ROOT-ExM: Super-Resolution Imaging of Proteins in Arabidopsis Roots by Expansion Microscopy

Area of Science:

• Plant Biology
• Microscopy Techniques
• Cellular Imaging

Background:

• Light microscopy is limited by diffraction, hindering nanoscale biomolecule visualization.
• Expansion microscopy (ExM) overcomes resolution limits by physically expanding specimens.
• Applying ExM to plant tissues is challenging due to rigid cell walls and multicellularity.

Purpose of the Study:

• To develop and optimize an Expansion Microscopy (ExM) protocol for Arabidopsis thaliana root tissues.
• To enable super-resolution imaging of plant cells without specialized hardware.
• To facilitate detailed structural analysis of plant cell ultrastructure.

Main Methods:

• Developed a robust ExM protocol for Arabidopsis roots, including critical steps like immunostaining, anchoring, gelation, denaturation, and cell wall digestion.
• Achieved specimen expansion using a swellable hydrogel system.
• Utilized standard confocal microscopy for imaging.

Main Results:

• The protocol achieved an approximate 4.3× expansion factor for Arabidopsis root tissues.
• Enabled an effective lateral resolution of approximately 60 nm.
• Successfully visualized microtubules with preserved ultrastructure in 3D.
• Demonstrated deep-tissue imaging capabilities.

Conclusions:

• This optimized ExM protocol overcomes challenges in plant tissue expansion, enabling super-resolution imaging.
• Provides an accessible method for plant researchers to achieve nanoscale resolution using standard microscopy.
• Facilitates detailed structural and ultrastructural analysis of plant cells and tissues.