Generation of transgenic maize with enhanced provitamin A content

J Exp Bot. 2008;59(13):3551-62. doi: 10.1093/jxb/ern212. Epub 2008 Aug 22.


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 beta-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 zeta-carotene desaturase in plants), under the control of a 'super gamma-zein promoter' for endosperm-specific expression, resulted in an increase of total carotenoids of up to 34-fold with a preferential accumulation of beta-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 beta-carotene trait was found to be reproducible over at least four generations. Gene expression analyses suggest that increased accumulation of beta-carotene is due to an up-regulation of the endogenous lycopene beta-cylase. These experiments set the stage for the design of transgenic approaches to generate provitamin A-rich maize that will help alleviate VAD.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alkyl and Aryl Transferases / genetics
  • Alkyl and Aryl Transferases / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Erwinia / enzymology
  • Genetic Engineering*
  • Geranylgeranyl-Diphosphate Geranylgeranyltransferase
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / metabolism
  • Transformation, Genetic
  • Zea mays / genetics*
  • Zea mays / metabolism*
  • beta Carotene / biosynthesis*
  • beta Carotene / genetics


  • Bacterial Proteins
  • beta Carotene
  • Alkyl and Aryl Transferases
  • Geranylgeranyl-Diphosphate Geranylgeranyltransferase