Last updated on April 18, 2014 at 15:11 EDT

Golden Rice

Golden Rice is a variety of Oryza sativa rice produced  through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of the rice. The research was conducted with the goal of producing a fortified food to be grown and consumed in areas with a shortage of dietary vitamin A, a deficiency which is estimated to kill 670,000 children under five years old each year.

Golden rice is different from its parental strain by the addition of three beta-carotene biosynthesis genes. The scientific details of the rice were initially published in Science in 2000, the product of an eight-year project by Ingo Potrykus of the Swiss Federal Institute of Technology and Peter Beyer of the University of Freiburg. At the time of the publication, golden rice was considered a significant breakthrough in biotechnology, as the researchers had engineered an entire biosynthetic pathway.

In 2005, a new variety named Golden Rice 2, which produces up to 23 times more beta-carotene than the original golden rice, was revealed. Although Golden Rice was developed as a humanitarian tool, it has been met with substantial opposition from environmental and anti-globalization activists. Golden Rice has undergone 2 years of field testing within the Philippines.

Golden Rice was designed to generate beta-carotene, a precursor of vitamin A, in the edible portion of the rice, the endosperm. The rice plant can naturally create beta-carotene within its leaves, where it’s involved in photosynthesis. However, the plant doesn’t normally produce the pigment in the endosperm, where photosynthesis doesn’t take place. A crucial breakthrough was the discovery that a single phytoene desaturase gene (bacterial CrtI) can be utilized to create lycopene from phytoene in GM tomato, as opposed to having to introduce the multiple carotene denaturizes that are usually utilized by higher plants. Lycopene is then cyclized to beta-carotene via the endogenous cyclase in Golden Rice.

The Golden Rice was created by transforming rice with only two beta-carotene biosynthesis genes: psy (phytoene synthase) from daffodil (Narcissus pseudonarcissus) and crtI (carotene desaturase) from the soil bacterium Erwinia uredovora. The insertion of a lyc (lycopene cyclase) gene was thought to be required, but further research proved it’s already being produced in wild-type rice endosperm.

The psy and crtI genes were transformed into the rice nuclear genome and placed under the control of an endosperm-specific promoter, so they are only expressed in the endosperm. The exogenous lyc gene has a transit peptide sequence connected so it is targeted to the plastid, where geranylgeranyl diphosphate formation takes place. The bacterial crtI gene was a significant inclusion to accomplish the pathway, since it can catalyze multiple steps in the synthesis of carotenoids up to lycopene, while these steps need more than one enzyme in plants. The end product of the engineered pathway is lycopene, but if the plant accumulated lycopene, the rice would be colored red. Recent analysis has shown the plant’s endogenous enzymes process the lycopene to beta-carotene in the endosperm, giving the rice the distinguishing yellow color for which it is named. The original Golden Rice was named SGR1, and under greenhouse conditions it generated 1.6 micrograms per gram of carotenoids.

Golden Rice has been bred with local rice cultivars within the Philippines, Taiwan, and with the American rice cultivar ‘Cocodrie’. The first field trials of these golden rice cultivars were performed by Louisiana State University Agricultural Center in 2004. Field testing supplies a more accurate measurement of nutritional value and permits feeding tests to be performed. Initial results from the field tests have displayed field-grown golden rice produces four to five times more beta-carotene than golden rice that is grown under greenhouse conditions.

In 2005, a team of researchers at biotechnology company, Syngenta, created a variety of golden rice named “Golden Rice 2”. They joined the phytoene synthase gene from maize with crtI from the original golden rice. Golden Rice 2 produces 23 times more carotenoids than golden rice, and preferentially accumulates beta-carotene. To receive the Recommended Dietary Allowance, it’s estimated that 144 grams of the most high-yielding strain would have to be consumed. Bioavailability of the carotene from golden rice has been established and found to be an effective source of Vitamin A for humans.

In June of 2005, researcher Peter Beyer received funding form the Bill and Melinda Gates Foundation to further enhance golden rice by increasing the levels of the bioavailability of pro-vitamin A, vitamin E, iron, and zinc, and to enhance protein quality through genetic modification.

The research that led to golden rice was performed with the objective of helping children who suffer from vitamin A deficiency (VAD). In 2005, 190 million children and 19 million pregnant women, in 122 countries, were estimated to be affected by vitamin A deficiency. VAD is held responsible for 1 to 2 million deaths, 500,000 cases of irreversible blindness and millions of cases of xerophthalmia annually. Children and women who are pregnant are at the highest risk. Vitamin A is supplemented orally and by injection in areas where the diet is lacking Vitamin A. As of 1999, there were 43 countries that had vitamin A supplementation programs for children under the age of 5; in 10 of these countries, two high dose supplements are obtainable per year, which, according to UNICEF, could efficiently eradicate VAD. However, UNICEF and numerous NGOs involved in supplementation note more frequent low-dose supplementation must be an objective where it is possible.

Because many children within countries where there is a dietary deficiency in vitamin A depend on rice as a staple food, the genetic modification to make rice produce the vitamin A precursor beta-carotene is seen as an effortless and less expensive alternative to vitamin supplements or an increase in the consumption of green vegetables or animal products. It can be considered as the genetically engineered equivalent of fluoridated water or iodized salt in that it aids in preventing disease, with the exception that fluoride isn’t an elemental nutrient for survival.

Initial analysis of the potential nutritional benefits of golden rice proposed consumption of golden rice wouldn’t get rid of the issues of vitamin A deficiency, but should be seen as a complement to other techniques of vitamin A supplementation. Since then, improved strains of golden rice have been developed having adequate provitamin A to provide the total dietary requirement of this nutrient to people who eat about 75 grams of golden rice each day.

Particularly, since carotenes are hydrophobic, there needs to be an adequate amount of fat present within the diet for golden rice to have the ability to lessen vitamin A deficiency. In that respect, it’s significant that vitamin A deficiency is rarely an isolated phenomenon, but normally coupled to a general lack of a balanced diet. The RDA levels accepted in developed countries are far in excess of the amounts required to prevent blindness. Furthermore, this claim referred to an early cultivar of golden rice; one bowl of the latest version provides 60 percent of RDA for healthy children.

Critics of genetically engineered crops have raised a variety of concerns. One of these is that golden rice originally didn’t have sufficient vitamin A. This issue was solved by the development of new strains of rice. Nonetheless, there are still doubts about the speed at which vitamin A degrades once the plant is harvested, and how much remains after cooking it. A study in 2009 concluded that golden rice is successfully converted into vitamin A in humans and a 2012 study that fed 68 children ages 6 to 8 concluded that golden rice was as good as vitamin A supplements and better than the natural beta-carotene in spinach.

Greenpeace opposes the release of any genetically modified organisms into the environment and is concerned that golden rice is a Pandora’s Box that will open the door to more common usage of GMOs.

Vandana Shiva, an Indian anti-GMO activist, argued that the issue wasn’t that the crop had any particular deficiencies, but that there were potential issues with poverty and loss of biodiversity in food crops. These issues are aggravated by the corporate control of agriculture by means of controlling genetically modified organisms. By concentrating on a narrow issue (vitamin A deficiency), Shiva argued, the golden rice proponents were obscuring the larger issue of a lack of broad availability of diverse and nutritionally sufficient food sources. Other groups argued that a varied diet containing foods that are rich in beta carotene such as sweet potatoes, leafy green vegetables, and fruit would supply children with adequate vitamin A. However, Keith West of Johns Hopkins Bloomberg School of Public Health has argued that foodstuffs containing vitamin A are either not available, or only available in certain seasons, or that they are too expensive for poor families in underdeveloped countries.

Due to a lack of real-world studies and uncertainty about how many people will use golden rice, WHO malnutrition expert Francesco Branca concludes “giving out supplements, fortifying existing foods with vitamin A, and teaching people to grow carrots or certain leafy vegetables are, for now, more promising ways to fight the problem”. More recently, author Michael Pollan, who had attacked the product in the year 2001, while still doubtful about the benefits, expressed support for the continuance of the research.

An experimental plan of golden rice being grown within the Philippines was uprooted during direct action on August 8, 2013. While the action was, at first, credited to 400 local farmers, it was later found to have been performed by a group of 50 anti-GMO activists.

Potrykus has organized an effort to have golden rice distributed for free to subsistence farmers. Free licenses for developing countries were arranged quickly due to the positive publicly that golden rice received, especially in Time magazine in July of 2000. Golden Rice was said to be the first recombinant DNA tech crop that was unarguably advantageous. Monsanto Company was one of the first companies to permit free licenses. The cutoff between humanitarian and commercial use was set at 10,000 US dollars. Thus, as long as a farmer or subsequent user of Golden Rice genetics doesn’t make more than 10,000 dollars per year, no royalties need to be paid. Additionally, farmers are allowed to keep and replant seed.

Image Caption: Golden Rice grain compared to white rice grain in screenhouse of Golden Rice plants. Credit: International Rice Research Institute (IRRI)/Wikipedia (CC BY 2.0)

Golden Rice