Fluorescent Nano-Probes to Image Plant Cell Walls by Super-Resolution STED Microscopy

Abstract

Lignocellulosic biomass is a complex network of polymers making up the cell walls of plants. It represents a feedstock of sustainable resources to be converted into fuels, chemicals, and materials. Because of its complex architecture, lignocellulose is a recalcitrant material that requires some pretreatments and several types of catalysts to be transformed efficiently. Gaining more knowledge in the architecture of plant cell walls is therefore important to understand and optimize transformation processes. For the first time, super-resolution imaging of poplar wood samples has been performed using the Stimulated Emission Depletion (STED) technique. In comparison to standard confocal images, STED reveals new details in cell wall structure, allowing the identification of secondary walls and middle lamella with fine details, while keeping open the possibility to perform topochemistry by the use of relevant fluorescent nano-probes. In particular, the deconvolution of STED images increases the signal-to-noise ratio so that images become very well defined. The obtained results show that the STED super-resolution technique can be easily implemented by using cheap commercial fluorescent rhodamine-PEG nano-probes which outline the architecture of plant cell walls due to their interaction with lignin. Moreover, the sample preparation only requires easily-prepared plant sections of a few tens of micrometers, in addition to an easily-implemented post-treatment of images. Overall, the STED super-resolution technique in combination with a variety of nano-probes can provide a new vision of plant cell wall imaging by filling in the gap between classical photon microscopy and electron microscopy.

Plant phenotyping relevance

植物細胞壁の構造を可視化・抽出する超解像STED画像法と蛍光ナノプローブを中心に開発・実証しており、植物形態特性の取得方法が主題である。

Code and data availability

The paper reports STED/confocal imaging of poplar wood sections with a PEG-rhodamine probe. The only public link is the MDPI supplementary file, which per the text contains only 'Figure S1: Autofluorescence contour map of PEG-R probe' — a single spectral figure, not the paper's microscopy images, phenotype measurements

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