Brussels, 5th August 1999
"Yellow rice" to prevent vitamin A deficiency
A project funded by the European Union - Carotene plus - has successfully incorporated the production of ß-carotene into rice. This major scientific achievement, which incidentally turns the rice grains yellow, will help prevent severe vitamin A deficiency in countries relying on rice as a staple food.
Vitamin A deficiency is a public health problem in 118 countries. Not only does it cause xerophthalmia the leading cause of childhood blindness in developing countries but it also has broader consequences in terms of child morbidity and mortality by leading to greater susceptibility to various diseases such as respiratory infections, diarrhoea and measles. According to the World Health Organisation (WHO), between 140 and 250 million pre-school children are deficient in vitamin A world-wide . Improving the vitamin A status of pre-school children reduces mortality by 23%, measles mortality by 50% and diarrhoeal disease mortality by 33%. It also reduces the severity of childhood infectious diseases, in particular diarrhoea and measles. Another report suggests that improved vitamin A intake would prevent 1.25-3.5 million of the nearly 8 million late infancy and pre-school-age child deaths that occur each year in the highest-risk developing countries.
However, as supplements are difficult to distribute effectively, and costly to administer, an alternative way to defeat severe vitamin A deficiency is to introduce it directly into the diet via rice, for example, which is the major staple food for over two billion people.
A breakthrough in pathway engineering
The "Carotene plus" research project has succeeded in modifying rice by genetic engineering to make it produce ß-carotene (provitamin A) which is converted to vitamin A by humans. As a result of the carotene content the rice is yellow. This rice can be considered as a functional food a new category of food products providing specific health benefits. It contains enough ß-carotene to meet total vitamin A requirements in a typical Asian diet.
The strategy used was to introduce the genes corresponding to the complete biosynthesis pathway into the rice genome, so that ß-carotene could be produced in the rice endosperm. Technically the work consisted of isolating the genes coding for the enzymes required to produce ß-carotene. Four plant genes, namely phytoene synthase, phytonene desaturase, zeta carotene desaturase and lycopene cyclase are theoretically required. However, by using a bacterial phytoene desaturase capable of replacing the two plant desaturase genes, only three genes were finally necessary to achieve ß-carotene production. The two plant genes were from Narcissus pseudonarcissus (daffodil).
Like any other plant, rice is capable of synthesising ß-carotene in its green parts. However, the edible part of rice grains the so-called endosperm is carotenoid-free. The use of endosperm-specific promoters, regulating the activity of the ß-carotene biosynthesis genes ensures ß-carotene production in this specific tissue leading to a yellow appearance of the milled grains. Rice grains are traditionally consumed in the milled form, a process in which the outer layers are removed thereby also discarding many compounds with high nutritional value. The reason for milling is to remove a fat-rich outer layer that rapidly turns rancid during storage, especially in tropical and sub-tropical climates.
The responsible action of the scientists involved means that the plants have been grown in full compliance with EU and national legislation, i.e. using contained facilities. No application has yet been made to release the plants into the environment under the Deliberate Release Directive or their safety for human consumption assessed under the Novel Foods Regulation . Furthermore, no transfer of the technology to developing countries will be made until full compliance with all European safety legislation has been ensured.
A continuing effort
The "yellow rice" now available must be further developed. Using traditional breeding techniques, the trait will be transferred to rice varieties adapted to local conditions. Once the nutritional and environmental properties have been carefully examined, free access to the seed is to be given to subsistence farmers in developing countries.
The "Carotene plus" project also provides for the introduction of ß-carotene biosynthesis into tissues that are carotene-free in other crops, including many other cereals, the aim being to develop functional foods by adding compounds known to have a positive effect on human health due to their antioxidant properties and their provitamin A character.
This project is currently funded by the European Commission through its FAIR programme and its initial phase was supported by the Rockefeller Foundation.
For further information, please contact:
Stéphane Hogan, Quality of Life programme, DG XII
Tel: +32-2-296.29.65; Fax: +32 2 299.1860
Stephen Gosden, Communication Unit, DG XII
Tel : +32-2-296.00.79; Fax: +32-2-295.82.20