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Text for UF/IFAS/Plant Pathology “Genetic Engineering and Biotechnology”
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Slide Text: The text below is supplementary to what is presented on the slide itself
1
These are the four points that will be discussed in this presentation.
2
The definition of “biotechnology” may depend on who you ask. This is the definition
of biotechnology from the Convention on Biological Diversity, as stated on their
website. The convention is an international legal instrument supported by the United
Nations Environment Program (UNEP). The beginnings can be traced back to an “Ad
Hoc Working Group of Experts on Biological Diversity meeting in November 1988 to
explore the need for an international convention on biological diversity.”
3
Using this internationally recognized definition of “biotechnology”, one can see that
biotechnology is not new. But, our biotechnology techniques have progressed over
time from simply growing plant from seed obtained in the wild to precision breeding
using genome editing.
4
These are examples of current uses of biotechnology.
5
Nine different fruits and vegetables are shown in this slide. Do you know which ones
are genetically modified organism? How do you define a “genetically modified
organism”? We’ll see this slide again at the end of this presentation.
6
To plant pathologists, “genetic engineering” is very well known as it has been
happening naturally for centuries. The soil bacterium Agrobacterium tumefaciens is a
natural genetic engineer. The way it infects the plant and causes symptoms is by
inserting some of its DNA into the host plant DNA, and then forcing the plant to over
produce plant cells to form a gall or tumor. This slide illustrates the bacterial cell and
the plant cell. Note that the bacterial cell contains a plasmid, which is a small DNA
molecule physically separated from the chromosomal DNA in the cell.
7
This slide illustrates the first four steps in the infection of the plant and the preparation of the
plant cell to receive the T-DNA from the bacterial cell.
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It takes a few more steps before the T-DNA is integrated into the plant cell’s DNA.
Once that occurs, T-DNA genes will force the plant to produce special amino acids to
feed the bacterium.
9
This explains the next steps in the formation of galls (or tumors). Again,
Agrobacterium tumefaciens has been doing this without human intervention for
centuries.
Text for Plant Pathology PowerPoint “Genetic Engineering and Biotechnology”, Page 1
10
Beginning in the 1970s and 1980s, scientists began using Agrobacterium tumefaciens
to move genes from one organism into plants. This was the beginning of humans
genetically engineering plants. And new tools have followed, as listed here.
11
Scientists inserted a gene of interest from one organism into the T-DNA of
Agrobacterium tumefaciens. Then, the targeted plant was “infected” with this
transformed A. tumefaciens strain, which transferred the “gene of interest” into the
plant’s DNA when the bacterium transferred its T-DNA.
12
One of the first genes used was the firefly luciferase gene. When the tobacco plant
with this gene was sprayed with the chemical luciferin, the plant temporarily glowed.
This was a model system to demonstrate what could be done.
13
The next system developed to move genes into plants was the gene gun or biolistic
particle delivery system. The papaya industry in Hawaii was saved using this
technique. This is an excellent story demonstrating how perceptions can change
when everyone works together to solve a problem. The links are to a 5 ½ minute
video and an article on the papaya ring spot virus and its management with this plant
modification technique.
14
This is a long-winded explanation about gene silencing and how this known
phenomenon was used to control the papaya ring spot virus. Essentially, the DNA
inserted with the gene gun prevents the virus from replicating in the plant – no viral
replication, no disease!
15
A third technique used to insert new DNA into a plant is via protoplast fusion and
somatic fusion.
16
The newest technique is genome editing using CRISPR. It is somewhat similar to
“gene silencing”. Instead of stopping the production of a protein or virus, the “guide
RNA” cuts the offending DNA to disable or knock out a gene, without changing the
genome. However, if desired, the scientist can then insert a new piece of DNA at that
point, which would change the plant’s genome.
17
The system occurs naturally in bacteria as a defense mechanism. Scientists are not
trying to introduce it into other organisms, including plants.
18
Discussing Genetically Modified Organisms (GMOs) can be quite contentious. Finding
neutral information can be difficult. While this website, GMOAnswers.com, is
supported by agribusiness companies and farm organizations, the independent
experts who answer consumer questions are not paid by GMO Answers to answer
Text for Plant Pathology PowerPoint “Genetic Engineering and Biotechnology”, Page 2
questions. Experts donate their time to answer questions in their area of expertise for
the website. Some of these experts are with the University of Florida – IFAS.
19
GMO Answers.com has a very good PowerPoint that you can download free. This
slide and the next four are from that PowerPoint.
20
This slide illustrates how humans have modified plants to obtain plants that are edible
and productive. If these photos weren’t labeled, would you have recognized them as
“food” you eat today?
21
This slide illustrates methods of plant seed improvement over the centuries. Are you
paying attention? You will need this information for the quiz later!
Selective Breeding: The “traditional” method of obtaining new crops and new traits
within crops.
Interspecies Crosses: Breeding and tissue culture techniques that permit genetic
exchange between plants that do not cross naturally.
Mutagenesis: Using chemical or radiation on seeds to change DNA and occasionally
induce a favorable trait.
Transgenesis (GMO): Adding a specific, well-characterized gene to a plant to obtain a
specific trait.
22
GMO misconceptions that one finds in the news and various places on the internet.
And, none of them are true!
23
Three different agencies are involved in the regulation of GMO crops.
24
In May 2016, the National Academy of Science released a report on Genetically
Engineered Crops. The summary of the report is FREE and available at the site
indicated on the slide. It is also in the Plant Pathology Workshop Manual. Bottom
line: There is no evidence that genetically engineered crops are harmful to humans or
the environment, as compared to conventionally bred crops.
25
In 2015, almost 180 million hectares of genetically engineered crops were planted
globally. Most of the crops were herbicide-resistant varieties or insect-resistant
varieties. It has been much more difficult to develop disease-resistant crops.
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This slide illustrates the genetically-engineered crops and where they were grown.
27
This is the list of genetically-engineered crops grown in the U.S. and the traits that
were modified.
28
More resources for discussion on genetically modified crops. The first one is truly
superb and could be easily used in the classroom. Transcripts are available, so
Text for Plant Pathology PowerPoint “Genetic Engineering and Biotechnology”, Page 3
students could “debate” the issue. The last resource is an UF/IFAS Extension
document regarding genetically-modified tomatoes and why they are NOT being
planted in Florida.
29
Now, back to our quiz. Pick the genetically modified organism (crop).
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Only three of the nine vegetables or fruits shown in the slide can be labeled as
transgenic or genetically modified organism.
Rio Red Grapefruit: Grapefruit itself is a natural hybrid between sweet orange and
pomelo, first observed in the Caribbean in 1700s. Rio Red was developed by mutating
bud wood with thermal neutrons.
Tangelo: Interspecific cross between grapefruit and tangerine.
Squash: GMO;, Agrobacterium-mediated transformation in which the transfer-DNA
(T-DNA) contained the coat protein genes from the targeted virus.
Tomato: Selective breeding program only at this point in time.
Eggplant: GMO; Agrobacterium-mediated transformation with Bacillus thuringiensis
protein gene inserted to obtain resistance to a fruit and stem boring insect. The first
introduction was in Bangladesh
Japanese Pear: The variety “Golden Nijisseiki” was obtained by gamma radiation of the
leading variety “Nijisseiki” to obtain resistance to black spot disease.
Green Bean: Selective breeding program only at this point in time.
Papaya: GMO; The Hawaiian cultivar “Rainbow” was obtained with the gene gun.
RNA interference defends the fruit against the papaya ringspot virus.
Pluots: Interspecific cross between apricot and plum.
Text for Plant Pathology PowerPoint “Genetic Engineering and Biotechnology”, Page 4