The second with the introduction of the electron microscope and the parallel development of improved specimen preparation methods. The first phase of chloroplast structure research coincided with the development of new light microscopes with better lenses. This has also been the case for investigations of the architecture of higher plant chloroplast membranes, where the introduction of new and better microscopes and analytical methods has improved the spatial resolution by ×5000, from ~ 1.0 μm to ~ 0.2 nm. Throughout history the introduction of new research techniques has led to significant advances in scientific knowledge. These investigations have provided novel insights into thylakoid architecture and plastoglobules (summarized in a new thylakoid model), while also producing molecular-scale views of grana and stroma thylakoids in which individual functional complexes can be identified. The last section (2000–2020) focuses on the most recent discoveries made possible by atomic force microscopy of hydrated membranes, and electron tomography and cryo-electron tomography of cryofixed thylakoids. Freeze-fracture and freeze-etch methods verified the helical nature of the stroma thylakoids, while also providing precise information on how the electron transport chain and ATP synthase complexes are non-randomly distributed between grana and stroma membrane regions. When the stroma thylakoids were shown to spiral around the grana stacks as multiple right-handed helices, it was confirmed that the membranes of a chloroplast are all interconnected. The development of the transmission electron microscope (1940–2000) and thin sectioning techniques demonstrated that grana consist of stacks of closely appressed grana thylakoids interconnected by non-appressed stroma thylakoids. More recent (1990–2020) chloroplast dynamic studies have benefited from laser confocal and 3D-structured illumination microscopy. This review is organized into three chronological sections: During the classic light microscope period (1678–1940), the development of improved microscopes led to the identification of green grana, a colorless stroma, and a membrane envelope. Since then, microscopic studies have continued to contribute critical insights into the complex architecture of chloroplast membranes and how their structure relates to function. Microscopic studies of chloroplasts can be traced back to the year 1678 when Antonie van Leeuwenhoek reported to the Royal Society in London that he saw green globules in grass leaf cells with his single-lens microscope.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |