Department of Metabolic Regulation, Faculty of Biology, University of Warsaw, Miecznikowa, Warsaw, Poland.
Department of Plant Anatomy and Cytology, Faculty of Biology, University of Warsaw, Miecznikowa, Warsaw, Poland.
J Exp Bot. 2019 Sep 24;70(18):4689-4704. doi: 10.1093/jxb/erz219.
The chloroplast thylakoid network is a dynamic structure which, through possible rearrangements, plays a crucial role in regulation of photosynthesis. Although the importance of the main components of the thylakoid membrane matrix, galactolipids, in the formation of the network of internal plastid membrane was found before, the structural role of monogalactosyldiacylglycerol (MGDG) and digalactosylidacylglycerol (DGDG) is still largely unknown. We elucidated detailed structural modifications of the thylakoid membrane system in Arabidopsis thaliana MGDG- and DGDG-deficient mutants. An altered MGDG/DGDG ratio was structurally reflected by formation of smaller grana, local changes in grana stacking repeat distance, and significant changes in the spatial organization of the thylakoid network compared with wild-type plants. The decrease of the MGDG level impaired the formation of the typical helical grana structure and resulted in a 'helical-dichotomic' arrangement. DGDG deficiency did not affect spatial grana organization but changed the shape of the thylakoid membrane network in situ from lens like into a flattened shape. Such structural disturbances were accompanied by altered composition of carotenoid and chlorophyll-protein complexes, which eventually led to the decreased photosynthetic efficiency of MGDG- and DGDG-deficient plants.
叶绿体类囊体网络是一个动态结构，通过可能的重排，在光合作用调节中起着至关重要的作用。虽然以前已经发现了类囊体膜基质的主要成分——半乳糖脂在内部质膜网络形成中的重要作用，但单半乳糖二酰基甘油（MGDG）和双半乳糖二酰基甘油（DGDG）的结构作用在很大程度上仍然未知。我们阐明了拟南芥 MGDG 和 DGDG 缺陷突变体中类囊体膜系统的详细结构修饰。MGDG/DGDG 比例的改变在结构上反映为形成较小的基粒，基粒堆叠重复距离的局部变化，以及与野生型植物相比，类囊体网络的空间组织发生了显著变化。MGDG 水平的降低会损害典型的螺旋基粒结构的形成，并导致“螺旋二分”排列。DGDG 缺乏并不影响空间基粒组织，但会改变类囊体膜网络在原位的形状，从透镜状变为扁平状。这种结构干扰伴随着类胡萝卜素和叶绿素-蛋白复合物组成的改变，最终导致 MGDG 和 DGDG 缺陷植物的光合作用效率降低。
