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Sorghum mutant RG displays antithetic leaf shoot lignin accumulation resulting in improved stem saccharification properties.

Petti C, Harman-Ware AE, Tateno M, Kushwaha R, Shearer A, Downie AB, Crocker M, Debolt S - Biotechnol Biofuels (2013)

Bottom Line: Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed.Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves.Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Physiology, Department of Horticulture, Agricultural Science Center North, University of Kentucky, Lexington, KY 40546, USA. sdebo2@uky.edu.

ABSTRACT

Background: Improving saccharification efficiency in bioenergy crop species remains an important challenge. Here, we report the characterization of a Sorghum (Sorghum bicolor L.) mutant, named REDforGREEN (RG), as a bioenergy feedstock.

Results: It was found that RG displayed increased accumulation of lignin in leaves and depletion in the stems, antithetic to the trend observed in wild type. Consistent with these measurements, the RG leaf tissue displayed reduced saccharification efficiency whereas the stem saccharification efficiency increased relative to wild type. Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed. Similarities in cellulose content and structure by XRD-analysis support the correlation between increased saccharification properties and reduced lignin instead of changes in the cellulose composition and/or structure.

Conclusion: Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves. Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum.

No MeSH data available.


Saccharification and kinetic properties of RG and WT biomass. (A) Evaluation of saccharification property of RG and wild type tissue. Saccharification efficiency is expressed % cellulose converted to free glucose, as measured by YSI glucose analyzer (see Methods). Error bars are standard error from the mean of three biological and technical replicates. (B) Kinetic assessment of the digestibility of semi-purified cellulose in vitro. Cellulose from leaf and stem of both RG and wild type were evaluated by pseudo apparent Michaelis-Menten parameters to establish estimates for Km and Vmax. Error bars represent the standard error from the mean of three replicates.
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Figure 5: Saccharification and kinetic properties of RG and WT biomass. (A) Evaluation of saccharification property of RG and wild type tissue. Saccharification efficiency is expressed % cellulose converted to free glucose, as measured by YSI glucose analyzer (see Methods). Error bars are standard error from the mean of three biological and technical replicates. (B) Kinetic assessment of the digestibility of semi-purified cellulose in vitro. Cellulose from leaf and stem of both RG and wild type were evaluated by pseudo apparent Michaelis-Menten parameters to establish estimates for Km and Vmax. Error bars represent the standard error from the mean of three replicates.

Mentions: Based on the modified lignin content of the RG mutant, we sought to determine whether the lignocellulosic biomass displayed a different response to saccharification compared with wild type. It was anticipated that increased lignification in the leaves would influence saccharification efficiency. Indeed, it was found that WT leaves were more efficiently converted to fermentable sugars than RG leaves (Figure 5A). These data are consistent with the increased lignin content of RG leaves reducing digestibility. In the stems of the RG mutant, where lower insoluble lignin was quantified (Figure 4E), we observed that the RG mutant displayed higher saccharification efficiency than WT. This too supports lignin content having an influence on digestibility. Secondly, these data are consistent with the RG mutant phenotype being a suitable marker for digestibility traits in a tissue specific manner. As a general result, the leaves of both WT and RG were enzymatically deconstructed more efficiently than stems (Figure 5A).


Sorghum mutant RG displays antithetic leaf shoot lignin accumulation resulting in improved stem saccharification properties.

Petti C, Harman-Ware AE, Tateno M, Kushwaha R, Shearer A, Downie AB, Crocker M, Debolt S - Biotechnol Biofuels (2013)

Saccharification and kinetic properties of RG and WT biomass. (A) Evaluation of saccharification property of RG and wild type tissue. Saccharification efficiency is expressed % cellulose converted to free glucose, as measured by YSI glucose analyzer (see Methods). Error bars are standard error from the mean of three biological and technical replicates. (B) Kinetic assessment of the digestibility of semi-purified cellulose in vitro. Cellulose from leaf and stem of both RG and wild type were evaluated by pseudo apparent Michaelis-Menten parameters to establish estimates for Km and Vmax. Error bars represent the standard error from the mean of three replicates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852544&req=5

Figure 5: Saccharification and kinetic properties of RG and WT biomass. (A) Evaluation of saccharification property of RG and wild type tissue. Saccharification efficiency is expressed % cellulose converted to free glucose, as measured by YSI glucose analyzer (see Methods). Error bars are standard error from the mean of three biological and technical replicates. (B) Kinetic assessment of the digestibility of semi-purified cellulose in vitro. Cellulose from leaf and stem of both RG and wild type were evaluated by pseudo apparent Michaelis-Menten parameters to establish estimates for Km and Vmax. Error bars represent the standard error from the mean of three replicates.
Mentions: Based on the modified lignin content of the RG mutant, we sought to determine whether the lignocellulosic biomass displayed a different response to saccharification compared with wild type. It was anticipated that increased lignification in the leaves would influence saccharification efficiency. Indeed, it was found that WT leaves were more efficiently converted to fermentable sugars than RG leaves (Figure 5A). These data are consistent with the increased lignin content of RG leaves reducing digestibility. In the stems of the RG mutant, where lower insoluble lignin was quantified (Figure 4E), we observed that the RG mutant displayed higher saccharification efficiency than WT. This too supports lignin content having an influence on digestibility. Secondly, these data are consistent with the RG mutant phenotype being a suitable marker for digestibility traits in a tissue specific manner. As a general result, the leaves of both WT and RG were enzymatically deconstructed more efficiently than stems (Figure 5A).

Bottom Line: Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed.Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves.Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum.

View Article: PubMed Central - HTML - PubMed

Affiliation: Plant Physiology, Department of Horticulture, Agricultural Science Center North, University of Kentucky, Lexington, KY 40546, USA. sdebo2@uky.edu.

ABSTRACT

Background: Improving saccharification efficiency in bioenergy crop species remains an important challenge. Here, we report the characterization of a Sorghum (Sorghum bicolor L.) mutant, named REDforGREEN (RG), as a bioenergy feedstock.

Results: It was found that RG displayed increased accumulation of lignin in leaves and depletion in the stems, antithetic to the trend observed in wild type. Consistent with these measurements, the RG leaf tissue displayed reduced saccharification efficiency whereas the stem saccharification efficiency increased relative to wild type. Reduced lignin was linked to improved saccharification in RG stems, but a chemical shift to greater S:G ratios in RG stem lignin was also observed. Similarities in cellulose content and structure by XRD-analysis support the correlation between increased saccharification properties and reduced lignin instead of changes in the cellulose composition and/or structure.

Conclusion: Antithetic lignin accumulation was observed in the RG mutant leaf-and stem-tissue, which resulted in greater saccharification efficiency in the RG stem and differential thermochemical product yield in high lignin leaves. Thus, the red leaf coloration of the RG mutant represents a potential marker for improved conversion of stem cellulose to fermentable sugars in the C4 grass Sorghum.

No MeSH data available.