<P> (The insertion of a lcy (lycopene cyclase) gene was thought to be needed, but further research showed it is already produced in wild - type rice endosperm .) </P> <P> The psy and crtI genes were transferred into the rice nuclear genome and placed under the control of an endosperm - specific promoter, so that they are only expressed in the endosperm . The exogenous lcy gene has a transit peptide sequence attached, so it is targeted to the plastid, where geranylgeranyl diphosphate is formed . The bacterial crtI gene was an important inclusion to complete the pathway, since it can catalyze multiple steps in the synthesis of carotenoids up to lycopene, while these steps require more than one enzyme in plants . The end product of the engineered pathway is lycopene, but if the plant accumulated lycopene, the rice would be red . Recent analysis has shown the plant's endogenous enzymes process the lycopene to beta - carotene in the endosperm, giving the rice the distinctive yellow color for which it is named . The original golden rice was called SGR1, and under greenhouse conditions it produced 1.6 μg / g of carotenoids . </P> <P> The research that led to golden rice was conducted with the goal of helping children who suffer from vitamin A deficiency (VAD). In 2005, 190 million children and 19 million pregnant women, in 122 countries, were estimated to be affected by VAD . VAD is responsible for 1--2 million deaths, 500,000 cases of irreversible blindness and millions of cases of xerophthalmia annually . Children and pregnant women are at highest risk . Vitamin A is supplemented orally and by injection in areas where the diet is deficient in vitamin A . </P> <P> As of 1999, 43 countries had vitamin A supplementation programs for children under 5; in 10 of these countries, two high dose supplements are available per year, which, according to UNICEF, could effectively eliminate VAD . However, UNICEF and a number of NGOs involved in supplementation note more frequent low - dose supplementation is preferable . </P>

Golden rice was developed to help with blindness caused by a deficiency of which vitamin