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In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy

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ABSTRACT

Background: Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials.

Results: Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have proven to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall.

Conclusion: We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. We believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.

Electronic supplementary material: The online version of this article (doi:10.1186/s13068-016-0669-9) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

In situ 3D SRS imaging to track xylan distribution in deacetylated corn stover cell wall before and after xylan digestion. a–d Before digestion. a′–d′ The same cell wall regions in a–d after xylanases digestion for comparison. Xylan Raman frequency at 1471 cm−1 was chosen for SRS imaging. a, b, a′, b′ cell corner; c, d, c′, d′cell wall between two cell corners
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Fig7: In situ 3D SRS imaging to track xylan distribution in deacetylated corn stover cell wall before and after xylan digestion. a–d Before digestion. a′–d′ The same cell wall regions in a–d after xylanases digestion for comparison. Xylan Raman frequency at 1471 cm−1 was chosen for SRS imaging. a, b, a′, b′ cell corner; c, d, c′, d′cell wall between two cell corners

Mentions: More striking xylanases-induced change in xylan distribution can be revealed by the in situ 3D SRS imaging of xylan in the same cell wall region following xylanases digestion. Figure 7 compares the 3D reconstructions of xylan’s SRS signal at 1471 cm−1 before and after xylanases digestion. Xylan concentration as reflected by its SRS signal intensity clearly diminishes from cell lumen towards cell corner, whereas the remaining xylan is more located at cell corners. This 3D imaging technique could be useful for tracking xylan change under more complicate chemical/biological treatment conditions.Fig. 7


In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy
In situ 3D SRS imaging to track xylan distribution in deacetylated corn stover cell wall before and after xylan digestion. a–d Before digestion. a′–d′ The same cell wall regions in a–d after xylanases digestion for comparison. Xylan Raman frequency at 1471 cm−1 was chosen for SRS imaging. a, b, a′, b′ cell corner; c, d, c′, d′cell wall between two cell corners
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5120481&req=5

Fig7: In situ 3D SRS imaging to track xylan distribution in deacetylated corn stover cell wall before and after xylan digestion. a–d Before digestion. a′–d′ The same cell wall regions in a–d after xylanases digestion for comparison. Xylan Raman frequency at 1471 cm−1 was chosen for SRS imaging. a, b, a′, b′ cell corner; c, d, c′, d′cell wall between two cell corners
Mentions: More striking xylanases-induced change in xylan distribution can be revealed by the in situ 3D SRS imaging of xylan in the same cell wall region following xylanases digestion. Figure 7 compares the 3D reconstructions of xylan’s SRS signal at 1471 cm−1 before and after xylanases digestion. Xylan concentration as reflected by its SRS signal intensity clearly diminishes from cell lumen towards cell corner, whereas the remaining xylan is more located at cell corners. This 3D imaging technique could be useful for tracking xylan change under more complicate chemical/biological treatment conditions.Fig. 7

View Article: PubMed Central - PubMed

ABSTRACT

Background: Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials.

Results: Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have proven to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall.

Conclusion: We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. We believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.

Electronic supplementary material: The online version of this article (doi:10.1186/s13068-016-0669-9) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus