Super-resolution expansion microscopy in plant roots

Super-resolution methods enable spatial resolution far better than the optical diffraction limit of about half the wavelength of light (∼200-300 nm) but have yet to attain widespread use in plants, owing in large part to plants’ challenging optical properties. Expansion microscopy improves effective resolution by isotropically increasing physical distances between sample structures while preserving relative spatial arrangements, and clears the sample. However, its application to plants has been hindered by the rigid, mechanically cohesive structure of plant tissues. Here, we report on whole-mount expansion microscopy of Arabidopsis thaliana root tissues (PlantEx), achieving 4-fold resolution increase over conventional microscopy, highlighting microtubule cytoskeleton organization and interaction between molecularly defined cellular constituents. By combining PlantEx with STED microscopy, we increase nanoscale resolution further and visualize the complex organization of subcellular organelles from intact tissues by example of the densely packed COPI-coated vesicles associated with the Golgi apparatus and put these into cellular structural context.