俺在下面的贴里说：
• 水稻叶本身是合成胡萝卜素的。黄金大米只是激活了米胚中的胡萝卜素合成。 - 26484915 - ♂ 
(688 bytes) (12 reads) 09/04/2014 11:11:27
(0 bytes) (3 reads) 09/04/2014
俺想请教一下：哪里理解不对？
Golden Rice technology is based on the simple principle that rice plants possess the whole machinery to synthesise β-carotene, and while this machinery is fully active in leaves, parts of it are turned off in the grain. By adding only two genes, a plant phytoene synthase (psy) and a bacterial phytoene desaturase (crt I), the pathway is turned back on and β-carotene consequently accumulates in the grain.
金稻米技术的产生基于一个简单的原理，水稻只能在绿叶组织中合成 β-胡萝卜素，而在被食用的胚乳中 却没有，可是这个两步的生物合成 途径确实存在于粮食中。仅仅通过 转入两种酶的基因：八氢番茄红素 合成酶（PSY）和八氢番茄红素脱氢酶 （crt I），粮食中可以合成β-胡萝卜素 的途径就能被重新激活，β-胡萝卜 素就能因此在被食用的胚乳中制造 并积累。
Fig 1: Pathway overview: carotenoid biosynthesis begins with a small (C5) compound, isopentenyl-diphosphate (IPP) and its isomer dimethylally-diphosphate (DMAPP). Chain elongation by C5 units leads to the formation of the C20-compound geranylgeranyl-diphosphate (GGPP). GGPP is a precursor that can enter several biosynthetic routes, as indicated. The head-to-head condensation of two GGPP molecules produces the first,colourless carotene, phytoene. A series of desaturation reactions lead to the coloured chromophore of lycopene, and subsequent cyclization reactions produce the β- and ε-ionone rings. Oxygenation (hydroxylation, epoxidation) reactions lead then to xanthophylls. Several known pathways branch off at this point, forming biologically important molecules, such as abscisic acid and strigolactones
(http://www.goldenrice.org/Content2-How/how1_sci.php)
