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Golden rice is a variety of rice (''Oryza sativa'') produced through genetic engineering to biosynthesize beta-carotene, a precursor of vitamin A, in the edible parts of rice. The research was conducted with the goal of producing a fortified food to be grown and consumed in areas with a shortage of dietary vitamin A,〔One existing crop, genetically engineered "golden rice" that produces vitamin A, already holds enormous promise for reducing blindness and dwarfism that result from a vitamin-A deficient diet. - Bill Frist, physician and politician, in a ''Washington Times'' commentary - November 21, 2006 ()〕 a deficiency which is estimated to kill 670,000 children under the age of 5 each year.〔Black RE et al., Maternal and child undernutrition: global and regional exposures and health consequences, The Lancet, 2008, 371(9608), p. 253.〕 Golden rice differs from its parental strain by the addition of three beta-carotene biosynthesis genes. The scientific details of the rice were first published in ''Science'' in 2000,〔 the product of an eight-year project by Ingo Potrykus of the Swiss Federal Institute of Technology and Peter Beyer of the University of Freiburg. At the time of publication, golden rice was considered a significant breakthrough in biotechnology, as the researchers had engineered an entire biosynthetic pathway. In 2005, a new variety called ''Golden Rice 2'', which produces up to 23 times more beta-carotene than the original golden rice, was announced. Although golden rice was developed as a humanitarian tool, it has met with significant opposition from environmental and anti-globalization activists. Studies have found that golden rice poses no risk to human health, and multiple field tests have taken place with no adverse side-effects to participants.〔(PhilRice Two seasons of Golden Rice trials in Phl concluded ), 09 June 2013.〕 Golden Rice was one of seven winners of the 2015 Patents for Humanity Awards by the United States Patent and Trademark Office.〔(【引用サイトリンク】title=Patents for Humanity Awards 2015 )〕〔(【引用サイトリンク】title=Patents for Humanity Awards Ceremony at the White House )〕 ==Creation== Golden rice was designed to produce beta-carotene, a precursor of vitamin A, in the edible part of rice, the endosperm. The rice plant can naturally produce beta-carotene in its leaves, where it is involved in photosynthesis. However, the plant does not normally produce the pigment in the endosperm, where photosynthesis does not occur. A key breakthrough was the discovery by Peter Bramley that a single phytoene desaturase gene (bacterial ''CrtI'') can be used to produce lycopene from phytoene in GM tomato, rather than having to introduce the multiple carotene desaturases that are normally used by higher plants. Lycopene is then cyclized to beta-carotene by the endogenous cyclase in Golden Rice.〔(【引用サイトリンク】url=http://www.goldenrice.org/Content2-How/how1_sci.php )〕 Golden rice was created by transforming rice with only two beta-carotene biosynthesis genes: #''psy'' (phytoene synthase) from daffodil (''Narcissus pseudonarcissus'') #''crtI'' (carotene desaturase) from the soil bacterium ''Erwinia uredovora'' (The insertion of a ''lcy'' (lycopene cyclase) gene was thought to be needed, but further research showed it is already being produced in wild-type rice endosperm.) The ''psy'' and ''crtI'' genes were transformed into the rice nuclear genome and placed under the control of an endosperm-specific promoter, so 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 formation occurs. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Golden rice」の詳細全文を読む スポンサード リンク
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