1. BRC Science Highlight
Suppression of the lignin biosynthetic gene CCR1 results in decreased lignin recalcitrance and increased digestibility
Objective In this study, we examined features of a lignin biosynthetic mutant in maize that we hypothesized could result in an increase in the levels of more readily cleavable ester bonds in the lignin backbone (“zip-lignin”).
Approach
Analyze a maize ccr1 insertion mutant for CCR transcript level, plant growth and development, total lignin content, monolignol ferulate (zip-lignin) levels, and release of glucose and xylose.
Results/Impacts
Maize ccr1 mutant plants, in comparison to wild-type plants, have reduced total lignin levels, normal growth and development, increased zip-lignin levels, and increased digestibility as measured by glucose and xylose release.
The increased monolignol ferulate incorporation into lignins (i.e., higher zip-lignin levels) in ccr1 mutant maize plants suggests that downregulation of CCR may be a viable biosynthetic strategy for increasing zip levels in other biofuel crops as well.
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An abbreviated version of the lignin biosynthetic pathways highlighting the effects of the ccr1 mutation. The mutated CCR1 gene results in reduced CCR1 transcript, and presumably less CCR1 enzyme, and a pool of feruloyl-CoA (FA reservoir). The conjugates formed between the monolignols and feruloyl-CoA by ZmFMT are incorporated into the lignin polymer, generating a zip-lignin in which the ester bonds in the backbone are readily cleaved by base.
Smith, R. A. et al. “Suppression of CINNAMOYL-CoA REDUCTASE increases the level of monolignol ferulates incorporated into maize lignins.” Biotechnology for Biofuels 10, 109 (2017) [DOI: /s ].
GLBRC May 2017