Symposium: Plant Breeding: A New Tool for Fighting Micronutrient Malnutrition
Golden Rice: Introducing the ß-Carotene Biosynthesis Pathway into Rice Endosperm by Genetic Engineering to Defeat Vitamin A Deficiency1
Peter Beyer*2, Salim Al-Babili*, Xudong Ye*,, Paola Lucca, Patrick Schaub*, Ralf Welsch* and Ingo Potrykus
* University of Freiburg, Center for Applied Biosciences, D-79104 Freiburg, Germany and the Institute for Plant Sciences, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland
2To whom correspondence should be addressed. E-mail: firstname.lastname@example.org
To obtain a functioning provitamin A (ß-carotene) biosynthetic pathway in rice endosperm, we introduced in a single, combined transformation effort the cDNA coding for phytoene synthase (psy) and lycopene ß-cyclase (ß-lcy) both from Narcissus pseudonarcissus and both under the control of the endosperm-specific glutelin promoter together with a bacterial phytoene desaturase (crtI, from Erwinia uredovora under constitutive 35S promoter control).
This combination covers the requirements for ß-carotene synthesis and, as hoped, yellow ß-carotene-bearing rice endosperm was obtained in the T0-generation. Additional experiments revealed that the presence of ß-lcy was not necessary, because psy and crtI alone were able to drive ß-carotene synthesis as well as the formation of further downstream xanthophylls.
Plausible explanations for this finding are that these downstream enzymes are constitutively expressed in rice endosperm or are induced by the transformation, e.g., by enzymatically formed products. Results using N. pseudonarcissus as a model system led to the development of a hypothesis, our present working model, that trans-lycopene or a trans-lycopene derivative acts as an inductor in a kind of feedback mechanism stimulating endogenous carotenogenic genes.
Various institutional arrangements for disseminating Golden Rice to research institutes in developing countries also are discussed.
© 2002 The American Society for Nutritional Sciences J. Nutr. 132:506S-510S, 2002
Organic Consumers Organization
Source: ISIS, 8/03 UK
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