There’s only so much you can do with a microscope, before you need something bigger and more expensive. A technique developed by Kevin Cox & colleagues provides better views – but you don’t get a bigger microscope. The technique, called ExPOSE, is a form of expansion microscopy.
Expansion microscopy (ExM) physically enlarges biological tissues by embedding them in hydrogel. Scientists anchor cellular components to this polymer using chemical linkers. Add water, and the hydrogel absorbs it, swelling uniformly in all directions, and separates the cellular components.
Workflow for expansion of plant protoplast systems (ExPOSE). Cox et al 2025.
As the hydrogel swells, so do the cellular structures, making tiny details easier to see under a standard microscope. This technique works fine with animal cells, but plant cells have always been more difficult, because they have something that animal cells don’t.
Plants have rigid cell walls that prevent uniform expansion, so it wasn’t possible to use ExM well with them. Cox & colleagues’ solution is simple: you use protoplasts instead of cells. These are plant cells with their walls removed. The resulting cell-lite can expand by up to 10 times.
ExPOSE reveals subcellular details impossible to see with conventional microscopy such as individual actin filaments and internal mitochondrial structures. But there’s a claim in the paper that is even more striking, you can even see the messages cells use. They say:
Sample cells under the microscope. I'm not a cell biologist, so sadly I can't really provide anything that would be a more helpful description.
Expansion of plant protoplast systems (ExPOSE) enhances detection of CAB1mRNA foci in protoplasts. Cox et al. 2025
“Overall, our results demonstrate the high sensitivity and compatibility that ExPOSE, in combination with HCR and lattice SIM, provides in revealing the fine detail of individual mRNA foci localization in single-cell protoplasts.”
What makes ExPOSE especially valuable is that by working with protoplasts, the technique bypasses many of these species-specific complications. Cox and colleagues have applied the technique to Arabidopsis, maize and duckweed. Cox says that understanding duckweed could be particularly useful.
“Because duckweed is so small, it gives us a model to understand what every cell is doing at a given moment,’ Cox says. This is particularly useful when studying how plant cells respond to stress, such as infections or environmental changes.
The research has important implications for agriculture. Seeing exactly how plant cells communicate during infections could help develop crops that better withstand diseases without excessive pesticide use, improving environmental sustainability.
Cox, K.L., Pardi, S.A., O’Connor, L., Klebanovych, A., Huss, D., Nusinow, D.A., Meyers, B.C., & Czymmek, K.J. (2025). ExPOSE: a comprehensive toolkit to perform expansion microscopy in plant protoplast systems. The Plant Journal, 121, e70049. https://doi.org/n96c
Cross-posted to Bluesky & Mastodon.
Cover Image: Canva. Other images: Cox et al 2026.
You can follow Kevin Cox at @kcox-bioguy.bsky.social
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