Biology Reference
In-Depth Information
Fig. 7. Impact of CAD suppression on monolignol biosynthesis in P. radiata.
CAD suppression restricted the biosynthesis of p-coumaryl alcohol and coniferyl
alcohol (dashed arrows) and promoted the biosynthesis of dihydro-p-coumaryl alco-
hol and dihydroconiferyl alcohol (bold). Proposed biosynthetic pathway for the
production of dihydro-p-coumaryl alcohol and dihydroconiferyl alcohol in pine
CAD-RNAi lines is indicated; PPDBR, phenylpropenal double bond reductase; ?,
unknown dehydrogenase.
growth and fitness (
Wadenb¨ck et al., 2008; Wagner et al., 2009
, unpublished
results). As it therefore seems difficult to facilitate processing of lignocellu-
losic material by successfully reducing lignin content in conifers, other stra-
tegies might have to be entertained.
The difficulty of processing lignocellulosic material from conifers is at least
partly due to the more 'condensed' structure of conifer lignin. p-Coumaryl
alcohol and coniferyl alcohol, the principal building blocks of conifer lignin,
enable covalent linkages to (and between) aromatic ring 3- and 5-positions,
which results in a more condensed form of lignin than that typically found in
hardwoods (
Brunow and Lundquist, 2010
). Changing the monomeric lignin
composition in conifers without altering lignin content represents an alterna-
tive approach toward improving processing of conifer biomass. Recombinant
experiments in pine have already shown that non-traditional monolignols
can be incorporated into the lignin polymer (
Wagner et al.,2011
). It might
