What is your opinion on genetically modified organisms as food? Whether we realise it or not,
genetic modifications to our food have been taking place for a long time through
conventional methods of selective breeding and, more recently, genetic engineering.
Today, the majority of corn, soybean, and canola planted have been genetically modified. Yet,
there are always concerns that widespread consumption of these
genetically modified organisms will lead to health problems on a population level. But
what if they are actually the solution to a long-lasting public health crisis?
Vitamin A deficiency has been a nutritional crisis in developing countries for decades
with severe consequences for young children and pregnant women.
It is the world’s leading preventable cause of childhood blindness and is also associated
with increased morbidity and mortality from common childhood infections. In pregnant women,
insufficient vitamin A intake contributes to maternal mortality and poor outcomes of pregnancy.
Countries afflicted by this often rely on rice as a staple food. Unfortunately,
this promotes vitamin A deficiency because the edible parts of rice (the endosperm) lacks
essential nutrients. Since the rice endosperm does not naturally contain beta-carotene,
which is converted to vitamin A in the human gut, a solution was to genetically
engineer existing cultivars and fortify the rice endosperm with beta-carotene.
This led to the development of Golden Rice by Ingo Potrykus,
Peter Beyer, and their team of researchers.
Golden Rice was designed to increase the dietary intake of vitamin A by
introducing the pathway for beta-carotene synthesis into the rice endosperm. To begin,
immature rice endosperm already contains the first compound, GGPP.
To complete the pathway and produce beta-carotene from GGPP, three foreign genes are inserted
into the rice genome: two genes from the daffodil plant and one from a soil bacterium.
When the gene is expressed,
it produces an enzyme that converts one molecule of the pathway to the next.
But how does this actually happen? Imagine each gene contains the instructions for synthesizing
an enzyme. Rice as an organism already has the basic ingredients and machinery,
they just need to learn how to do it. The genes are packaged into vectors, cargo that
carries not only the gene, but also essential information to mark where the instructions begin.
Next, the vector must be transformed into the rice genome; that is,
the cargo has to be transported into the factory where the work will take place.
This is called Agrobacterium-mediated transformation which is a naturally
occurring method of DNA transfer between bacteria and plants.
Agrobacterium-mediated transformation relies on the T-DNA and the virulence region, two components
of the Ti-plasmid, a circular piece of free DNA in the bacteria. The virulence region is composed
of approximately 30 genes in 7 groups. They are referred to as virulent because when the bacteria
contacts the plant, they encode the enzymes needed to infect the plant and transfer the T-DNA.
The T-DNA stands for Transfer DNA and this is the vector that carries the foreign genes.
This transformation process is complex, with some parts still not fully understood,
but there are generally five stages. First, bacteria attaches to the plant cell. Plant signals
are detected by the bacteria, prompting them to express the virulence region. This produces
proteins which cut the T-DNA region out of the Ti-plasmid and prepares it for transfer. The
T-DNA is transported into the plant cell where it is integrated into the host genome and expressed.
Once this was completed, rice embryos containing all of the inserted genes
were planted and the new seeds they produced were analysed for their beta-carotene content.
Most of the transformed rice endosperm appeared yellow, which indicated the
presence of beta-carotene and led to the name Golden Rice.
One line of transformed plants contained 1.6 micrograms per gram of beta-carotene.
These results did not come easy. It took eight years for the project to come to fruition in 1999,
followed by more years of optimising Golden Rice. Potrykus stated “When we finally had
‘Golden Rice' I learned that even my partner, Peter Beyer… had not believed it would work.”
The research published in 2000 was an incredible landmark. It proved
that beta-carotene could be introduced in the rice grain, which inspired more
scientists to improve the prototype and increase the production of beta-carotene.
Subsequently, the first generation of Golden Rice produced micrograms
per gram of beta-carotene and the second generation produced 31 micrograms per gram.
The Golden Rice Project was the first case of pathway engineering and represented significant
technical advancement, while demonstrating the positive potential of GMO technology.
Despite its initial publicity and efforts of the founders to distribute their invention
to farmers in developing countries free of charge, Golden Rice faced,
and continues to face, enormous backlash from anti-GMO organisations who fear
Golden Rice could become a trojan horse of dangerous genetically engineered food.
In the end, Golden Rice was an epic tale of scientific achievement, but in the real world,
its goal of defeating vitamin A deficiency appears to remain out of reach, even 20 years later.