Max Planck Institute for Chemical Ecology, Department of Biochemistry, Hans-Knöll-Strasse 8, D-07745 Jena, Germany.
Max Planck Institute for Chemical Ecology, Department of Biochemistry, Hans-Knöll-Strasse 8, D-07745 Jena, Germany.
Phytochemistry. 2014 Feb;98:110-9. doi: 10.1016/j.phytochem.2013.11.010. Epub 2013 Dec 17.
In higher plants, both the methylerythritol phosphate (MEP) and mevalonate (MVA) pathways contribute to the biosynthesis of isoprenoids. However, despite a significant amount of research on the activity of these pathways under different conditions, the relative contribution of each to the biosynthesis of diverse isoprenoids remains unclear. In this work, we examined the formation of several classes of isoprenoids in cotton (Gossypium hirsutum L.). After feeding [5,5-(2)H2]-1-deoxy-D-xylulose ([5,5-(2)H2]DOX) and [2-(13)C]MVA to intact cotton seedlings hydroponically, incorporation into isoprenoids was analyzed by MS and NMR. The predominant pattern of incorporation followed the classical scheme in which C5 units from the MEP pathway were used to form monoterpenes (C10), phytol side chains (C20) and carotenoids (C40) while C5 units from the MVA pathway were used to form sesquiterpenes (C15), terpenoid aldehydes (C15 and C25) and steroids/triterpenoids (C30). However, both pathways contributed to all classes of terpenoids, sometimes substantially. For example, the MEP pathway provided up to 20% of the substrate for sterols and the MVA pathway provided as much as 50% of the substrate for phytol side chains and carotenoids. Incorporation of C5 units from the MEP pathway was highest in cotyledons, compared to true leaves, and not observed at all in the roots. Incorporation of C5 units from the MVA pathway was highest in the roots (into sterols) and more prominent in the first true leaves than in other above-ground organs. The relative accumulation of label in intermediates vs. end products of phytosterol metabolism confirmed previous identification of slow steps in this pathway.
在高等植物中，甲基赤藓醇磷酸（MEP）和甲羟戊酸（MVA）途径都有助于异戊二烯的生物合成。然而，尽管对这些途径在不同条件下的活性进行了大量研究，但每个途径对不同异戊二烯生物合成的相对贡献仍不清楚。在这项工作中，我们研究了棉花（Gossypium hirsutum L.）中几种类异戊二烯的形成。在水培条件下，用[5,5-(2)H2]-1-脱氧-D-木酮糖([5,5-(2)H2]DOX)和[2-(13)C]MVA 处理完整的棉花幼苗后，通过 MS 和 NMR 分析异戊二烯的掺入情况。掺入的主要模式遵循经典模式，其中 MEP 途径的 C5 单位用于形成单萜（C10）、植醇侧链（C20）和类胡萝卜素（C40），而 MVA 途径的 C5 单位用于形成倍半萜（C15）、萜烯醛（C15 和 C25）和甾体/三萜（C30）。然而，两条途径都为所有类别的萜烯提供了贡献，有时甚至是主要的贡献。例如，MEP 途径为甾醇提供了高达 20%的底物，MVA 途径为植醇侧链和类胡萝卜素提供了高达 50%的底物。与真叶相比，C5 单位从 MEP 途径的掺入在子叶中最高，而在根中则完全没有。C5 单位从 MVA 途径的掺入在根中最高（进入甾醇），在第一片真叶中比在其他地上器官中更为明显。植固醇代谢中间产物与终产物之间标记物的相对积累证实了该途径中存在缓慢步骤。
