Engineering traditional monolignols out of lignin by concomitant up-regulation of F5H1 and down-regulation of COMT in Arabidopsis

Plant J. 2010 Dec;64(6):885-97. doi: 10.1111/j.1365-313X.2010.04353.x. Epub 2010 Oct 15.


Lignin engineering is a promising strategy to optimize lignocellulosic plant biomass for use as a renewable feedstock for agro-industrial applications. Current efforts focus on engineering lignin with monomers that are not normally incorporated into wild-type lignins. Here we describe an Arabidopsis line in which the lignin is derived to a major extent from a non-traditional monomer. The combination of mutation in the gene encoding caffeic acid O-methyltransferase (comt) with over-expression of ferulate 5-hydroxylase under the control of the cinnamate 4-hydroxylase promoter (C4H:F5H1) resulted in plants with a unique lignin comprising almost 92% benzodioxane units. In addition to biosynthesis of this particular lignin, the comt C4H:F5H1 plants revealed massive shifts in phenolic metabolism compared to the wild type. The structures of 38 metabolites that accumulated in comt C4H:F51 plants were resolved by mass spectral analyses, and were shown to derive from 5-hydroxy-substituted phenylpropanoids. These metabolites probably originate from passive metabolism via existing biochemical routes normally used for 5-methoxylated and 5-unsubstituted phenylpropanoids and from active detoxification by hexosylation. Transcripts of the phenylpropanoid biosynthesis pathway were highly up-regulated in comt C4H:F5H1 plants, indicating feedback regulation within the pathway. To investigate the role of flavonoids in the abnormal growth of comt C4H:F5H1 plants, a mutation in a gene encoding chalcone synthase (chs) was crossed in. The resulting comt C4H:F5H1 chs plants showed partial restoration of growth. However, a causal connection between flavonoid deficiency and this restoration of growth was not demonstrated; instead, genetic interactions between phenylpropanoid and flavonoid biosynthesis could explain the partial restoration. These genetic interactions must be taken into account in future cell-wall engineering strategies.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / enzymology
  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Down-Regulation
  • Gene Expression Regulation, Plant
  • Lignin / biosynthesis*
  • Methyltransferases / genetics
  • Methyltransferases / metabolism*
  • Mutation
  • Phenols / metabolism
  • Phenotype
  • Plants, Genetically Modified / enzymology
  • Plants, Genetically Modified / genetics
  • Promoter Regions, Genetic
  • Up-Regulation


  • Arabidopsis Proteins
  • Phenols
  • Lignin
  • Cytochrome P-450 Enzyme System
  • CYP84A1 protein, Arabidopsis
  • Methyltransferases
  • caffeate O-methyltransferase