So you want to know how a GMO is made? You’re not alone. It’s one of the top questions
about biotechnology. There are different ways plants can be genetically engineered. We’ll
use the story of the papaya in Hawaii to walk you through one of them.
Step 1: Determine whether genetic engineering is the most effective way to solve a plant’s
problem, such as a disease or damage from pests.
For centuries, traditional plant breeding has been used to fight pests, environmental
stress (such as drought), as well as to improve taste and nutrition.The reasons to develop
GMOs are no different today, but GMOs can be created more quickly and more precisely.
Other breeding methods can take decades to produce results and aren’t able to be as
precise and focusing on one genetic trait or isolating a solution to a specific problem.
Since the 1940s, the Hawaiian papaya industry had been battling a problem: the destructive
and rapidly spreading papaya ringspot virus (AKA PRSV). PRSV deforms the papaya fruit
and in young plants, destroys the plant’s ability to produce fruit at all. PRSV is transmitted
by insects that feed on the fruit. Many methods were deployed to try to stop the destructive
virus. In the early 1960s, farmers moved papaya production from one Hawaiian island
to another; from the island of Oaha to the big island of Hawaii in the Puna district.
The virus ultimately reached Puna. Other methods didn’t work either, including using insecticides
for the insects spreading the virus, giving the plants a mild strain of the virus to create
natural inoculation, or destroying infected trees. The virus just continued to spread.
53 million pounds of fresh papaya were being produced annually when PRSV was first discovered
in Puna in 1992. By 1998 that amount had been cut in half to 26 million pounds. The crops
and livelihood of farmers were being destroyed in front of their eyes. Moreover, for consumers,
the availability of fresh papaya and papaya juice for fruit salads, smoothies and other
products were threatened.
A powerful new tool – biotechnology was now available to fight back. Farmers and researchers
turned to genetic engineering, beginning in 1985, for help.
Step 2: Identify the gene or genetic material that could solve the problem, like providing
resistance to the disease or pest and study the genetic make-up of the plant that needs
the trait.
Researchers and farmers had to find a way to make the papaya plant resistant to the
deadly virus. PRSV resistance was the genetic trait needed to solve the problem. Researchers
knew that if plants contain certain genetic material from the virus within their own DNA,
they were protected. If they could insert a copy of this gene from the virus itself
into the papaya’s genetic make-up, the plants would be protected.
Step 3: Copy the trait from a donor organism and implant it into the plant’s DNA.
Researchers isolated a PRSV gene from the virus itself. Then, they needed a way to get
the genetic material into the papaya plant’s own DNA. Researchers deployed a commonly used
technique in biotechnology called transformation; a process by which a copy of genetic material
from a specific trait is inserted into cells. There are many ways to transform a cell. In
this case, the researchers used a high-speed particle bombardment method, through a high-pressure
insertion device. The gene from the virus was inserted into the DNA of the papaya seed.
The genetic material made the plant resistant to the ringspot virus, just as a flu shot
makes people resistant to the flu.
The researchers were able to successfully transform 17 plants. These plants contained
this gene from the virus and produced a protein from the virus that helped the plants become
resistant to the PRSV infection.
Step 4: Plant the new seed and test it.
The final step was to plant the seeds and carefully test the resulting plants. One line
of plants demonstrated consistent resistance to the virus. After several years of testing,
it was determined that this line performed well on the farms, was safe for people to
eat and was of commercial quality. Success was achieved.
One variety of transgenic papaya, the “Rainbow”, yielded about 125,000 pounds of marketable
fruit, per acre, per year; 25 times the amount of fruit produced per acre by a non-GM variety
infected by PRSV. These tests took about seven years, including food safety and environmental
review by the FDA, USDA and EPA. Once regulatory approval was gained, the Hawaiian farmers
chose to start using the new papaya seeds. The result? The harvesting of the new PRSV-resistant
papaya began in 1998 and, by 2001, the industry had rebounded, producing 46 million pounds
of fresh papaya free of PRSV. This kept the vibrant papaya industry alive in Hawaii and
ensured consumers had access to high-quality papaya and papaya juice at a reasonable cost.
Genetic engineering allowed the introduction of PRSV resistance, without altering other
traits of the papaya or changing the plants in other ways. The plants were exactly the
same in nutrition and safety.
As of 2010, 70% of Hawaii’s papaya industry is GM papaya. GM papaya has been grown and
consumed in the US for more than a decade. This is just one GMO story. We hope to share
more with you. Please share your comments.