Schwender J, Gemünden C, Lichtenthaler H K
Botanisches Institut, Lehrstuhl II, Universität Karlsruhe, Germany.
Planta. 2001 Feb;212(3):416-23. doi: 10.1007/s004250000409.
The biosynthesis of the C5 building block of isoprenoids, isopentenyl diphosphate (IPP), proceeds in higher plants via two basically different pathways; in the cytosolic compartment sterols are formed via mevalonate (MVA), whereas in the plastids the isoprenoids are formed via the 1-deoxyxylulose 5-phosphate/2-C-methylerythritol 4-phosphate pathway (DOXP/MEP pathway). In the present investigation, we found for the Charophyceae, being close relatives to land plants, and in the original green flagellate Mesostignma virilde the same IPP biosynthesis pattern as in higher plants: sterols are formed via MVA, and the phytol-moiety of chlorophylls via the DOXP/MEP pathway. In contrast, representatives of four classes of the Chlorophyta (Chlorophyceae, Ulvophyceae, Trebouxiophyceae, Prasinophyceae) did not incorporate MVA into sterols or phytol. Instead, they incorporated [1-2H1]-1-deoxy-D-xylulose into phytol and sterols. The results indicate that the entire Chlorophyta lineage, which is well separated from the land plant/Charophyceae lineage, is devoid of the acetate/ MVA pathway and uses the DOXP/MEP pathway not only for plastidic, but also for cytosolic isoprenoid formation.
类异戊二烯的C5构建单元异戊烯基二磷酸（IPP）在高等植物中的生物合成通过两条基本不同的途径进行；在胞质区室中，固醇通过甲羟戊酸（MVA）形成，而在质体中，类异戊二烯通过1-脱氧木酮糖5-磷酸/2-C-甲基赤藓糖醇4-磷酸途径（DOXP/MEP途径）形成。在本研究中，我们发现与陆地植物亲缘关系较近的轮藻以及原始绿鞭毛藻Mesostignma virilde具有与高等植物相同的IPP生物合成模式：固醇通过MVA形成，叶绿素的叶绿醇部分通过DOXP/MEP途径形成。相比之下，绿藻门四个纲（绿藻纲、石莼纲、小球藻纲、原绿藻纲）的代表物种并未将MVA掺入固醇或叶绿醇中。相反，它们将[1-2H1]-1-脱氧-D-木酮糖掺入叶绿醇和固醇中。结果表明，与陆地植物/轮藻谱系完全分离的整个绿藻谱系缺乏乙酸/MVA途径，并且不仅将DOXP/MEP途径用于质体类异戊二烯的形成，还用于胞质类异戊二烯的形成。
