JXB Advance Access originally published online on August 22, 2008
Journal of Experimental Botany 2008 59(13):3551-3562; doi:10.1093/jxb/ern212
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Generation of transgenic maize with enhanced provitamin A content
1Department of Genetics, Development and Cell Biology, 253 Bessey Hall, Iowa State University, Ames, IA 50011, USA
2Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA
3Department of Agronomy, Iowa State University, Ames, IA 50011, USA
* To whom correspondence should be addressed: E-mail: rodermel{at}iastate.edu
Vitamin A deficiency (VAD) affects over 250 million people worldwide and is one of the most prevalent nutritional deficiencies in developing countries, resulting in significant socio-economic losses. Provitamin A carotenoids such as β-carotene, are derived from plant foods and are a major source of vitamin A for the majority of the world's population. Several years of intense research has resulted in the production of ‘Golden Rice 2’ which contains sufficiently high levels of provitamin A carotenoids to combat VAD. In this report, the focus is on the generation of transgenic maize with enhanced provitamin A content in their kernels. Overexpression of the bacterial genes crtB (for phytoene synthase) and crtI (for the four desaturation steps of the carotenoid pathway catalysed by phytoene desaturase and 
-carotene desaturase in plants), under the control of a ‘super 
-zein promoter’ for endosperm-specific expression, resulted in an increase of total carotenoids of up to 34-fold with a preferential accumulation of β-carotene in the maize endosperm. The levels attained approach those estimated to have a significant impact on the nutritional status of target populations in developing countries. The high β-carotene trait was found to be reproducible over at least four generations. Gene expression analyses suggest that increased accumulation of β-carotene is due to an up-regulation of the endogenous lycopene β-cylase. These experiments set the stage for the design of transgenic approaches to generate provitamin A-rich maize that will help alleviate VAD.
Key words:
β-carotene, CRTB, CRTI, -zein promoter, lycopene β-cyclase, provitamin A carotenoids, provitamin A-rich maize, vitamin A deficiency (VAD)
Received 7 May 2008; Revised 15 July 2008 Accepted 15 July 2008
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