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Multi‐site genetic modulation of monolignol biosynthesis suggests new routes for formation of syringyl lignin and wall‐bound ferulic acid in alfalfa (Medicago sativa L.)

Multi‐site genetic modulation of monolignol biosynthesis suggests new routes for formation of... Genes encoding seven enzymes of the monolignol pathway were independently downregulated in alfalfa (Medicago sativa) using antisense and/or RNA interference. In each case, total flux into lignin was reduced, with the largest effects arising from the downregulation of earlier enzymes in the pathway. The downregulation of l‐phenylalanine ammonia‐lyase, 4‐coumarate 3‐hydroxylase, hydroxycinnamoyl CoA quinate/shikimate hydroxycinnamoyl transferase, ferulate 5‐hydroxylase or caffeic acid 3‐O‐methyltransferase resulted in compositional changes in lignin and wall‐bound hydroxycinnamic acids consistent with the current models of the monolignol pathway. However, downregulating caffeoyl CoA 3‐O‐methyltransferase neither reduced syringyl (S) lignin units nor wall‐bound ferulate, inconsistent with a role for this enzyme in 3‐O‐methylation ofS monolignol precursors and hydroxycinnamic acids. Paradoxically, lignin composition differed in plants downregulated in either cinnamate 4‐hydroxylase or phenylalanine ammonia‐lyase. No changes in the levels of acylated flavonoids were observed in the various transgenic lines. The current model for monolignol and ferulate biosynthesis appears to be an over‐simplification, at least in alfalfa, and additional enzymes may be needed for the 3‐O‐methylation reactions of S lignin and ferulate biosynthesis. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Plant Journal Wiley

Multi‐site genetic modulation of monolignol biosynthesis suggests new routes for formation of syringyl lignin and wall‐bound ferulic acid in alfalfa (Medicago sativa L.)

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References (58)

Publisher
Wiley
Copyright
Copyright © 2006 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0960-7412
eISSN
1365-313X
DOI
10.1111/j.1365-313X.2006.02857.x
pmid
16972868
Publisher site
See Article on Publisher Site

Abstract

Genes encoding seven enzymes of the monolignol pathway were independently downregulated in alfalfa (Medicago sativa) using antisense and/or RNA interference. In each case, total flux into lignin was reduced, with the largest effects arising from the downregulation of earlier enzymes in the pathway. The downregulation of l‐phenylalanine ammonia‐lyase, 4‐coumarate 3‐hydroxylase, hydroxycinnamoyl CoA quinate/shikimate hydroxycinnamoyl transferase, ferulate 5‐hydroxylase or caffeic acid 3‐O‐methyltransferase resulted in compositional changes in lignin and wall‐bound hydroxycinnamic acids consistent with the current models of the monolignol pathway. However, downregulating caffeoyl CoA 3‐O‐methyltransferase neither reduced syringyl (S) lignin units nor wall‐bound ferulate, inconsistent with a role for this enzyme in 3‐O‐methylation ofS monolignol precursors and hydroxycinnamic acids. Paradoxically, lignin composition differed in plants downregulated in either cinnamate 4‐hydroxylase or phenylalanine ammonia‐lyase. No changes in the levels of acylated flavonoids were observed in the various transgenic lines. The current model for monolignol and ferulate biosynthesis appears to be an over‐simplification, at least in alfalfa, and additional enzymes may be needed for the 3‐O‐methylation reactions of S lignin and ferulate biosynthesis.

Journal

The Plant JournalWiley

Published: Oct 1, 2006

Keywords: ; ; ; ;

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