Genetic Engineering of “Golden Rice” Presenter: Meng Li

Background Information The inventors of Golden Rice were Ingo Potrykus, Professor emeritus of the Institute for Plant Sciences of the Swiss Federal Institute of Technology, and Professor Peter Beyer, of the Centre for Applied Biosciences, University of Freiburg, Germany The research for a Golden Rice started off as a Rockefeller Foundation initiative in

Background Information Vitamin A is essential for eye health and the proper functioning of the immune system. It is found in foods such as milk, liver, eggs, red and orange fruits, red palm oil and green leafy vegetables. Vitamin A deficiency (VAD) is prevalent among the poor whose diets are based on rice sources. Rice does not contain any β-carotene (provitamin A) in grain. VAD could caused night blindness, complete blindness, and affecting on immune system.

Background Information In 2012 the World Health Organization reported that about 250 million preschool children are affected by VAD. Yearly, half a million people—mainly children— become blind as a consequence of VAD, 50 percent of which die within a year of becoming blind.

WHO

The Golden Rice Project The goal is to provide the recommended daily allowance of vitamin A (600 µg ) in g of β- carotene-containing rice. A prototype Golden Rice was developed in 1999, and new lines with higher β-carotene content have been generated. Golden Rice grains are easily recognizable by their yellow to orange color, the stronger the color the more β- carotene.

Achieve the Goal Rice produces β-carotene in the leaves but not in the grain, where the biosynthetic pathway is turned off during plant development. Two genes have been inserted into the rice genome by genetic engineering, to restart the carotenoid biosynthetic pathway leading to the production and accumulation of β-carotene in the grains.

To produce Golden Rice, 2 enzymes are introduced into the endosperm [phytoene synthase (psy) and phytoene desaturase (crtl)] via an endosperm-specific glutelin (Gtl) promoter, to establish a b-carotene biosynthetic pathway in the rice grains. Genetic Engineering

Golden Rice The first generation of Golden Rice is SGR1 (1999) SGR1 contained the phytoene synthase (psy) gene from daffodil and the carotene desaturase (crtI) gene from the bacterium Erwinia uredovora Both genes were expressed only in the rice endosperm. The carotenoids level in field production of SGR1 were up to 1.6 µg/g

Gene construct used to generate SGR1. RB, T-DNA right border sequence; Glu, rice endosperm-specific glutelin promoter; tpSSU, pea ribulose bis-phosphate carboxylase small subunit transit peptide for chloroplast localisation; nos, nopaline synthase terminator; Psy, phytoene synthase gene from Narcissus pseudonarcissus (GR1) or Zea mays (GR2); Ubi1, maize polyubiquitin promoter; Pmi, phosphomannose isomerase gene from E. coli for positive selection (GR2); LB, T-DNA left border sequence.

Golden Rice Today The bottleneck of SGR1 was the enzymatic activity of PSY. Golden Rice–2 was transformed with a construct containing a phytoene synthase gene from maize and contains up to 35 µg β- carotene per gram of dry rice.

Testing the Performance of Golden Rice The first human test of Golden Rice-2 by Guangwen in China, 2012.

Experiment Golden Rice plants were grow hydroponically with heavy water to generate deuterium-labeled β-carotenein in rice grains. Golden Rice servings of 65–98 g (130–200 g cooked rice) containing 0.99–1.53 mg b-carotene were fed to 5 healthy adult volunteers with 10 g butter. Blood samples were collected over 36 d.

Results: results showed that the mean area under the curve for the total serum response to deuterium was 39.9 µg·d after the Golden Rice dose. β -Carotene derived from Golden Rice is effectively converted to vitamin A in humans.

Questions about Golden Rice Biosafety: effect of the genes if outcrossing occurred Health Effects: food safety Financial support for poor and developing countries

References: 1. Peter Beyer, Salim Al-Babili, Xudong Ye and Ingo Potrykus, et al. 2002, Symposium: Plant Breeding: A New Tool for FightingMicronutrient Malnutrition, The Journal of Nutrition, 132: 506s-510S. 2. Guangwen Tang, Yuming Hu, Michael A Grusak, and Robert M Russell, et al., 2012, b-Carotene in Golden Rice is as good as b-carotene in oil at providing vitamin A to children, The American Journal of Clinical Nurtion, 96: Guangwen Tang, Gregory G Dolnikowski,, and Michael A Grusak, et al., 2009, Golden Rice is an effective source of vitamin A, The American Journal of Clinical Nurtion, 2009:89: