Abstract
The primary plant cell wall is a complex matrix composed of interconnected polysaccharides including cellulose, hemicellulose, and pectin. Changes of this dynamic polysaccharide system play a critical role during plant cell development and differentiation. A better understanding of cell wall architectures can provide insight into the plant cell development. In this study, a Raman spectroscopic imaging approach was developed to visualize the distribution of plant cell wall polysaccharides. In this approach, Surface-enhanced Raman scattering (SERS through self-assembled silver nanoparticles) was combined with Raman labels (4-Aminothiophenol. 4ATP) and targeted enzymatic hydrolysis to improve the sensitivity, specificity, and throughput of the Raman imaging technique, and to reveal the distribution of pectin and its co-localization with xyloglucan inside onion epidermal cell (OEC) wall. This technique significantly decreased the required spectral acquisition time. The resulted Raman spectra showed a high Raman signal. The resulted Raman images successfully revealed and characterized the pectin distribution and its co-localization pattern with xyloglucan in OEC wall.
Highlights
Polysaccharides are the main components of the plant cell wall
The sequential EPG treatment caused the Raman intensity to significantly decrease at the cell corner, the out layer of the cell wall that connects to the middle lamella area and middle lamella area, the locations of higher accumulation of pectins according to our results shown in Fig 5g, whereas no much change was observed at the cell inner surface
A novel Raman chemical imaging method was developed to employ Surface-enhanced Raman scattering (SERS) imaging to characterize polysaccharide distribution and organization in onion epidermal cell wall. The utilization of this new method to visualize polysaccharide distribution was assisted by the application of highly specific glycosyl hydrolases to degrade hemicellulose and pectin molecules in cell wall in situ
Summary
Polysaccharides are the main components of the plant cell wall. The complex network of polysaccharides consists of cellulose, hemicelluloses and pectin [1]. Cellulose is a linear unbranched polysaccharide formed of β-1-4-D-Glucose residuals. Hemicellulose is a group of heterogeneous polysaccharides that have β-(1,4)-linked backbones of various base units. Pectin is a group of complex polysaccharides formed with α-(1,4)-D-galacluronic acid residuals. The α-(1,4)-D-galacturonic acid is a unique monosaccharide due to its carboxylic group ester. 70% of pectin is comprised of α-(1,4)-D-galacturonic acid residues [2]. Some side chains of hemicelluloses and plant cell wall proteins contain a limited number of carboxylic groups as well. The main polysaccharides in the pectin group include homogalacturonan
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