photobleaching-enables-super-resolution-imaging-ftsz-ring

Photobleaching Enables Super-resolution Imaging of the FtsZ Ring in the Cyanobacterium <em>Prochlorococcus</em>

Super-resolution microscopy has been widely used to study protein interactions and subcellular structures in many organisms. In photosynthetic organisms, ...

Hong Kong University of Science and Technology

Superresolution imaging has revealed subcellular structures and protein interactions in many organisms. However, superresolution microscopy with lateral resolution better than 100 nm has not been achieved in photosynthetic cells due to the interference of a high-autofluorescence background. Here, we developed a photobleaching method to effectively reduce the autofluorescence of cyanobacterial and plant cells. We achieved lateral resolution of ~10 nm with stochastic optical reconstruction microscopy (STORM) in the sphere-shaped cyanobacterium  and the flowering plant  During the cell cycle of , we characterized the three-dimensional (3D) organization of the cell division protein FtsZ, which forms a ring structure at the division site and is important for cytokinesis of bacteria and chloroplasts. Although the FtsZ ring assembly process in rod-shaped bacteria has been studied extensively, it has rarely been studied in sphere-shaped bacteria. Similarly to rod-shaped bacteria, our results with  also showed the assembly of FtsZ clusters into incomplete rings and then complete rings during cell division. Differently from rod-shaped bacteria, the FtsZ ring diameter was not found to decrease during  cell division. We also discovered a novel double-Z-ring structure, which may be the Z rings of two daughter cells in a predivisional mother cell. Our results showed a quantitative picture of the  Z ring organization of sphere-shaped bacteria. Superresolution microscopy has not been widely used to study photosynthetic cells due to their high-autofluorescence background. Here, we developed a photobleaching method to reduce the autofluorescence of cyanobacteria and plant cells. After photobleaching, we performed superresolution imaging in the cyanobacterium  and the flowering plant  with ~10-nm resolution, which is the highest resolution in a photosynthetic cell. With this method, we characterized the 3D organization of the cell division protein FtsZ in  We found that the morphological variation of the FtsZ ring during cell division of the sphere-shaped cyanobacterium  is similar but not identical to that of rod-shaped bacteria. Our method might also be applicable to other photosynthetic organisms.

Yaxin Liu

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