Biotech Chapter 11

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Biotechnology inAgriculture

Chapter 11


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Learning Outcomes

Describe the role of meristematic tissue in propagating plants byvarious asexual methods

Outline and discuss the process of plant tissue culture, including theimportance of the different hormones involved, and identify theadvantages and challenges of plant tissue culture

Give specific examples of agricultural and horticultural biotechnologyapplications, including genetically modified organism (GMO) crops,hydroponics, and plant-made pharmaceuticals

Explain how genomic and plasmid DNA can be isolated from cells,including the additional steps required for plant cells

Summarize the methods used to produce transgenic plants andexplain the selection processes for identifying transformed plant cells


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11.1 Cloning Plants

Using breeding techniques, a plant biotechnologist can produce varietyin the offspring of selected parental plants.

Asexual Plant Propagation

Identical offspring are produced by a single parent.

Methods of Asexual Plant Propagation


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Vocabulary

Arabidopsis thaliana an herbaceous plant, related to radishes, that servesas a model organism for many plant genetic engineering studies

Crossbreeding pollination between plants of different phenotypes, or

varieties

Asexual plant propagation a process by which identical offspring areproduced by a single parent; methods include the cutting of leaves and stems,and plant tissue culture, etc.

Runners long, vine-like stems that grow along the soils surface

Plant tissue culture (PTC) the process of growing small pieces of plants

into small plantlets in or on sterile plant tissue culture medium; plant tissueculture has all of the required nutrients, chemicals, and hormones to promotecell division and specialization


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11.1 Review Questions

1. Which of the following are examples of asexual plant propagation:PTC, selective breeding, stem cuttings, leaf cuttings, or runner?

2. How is length or width added to a plant?

3. Leaf or stem cuttings must include a least some of what kind oftissue to form new roots?


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11.2 Cloning by Plant Tissue Culture

In PTC a few cells are grown in sterile media, with sugar,vitamins, and correct hormones.

Hormone Function in Plants

Plant Growth Regulators

Auxin

Cytokinin


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Starting a Tissue Culture

Hormones, agar, nutrients

Advantages of Plant Tissue Culture Propagation

More plantlets are produced.Produces clones of the parent with no variations.Some plants do not propagate will other ways.

Factors to Consider in Plant Tissue Culture Propagation

The species and variety of plant materialThe medium and medium ingredientsThe preparation of plant samples, medium, and equipment (sterility andtemperatures, etc.)


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Vocabulary

Plant growth regulators another name for plant hormones

Auxin a plant hormone produced primarily in shoot tips that regulates cell

elongation and leaf development Cytokinin a class of hormones that regulates plant cell division

Explants sections or pieces of a plant that are grown in or on sterile plant tissueculture media

Ethylene a plant hormone that regulates fruit ripening and leaf development

Abscisic acid a plant hormone that regulates bud development and seed dormancy

Phytochrome a pigment that acts like a hormone to control flowering


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1. What is another name for plant hormones?

2. Auxin is responsible for what kind of plant growth regulation?Cytokinin is responsible for what kind of plant growth regulation?

3. How can a plant tissue culturist know that an explant is beginningto respond to the hormones in the PTC media?


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11.3 New Applications of Biotech in Agriculture and Horticulture

Selective breeding of livestock and plant crops has been practiced forcenturies.

New techniques are now being applied.

Genetic Testing and Gene Transfer

With DNA fingerprinting, breeders can test parent animals and plants for

several beneficial genes and recognize several undesirable genes.


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Benefits of Selective Breeding and Propagation

Animals:

Improved nutritional value Fewer feed additives Increased growth rate

Plants: Resistant to selected viruses Higher nutritional content Less fertilizer or herbicide Less environmental impact from run-off pollution


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Hydroponics: An Alternative Plant Growing Method

Soil-less, water-based medium in which to grow plants

Plant-Made (Plant-Based) Pharmaceuticals

Since the 1970s, human proteins have been made in bacterial,

fungal, or mammalian cell cultures.


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Vocabulary

Agriculture the practice of growing and harvesting animal or plant crops for food, fuel,fibers, or other useful products

Horticulture the practice of growing plants for ornamental purposes

Inbreeding the breeding of closely related organisms

Bacillus thuringiensis (B. thuringiensesor BT) the bacterium from which the Bt genewas originally isolated; the Bt gene codes for the production of a compound that is toxic toinsects

Hydroponics the practice of growing plants in a soil-less, water-based medium

Plant-based pharmaceutical (PBP) a human pharmaceutical produced in plants; also

called plant-made pharmaceutical (PMP)


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1. What is it called when very closely related animals are bred?

Why is it discouraged?2. Name two advantages of growing plants hydroponically.

3. How are PMPs related to genetically engineered organisms?


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11.4 Isolating DNA from Plant Cells

The DNA used in plant biotechnology applications may begenomic DNA (gDNA) or plasmid DNA (pDNA).

Isolating Genomic DNA

Cells must be burst open.Proteins are precipitated and removed from solution.RNA is destroyed.Remaining DNA is precipitated.

Isolating Plasmid DNA

Plasmid isolation kitsBuffers for plasmid isolation


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Vocabulary

Genomic DNA (gDNA) the chromosomal DNA of a cell

Agrobacterium tumefaciens (A. tumefaciens)a bacterium that transfers the Tiplasmid to certain plant species, resulting in a plant disease called crown gall; used inplant genetic engineering

Ti plasmid a plasmid found inAgrobacterium tumefaciensthat is used to carry genesinto plants, with the goal that the recipient plants will gain new phenotypes


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1. Which is larger, gDNA or pDNA, and by how much?

2. Plant DNA is difficult to get out of plant cells. List a few tricks used

by technicians to isolate plant DNA.

3. Why is the bacteruim,A. tumefaciens, of interest to biotechnologists?

4. Why is Ti plasmid of interest to biotechnicians?


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11.5 Plant Genetic Engineering

UsingA. tumefacienstoGenetically Engineer Plants

TransformingAgrobacterium.BeforeA. tumefacienscan be usedto transform a plant, its Ti plasmidmust be transformed with thegene(s) of interest.


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Ti Plasmid. The Ti plasmid has two selection genes on it, NPT II and beta-D-glucuronidase (GUS), so that when itgets into plant cells, the plasmid transfer can be recognized. Cells receiving this plasmid will be able to survive onkanamycin-containing agar (from NPT II expression). They will also be able to convert a white carbohydrate in themedium to a blue color (due to GUS expression), which makes the entire colony blue, allowing the researcher toascertain successful DNA transfer.


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Arabidopsis thaliana, a Model Organism for Plant Genetic Engineering

Arabidopsis thalianahas been the target of plant genetic engineeringstudies.


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Vocabulary

Transgenic plants plants that contain genes from another species; also calledgenetically engineered or genetically modified plants

NPT II (neomycin phosphotransferase) gene a gene that codes for theproduction of the enzyme, neomycin phosphotransferase, which gives a cellresistance to the antibiotic kanamycin

GUS gene a gene that codes for an enzyme called beta-glucuronidase, anenzyme that breaks down the carbohydrate, X-Gluc, into a blue product


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1. What is the name of the naturally occurring bacterium and theplasmid that can infect plants and transfer DNA molecules?

2. Name at least two selection genes that are used to confirm thatTi plasmid transformation has occurred.

3. How does GUS act as a selection gene?

4. Why are so many plant genetic-engineering experiments

conducted with Aradibopsis, even though it has little, if any,economic value?


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Questions and Comments?

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Biotech Chapter 11