2. Break a circular plasmid at a specific nucleotide sequence
D. Repair Enzymes
1. Called DNA ligases
2. Links two fragments of DNA together
E. Instruments that Facilitate Gene Cloning
1. Protein sequencer
• can determine the amino acid sequence of a protein
2. Gene synthesizer
• can synthesize specific nucleotide sequences of a gene
F. Polymerase Chain Reaction (PCR) Technology
G. Cell Bombardment and Electroporation
1. Cell Bombardment
a. Shoot DNA-coated particles into plant cells
b. 2% of bombarded cells take up foreign DNA
2. Electroporation
a. Cells placed in an electrical field
b. Cell wall becomes permeable to admit foreign DNA
H. Other Applications of Genetic Engineering
1. Early Experiments
a. Transgenic mice (1980)
• foreign gene introduced into fertilized mouse eggs
b. Transgenic plants
• gene from French bean transferred to cell of
sunflower plant, called "sunbean"
2. Later Developments
a. Herpes virus vaccine
b. Hepatitis B vaccine produced in plants
c. Genetically engineered pesticide
d. Genetically altered canola
e. Insect resistant seeds
f. White blood cells with "tracking" gene injected into
terminal cancer patients
g. Sun lotion to protect against cancer-causing radiation
h. Flavr Savr tomato (Calgene, Inc., Davis, California)
• first engineered food product to reach market (1994)
i. Rust resistance beans
j. Antifreeze gene from Antarctic fish
I. A Few Pros and Cons of Genetic Engineering
1. Fear of release in the environment of genetically altered
species
2. Promise of genetically altered plants that require less
herbicides
3. Promise of improved human quality of life with
genetically engineered products