Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA.
Mol Plant. 2010 Jan;3(1):66-77. doi: 10.1093/mp/ssp057. Epub 2009 Aug 3.
Little is known about how plants regulate their folate content, including whether the expression of folate biosynthesis genes is orchestrated during development or modulated by folate levels. Nor is much known about how folate levels impact the expression of other genes. These points were addressed using wild-type tomato fruit and fruit engineered for high folate content. In wild-type fruit, the expression of genes specifying early steps in folate biosynthesis declined during development but that of other genes did not. In engineered fruit overexpressing foreign GTP cyclohydrolase I and aminodeoxychorismate synthase genes, the expression of the respective endogenous genes did not change, but that of three downstream pathway genes-aminodeoxychorismate lyase, dihydroneopterin aldolase, and mitochondrial folylpolyglutamate synthase-respectively increased by up to 7.8-, 2.8-, and 1.7-fold, apparently in response to the build-up of specific folate pathway metabolites. These results indicate that, in fruit, certain folate pathway genes are developmentally regulated and that certain others are subject to feedforward control by pathway intermediates. Microarray analysis showed that only 14 other transcripts (of 11 000 surveyed) increased in abundance by two-fold or more in high-folate fruit, demonstrating that the induction of folate pathway genes is relatively specific.
关于植物如何调节其叶酸含量，人们知之甚少，包括叶酸生物合成基因的表达是否在发育过程中协调，或者是否受叶酸水平的调节。人们对叶酸水平如何影响其他基因的表达也知之甚少。这些问题是使用野生型番茄果实和工程果实来解决的，这些果实的叶酸含量很高。在野生型果实中，叶酸生物合成早期步骤的基因表达在发育过程中下降，但其他基因的表达没有下降。在过表达外源 GTP 环化水解酶 I 和氨基脱氧胆色素合酶基因的工程果实中，各自的内源性基因的表达没有变化，但三个下游途径基因——氨基脱氧胆色素裂解酶、二氢乳清酸醛缩酶和线粒体叶酸多谷氨酸合酶的表达分别增加了 7.8 倍、2.8 倍和 1.7 倍，显然是对特定叶酸途径代谢物的积累的反应。这些结果表明，在果实中，某些叶酸途径基因受到发育调控，而其他基因则受到途径中间产物的前馈控制。微阵列分析显示，在高叶酸果实中，只有 14 个其他转录本（在调查的 11000 个转录本中）的丰度增加了两倍或更多，这表明叶酸途径基因的诱导相对特异。
