1. Biotechnology in
Agriculture
Chapter 11

2. Learning Outcomes
Describe the role of meristematic tissue in propagating plants by various asexual methods
Outline and discuss the process of plant tissue culture, including the importance of the different hormones involved, and identify the advantages and challenges of plant tissue culture
Give specific examples of agricultural and horticultural biotechnology applications, 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 and explain the selection processes for identifying transformed plant cells

3. Asexual Plant Propagation
11.1 Cloning Plants
Using breeding techniques, a plant biotechnologist can produce variety in the offspring of selected parental plants.
Asexual Plant Propagation
Identical offspring are produced by a single parent.
Methods of Asexual Plant Propagation

4. Vocabulary
Arabidopsis thaliana – an herbaceous plant, related to radishes, that serves as 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 are produced 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 soil’s 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 tissue culture has all of the required nutrients, chemicals, and hormones to promote cell division and specialization

5. 11.1 Review Questions
Which of the following are examples of asexual plant propagation: PTC, selective breeding, stem cuttings, leaf cuttings, or runner?
How is length or width added to a plant?
Leaf or stem cuttings must include a least some of what kind of tissue to form new roots?

6. 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

7. 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 material
The medium and medium ingredients
The preparation of plant samples, medium, and equipment (sterility and temperatures, etc.)

8. 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 tissue culture 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

9. 11.2 Review Questions What is another name for plant hormones?
Auxin is responsible for what kind of plant growth regulation? Cytokinin is responsible for what kind of plant growth regulation?
How can a plant tissue culturist know that an explant is beginning to respond to the hormones in the PTC media?

10. 11.3 New Applications of Biotech in Agriculture and Horticulture
Selective breeding of livestock and plant crops has been practiced for centuries.
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.

11. 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

12. 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.

13. 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. thuringienses or BT) – the bacterium from which the Bt gene was originally isolated; the Bt gene codes for the production of a compound that is toxic to insects
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)

14. 11.3 Review Questions
What is it called when very closely related animals are bred? Why is it discouraged?
Name two advantages of growing plants hydroponically.
How are PMPs related to genetically engineered organisms?

15. 11.4 Isolating DNA from Plant Cells
The DNA used in plant biotechnology applications may be genomic 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 kits
Buffers for plasmid isolation

16. Vocabulary Genomic DNA (gDNA) – the chromosomal DNA of a cell
Agrobacterium tumefaciens (A. tumefaciens) – a bacterium that transfers the “Ti plasmid” to certain plant species, resulting in a plant disease called crown gall; used in plant genetic engineering
Ti plasmid – a plasmid found in Agrobacterium tumefaciens that is used to carry genes into plants, with the goal that the recipient plants will gain new phenotypes

17. 11.4 Review Questions Which is larger, gDNA or pDNA, and by how much?
Plant DNA is difficult to get out of plant cells. List a few “tricks” used by technicians to isolate plant DNA.
Why is the bacteruim, A. tumefaciens, of interest to biotechnologists?
Why is Ti plasmid of interest to biotechnicians?

18. 11.5 Plant Genetic Engineering
Using A. tumefaciens to Genetically Engineer Plants
Transforming Agrobacterium. Before A. tumefaciens can be used to transform a plant, its Ti plasmid must be transformed with the gene(s) of interest.

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

20. Arabidopsis thaliana, a Model Organism for Plant Genetic Engineering
Arabidopsis thaliana has been the target of plant genetic engineering studies.

21. Vocabulary
Transgenic plants – plants that contain genes from another species; also called genetically engineered or genetically modified plants
NPT II (neomycin phosphotransferase) gene – a gene that codes for the production of the enzyme, neomycin phosphotransferase, which gives a cell resistance to the antibiotic kanamycin
GUS gene – a gene that codes for an enzyme called beta-glucuronidase, an enzyme that breaks down the carbohydrate, X-Gluc, into a blue product

22. 11.5 Review Questions
What is the name of the naturally occurring bacterium and the plasmid that can infect plants and transfer DNA molecules?
Name at least two selection genes that are used to confirm that Ti plasmid transformation has occurred.
How does GUS act as a selection gene?
Why are so many plant genetic-engineering experiments conducted with Aradibopsis, even though it has little, if any, economic value?

23. Questions and Comments?