Enhanced flux through the methylerythritol 4-phosphate pathway in Arabidopsis plants overexpressing deoxyxylulose 5-phosphate reductoisomerase
Enhanced flux through the methylerythritol 4-phosphate pathway in Arabidopsis plants overexpressing deoxyxylulose 5-phosphate reductoisomerase
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DOI：
10.1007/s11103-006-9051-9
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发表时间：
2006-11-01
影响因子：
5.1
通讯作者：
Rodriguez-Concepcion, Manuel
中科院分区：
文献类型：
--
作者：
Carretero-Paulet, Lorenzo;Cairo, Albert;Rodriguez-Concepcion, Manuel
甲基赤藓糖醇4-磷酸（MEP）途径合成了种类繁多的质体类异戊二烯的前体，包括主要的光合色素叶绿素和类胡萝卜素。由于确定了该途径的前两个酶，脱氧纤维素5-磷酸（DXP）合成酶（DXS）和DXP还原异构酶（DXR），它们都被认为是潜在的控制点。在所有测试的系统中，DXS活性的增加已被证明可以上调质体类异戊二烯的产生，但DXR对类异戊二烯前体供应的相对贡献尚不清楚。在这项工作中，我们培育了转基因拟南芥植株，其DXS和DXR酶水平分别通过对氯马酮和磷米霉素的抗性来估计。DXR的下调导致叶绿体发育出现斑纹、色素沉着减少和缺陷，而DXR过表达的转基因植株在产生这种非原生类异戊二烯的转基因植株中，mep衍生质体类异戊二烯如叶绿素、类胡萝卜素和taxadi烯的积累增加。转基因植株中DXR水平的变化并未导致DXS基因表达和酶积累的变化，这证实了DXR过表达系质体类异戊二烯水平的变化并非DXS水平改变的间接后果。结果表明，MEP的生物合成限制了拟南芥叶绿体下游类异戊二烯的产生，支持DXR通过MEP途径控制代谢通量的作用。
The methylerythritol 4-phosphate (MEP) pathway synthesizes the precursors for an astonishing diversity of plastid isoprenoids, including the major photosynthetic pigments chlorophylls and carotenoids. Since the identification of the first two enzymes of the pathway, deoxyxylulose 5-phoshate (DXP) synthase (DXS) and DXP reductoisomerase (DXR), they both were proposed as potential control points. Increased DXS activity has been shown to up-regulate the production of plastid isoprenoids in all systems tested, but the relative contribution of DXR to the supply of isoprenoid precursors is less clear. In this work, we have generated transgenic Arabidopsis thaliana plants with altered DXS and DXR enzyme levels, as estimated from their resistance to clomazone and fosmidomycin, respectively. The down-regulation of DXR resulted in variegation, reduced pigmentation and defects in chloroplast development, whereas DXR-overexpressing lines showed an increased accumulation of MEP-derived plastid isoprenoids such as chlorophylls, carotenoids, and taxadiene in transgenic plants engineered to produce this non-native isoprenoid. Changes in DXR levels in transgenic plants did not result in changes in DXS gene expression or enzyme accumulation, confirming that the observed effects on plastid isoprenoid levels in DXR-overexpressing lines were not an indirect consequence of altering DXS levels. The results indicate that the biosynthesis of MEP (the first committed intermediate of the pathway) limits the production of downstream isoprenoids in Arabidopsis chloroplasts, supporting a role for DXR in the control of the metabolic flux through the MEP pathway.