Ye, X S' AlBabili, A' Kloti, J' Zhang, P' Lucca, P' Beyer, and I' Potrykus' 2000' Engineering the pr

1
Ye, X S. Al-Babili, A. Kloti, J. Zhang, P.
Lucca, P. Beyer, and I. Potrykus. 2000.
Engineering the pro-vitamin A (beta-carotene)
biosynthetic pathway into (carotenoid-free) rice
endosperm. Science 287 (5451) 303. 

• Presented by
• Igy Martinez

2
VITAMIN A DEFICIENCY

• 124 million children affected worldwide
• 1 to 2 million deaths per year among children
• Major cause of seeing disorders
• Other afflictions
• Prevalent in 26 countries where rice is a major
  food staple

3
RICE (ORYZA SATIVA)

• Primary food source in over ½ the world
  population
• Poor source of essential nutrients
• Vitamin A deficient
• Synthesizes GGPP

4
Rational

• Combat malnutrition
• Find alternatives to deliver vitamin A in
  underdeveloped countries
• Supplement rice endosperm with vitamin A

5
Beta Carotene Biosynthetic Pathway
6
Isolated Enzymes
7
Recombinant DNA Technology

• Three rice groups tested
• Control group with no transformation
• Single group that underwent one transformation
  carrying a combination of three vectors
• Double group that underwent two transformations
  each carrying one vector

• Vector Sequencing
• Three vectors in single transformation group
  combined sequencing for phytoene synthase from
  daffodil and phytoene desaturase from Erwinia
  bacterium
• One vector in the co-transformation group
  sequenced phytoene synthase and phytoene
  desaturase while the second vector sequenced
  lycopene beta cyclase

8
Golden Rice

• Single transformant line revealed 31
  colored/uncolored ratio.
• Co-transformant line were all variably colored.
• Vitamin A synthesized in both lines.
• Transgenic rice plants showed normal vegetation
  and were fertile.

9
HPLC Results

• Both transformed lines detected beta carotene,
  lutein, and zeaxanthin
• None of the transformed lines detected lycopene
  beta cyclase

10
Relevance

• GGPP in rice endosperm can be successfully
  converted to pro-vitamin A.
• The detection of pro-vitamin A in both
  transformed groups indicates that the enzymes
  necessary to convert lycopene into pro-vitamin A
  are already expressed in normal rice endosperm.