期刊
BIOENERGY RESEARCH
卷 2, 期 4, 页码 198-208出版社
SPRINGER
DOI: 10.1007/s12155-009-9056-8
关键词
Alfalfa; Gene down-regulation; Lignin structure; NMR; p-Hydroxyphenyl; Methoxyl; beta-O-4 linkage
资金
- Office of Biological and Environmental Research in the DOE Office of Science
- DOE Office of Biological and Environmental Research through the BioEnergy Science Center [DE-AC05-00OR22725]
Independent down-regulation of genes encoding p-coumarate 3-hydroxylase (C3H) and hydroxycinnamoyl CoA:shikimate/quinate hydroxycinnamoyl transferase (HCT) has been previously shown to reduce the recalcitrance of alfalfa and thereby improve the release of fermentable sugars during enzymatic hydrolysis. In this study, ball-milled lignins were isolated from wild-type control, C3H, and HCT gene down-regulated alfalfa plants. One-and two-dimensional nuclear magnetic resonance (NMR) techniques were utilized to determine structural changes in the ball-milled alfalfa lignins resulting from this genetic engineering. After C3H and HCT gene down-regulation, significant structural changes had occurred to the alfalfa ball-milled lignins compared to the wild-type control. A substantial increase in p-hydroxyphenyl units was observed in the transgenic alfalfa ball-milled lignins as well as a concomitant decrease in guaiacyl and syringyl units. Two-dimensional C-13-H-1 heteronuclear single quantum coherence correlation NMR, one-dimensional distortionless enhancement by polarization transfer-135, and C-13 NMR measurement showed a noteworthy decrease in methoxyl group and beta-O-4 linkage contents in these transgenic alfalfa lignins. C-13 NMR analysis estimated that C3H gene down-regulation reduced the methoxyl content by similar to 55-58% in the ball-milled lignin, while HCT down-regulation decreased methoxyl content by similar to 73%. The gene down-regulated C3H and HCT transgenic alfalfa lignin was largely a p-hydroxyphenyl (H) rich type lignin. Compared to the wild-type plant, the C3H and HCT transgenic lines had an increase in relative abundance of phenylcoumaran and resinol in the ball-milled lignins.
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