Galactolipid synthesis in chloroplast inner envelope is essential for proper thylakoid biogenesis, photosynthesis, and embryogenesis
Galactolipid synthesis in chloroplast inner envelope is essential for proper thylakoid biogenesis, photosynthesis, and embryogenesis
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DOI：
10.1073/pnas.0704680104
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发表时间：
2007-10-23
影响因子：
11.1
通讯作者：
Ohta, Hiroyuki
中科院分区：
文献类型：
--
作者：
Kobayashi, Koichi;Kondo, Maki;Ohta, Hiroyuki
类囊体膜的生物发生是植物光自养生长不可缺少的事件，它需要显著增加类囊体膜脂类单半乳糖二酰甘油(MGDG)的水平，它构成了叶绿体中大量的膜脂。MGDG生物合成的最后一步发生在叶绿体被膜中，并由MGDG合成酶催化。在这里，我们报告了一个在MGDG合成酶1中完全缺失的拟南芥突变体的鉴定和鉴定。突变体种子只有在蔗糖存在的情况下才能萌发成小白化。幼苗缺乏半乳糖脂，并破坏了光合膜，导致光合作用能力和光自养生长完全受损。此外，在突变体中观察到了在成熟的WT叶绿体中没有的内陷现象，这支持了一个古老的假说，即内陷是叶绿体早期生物发生中的一个主要事件。除了有缺陷的幼苗表型外，突变体中的胚胎发育也停止了，尽管带有受损胚胎的种子可以异养萌发。这些结果证明了半乳糖脂不仅在光合作用生长中的重要性，而且在胚胎发育中也是重要的。
The biogenesis of thylakoid membranes, an indispensable event for the photoautotrophic growth of plants, requires a significant increase in the level of the unique thylakoid membrane lipid monogalactosyldiacylglycerol (MGDG), which constitutes the bulk of membrane lipids in chloroplasts. The final step in MGDG biosynthesis occurs in the plastid envelope and is catalyzed by MGDG synthase. Here we report the identification and characterization of an Arabidopsis mutant showing a complete defect in MGDG synthase 1. The mutant seeds germinated as small albinos only in the presence of sucrose. The seedlings lacked galactolipids and had disrupted photosynthetic membranes, leading to the complete impairment of photosynthetic ability and photoautotrophic growth. Moreover, invagination of the inner envelope, which is not seen in mature WT chloroplasts, was observed in the mutant, supporting an old hypothesis that envelope invagination is a major event in early chloroplast biogenesis. In addition to the defective seedling phenotype, embryo development was arrested in the mutant, although seeds with impaired embryos could germinate heterotrophically. These results demonstrate the importance of galactolipids not only in photosynthetic growth but also in embryogenesis.