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Among available super resolution techniques, STED (for STimulated Emission Depletion) scans the sample with two lasers: one for the excitation of the fluorescent probe located in the imaged sample, and a second one having a "doughnut" shape, called the depletion laser, whose role is to annihilate the emitting fluorescence around the excited area in the sample. Consequently, the spatial resolution becomes largely increased (until 50 nm for lateral resolution) in comparison to standard confocal imaging.

In order to validate this technique, STED imaging was performed on thin poplar sections previously incubated with a fluorescent probe made of a polyethylene glycol conjugated to a rhodamine fluorophore. This probe can interact with lignin that is present in secondary wall and this can reveal the presence of lignin. The comparison of standard confocal and STED images of the same sample shows an important gain in spatial resolution, which reveals fine details, in particular when a deconvolution process is applied to STED images. This opens new perspectives for topochemical analysis of plant cell walls at high resolution, without complex sample preparation, ideally complementing standard photon and electron microscopies.

Read: Paës G, Habrant A, Terryn C. Fluorescent nano-probes to image plant cell walls by super-resolution STED microscopy. Plants 2018; 7:11. DOI

Contact: Dr Gabriel Paës, gabriel.paes@inra.fr