4.6 Case study: Genetic engineering in combating viruses in agriculture

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From the course by Tel Aviv University

Understanding Plants - Part II: Fundamentals of Plant Biology

313 ratings

Tel Aviv University

Understanding Plants - Part II: Fundamentals of Plant Biology

313 ratings

This class is aimed at people interested in understanding the basic science of plant biology. In this four lecture series, we'll first learn about the structure-function of plants and of plant cells. Then we'll try to understand how plants grow and develop, making such complex structures as flowers. Once we know how plants grow and develop, we'll then delve into understanding photosynthesis - how plants take carbon dioxide from the air and water from soil, and turn this into oxygen for us to breathe and sugars for us to eat. In the last lecture we'll learn about the fascinating, important and controversial science behind genetic engineering in agriculture. If you haven't taken it already, you may also be interested in my other course - What A Plant Knows, which examines how plants see, smell, hear and feel their environment: https://www.coursera.org/learn/plantknows. In order to receive academic credit for this course you must successfully pass the academic exam on campus. For information on how to register for the academic exam – https://tauonline.tau.ac.il/registration Additionally, you can apply to certain degrees using the grades you received on the courses. Read more on this here – https://go.tau.ac.il/b.a/mooc-acceptance Teachers interested in teaching this course in their class rooms are invited to explore our Academic High school program here – https://tauonline.tau.ac.il/online-highschool

From the lesson

Plant genetic engineering

4.1 Introduction4:54

4.2 Cultivated foods and genetic changes5:50

4.3 Conventional breeding and genetic engineering methods3:35

4.4 Recombinant DNA technology8:17

4.5 Transgenic plants - proof of concept5:34

4.6 Case study: Genetic engineering in combating viruses in agriculture4:42

4.7 Examples of genetic engineering: Nutritional benefits3:29

4.8 Potential of genetic engineering: I Insect resistant plants3:56

4.9 Concerns about the use of genetic engineering in agriculture6:30

Meet the Instructors

Professor Daniel Chamovitz, Ph.D.
Dean, George S. Wise Faculty of Life Sciences
Director, Manna Center for Plant Biosciences

Now that we've seen how genetic engineering works,

how can this technology be used for the common good?

And when most of you think of genetic engineering or genetically

modified plants, you probably think of transgenic corn or soybeans or cotton.

And indeed these crops

make up the majority of transgenic crops grown around the world.

But I want to start with a lesser known example, but

one that has been on the market since 1998.

Papaya.

Why papaya?

We're going to talk about papaya because of a deadly viral disease of papaya

called, papaya ringspot disease.

This disease is caused of a virus, and

it has many morphological effects on the plant.

For example, these ringspots on the fruit itself.

But it also causes yellowing of the leaves,

molting of the leaves, dark green streaks.

In the end,

it severely effects the vigor of the trees and can even lead to tree death.

And of course, huge drops in yield.

This virus was found in the 1960s in Brazil.

And one of the ways that you could fight the virus was by transferring healthy

plants to a new area of the country,

a new agricultural area where the virus wasn't found.

So this was a known virus that had the potential to threaten papaya growers

worldwide.

And one of the main centers of papaya growth in the United States is in Hawaii.

Thus research was started in 1978 to find control measures for

the papaya ringspot virus.

And indeed though, in 1992, the virus was discovered in Puna,

which is the area where 95% percent of Hawaii's papaya was being grown.

And this virus completely devastated the papaya industry.

Such that, in 1992 there was about 53 million pounds

of papaya harvested, in 1998 this had dropped to only 26 million pounds.

Luckily, the Hawaiian papaya industry realized that there was a potential for

disaster and started research even before the virus started spreading in Puna.

A Hawaiian scientist named Dennis Consolves.

Who was then working at Cornell.

Worked with colleagues both in Cornell and at the University of Hawaii

to develop a transgenic form of papaya that would be resistant to the virus.

Their approach was to express part of the viral coat protein.

A part of the protein that forms the virus in the plants themselves.

With the idea that this would then give immunity to the plant.

Their approach worked.

And you can see this in the field trials that started already in 1991.

In this picture we can see in the center the transgenic papaya

which is surrounded by non transgenic papaya.

The transgenic papaya have grown and

have thrived, whereas the non transgenic papaya have been decimated by the virus.

Following these field trials, a number of studies were conducted by the USDA.

The Environmental Protection Agency,

which then wanted to show that the papaya did not negatively affect the environment.

The Food and Drug Administration, which then showed that the transgenic

papaya had essentially the identical nutrition and

vitamin content of the non-transgenic papaya,

such that the virus resistant transgenic strain was commercialized in 1998.

It was called rainbow papaya.

And here you can see the effect of the transgenic papaya on the papaya industry.

In 1992, the year that the virus was first found in Puna,

as we said about 53 million pounds of papaya.

Yields went down steadily each year until 1998.

We see it reach approximately 25 millions pounds of papaya.

From that year on as the transgenic growth went more and more into the market,

the papaya yields started recovering.

Until now, over 75% of the papaya fields in Hawaii are transgenic.

The development and release of the transgenic viruses of the papaya strains

saved the Hawaiian papaya industry from disaster.

It also helped reduce the potential spread of viruses

to non transgenic fields by having their resistance spread across the islands.

And this is an excellent example of publicly funded research

based in universities leading to tangible gains in the field.

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