|Grusak, Michael - Mike|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/7/2006
Publication Date: 7/7/2006
Citation: Grusak, M.A., Tang, G., Russell, R.M. 2006. Golden rice: developments in its biotechnology, safety, and nutritional evaluation. In: Proceedings of the 31st Rice Technical Working Group Meeting, February 26-March 1, 2006, The Woodlands, Texas. Abstract. p. 3. Interpretive Summary:
Technical Abstract: Golden Rice is a transgenic product that was developed to enable the synthesis of beta-carotene in rice grains. Beta-carotene is a yellow-orange carotenoid that can serve as a precursor for vitamin A. Vitamin A deficiency (VAD) is a significant nutritional concern, especially in developing countries where rice is eaten as a staple food crop. Recent estimates indicate that over 250 million people are suffering from VAD. The main cause of VAD is inadequate dietary intake of vitamin A (animal products) or pro-vitamin A carotenoids (plant sources). Low income families throughout the developing world consume limited amounts of animal foods and infrequent amounts of colored fruits and vegetables. For those areas of the world where rice is a staple caloric food source, it was hoped that Golden Rice technology could increase the dietary supply of carotenoids, and diminish the incidence of VAD. The original proof-of-concept version of Golden Rice succeeded in the synthesis and accumulation of beta-carotene and other carotenoids in the endosperm, with total carotenoids reaching 1.6 ug/g DW. More recently, scientists at Syngenta developed a new transgene construct in which a maize gene for phytoene synthase replaced the original daffodil gene. This new product, now known as Golden Rice 2, has resulted in grain carotenoid concentrations as high as 37 ug/g DW, and with beta-carotene representing as much as 84% of the total carotenoids. At these levels, it is estimated that 50% of a 1- to 3-year-old child's RDA for vitamin A (300 ug) could be met with 72 grams of dry rice (a child’s typical portion is 60 grams of rice, and this amount is usually eaten more than once a day). This estimate assumes a 12:1 factor for the conversion of beta-carotene to vitamin A. Although Golden Rice technology works, there are still other issues that need to be addressed. What is the safety of the transgenic product as a human food source? What is the nutritional value of beta-carotene when delivered in a rice endosperm food matrix? And what means are available to transfer this technology to elite cultivars throughout the world? A number of approaches have been used to assess any adverse impacts of transgenic products, including animal-based allergenicity studies, in silico analyses of the allergenicity of predicted peptide fragments from the expressed proteins, safety evaluation of marker genes, and an evaluation of the risk of toxic intake of the synthesized product. In this presentation, we will discuss how these approaches have been used in the case of Golden Rice.