Biology Reference
In-Depth Information
Fig. 2. Biosynthesis of monolignols in conifers starting with
L
-phenylalanine.
PAL,
L
-phenylalanine ammonia-lyase; 4CL, 4-coumarate-CoA ligase; HCT,
p-hydroxycinnamoyl-CoA shikimate hydroxycinnamoyl transferase; C3H,
p-coumarate 3-hydroxylase; CCoAOMT, caffeoyl-CoA O-methyl transferase;
CCR, cinnamoyl-CoA reductase; CAD, cinnamyl alcohol dehydrogenase.
4CL suppression in pine plants resulted in an up to 50% reduction in lignin
content and plants with a dwarfed phenotype and reduced wood stiffness
(
Wagner et al., 2009
). Tracheids in 4CL-RNAi plants displayed reduced
levels of lignification and signs of collapse, clearly demonstrating that conifer
plants cannot tolerate substantial reductions in lignin content. Interestingly,
lignification in tracheids adjacent to resin canals and wood rays were least
affected by 4CL suppression. It could be speculated that cells within resin
canals and wood rays were able to complement the diminished monolignol
supply in such tracheids (
Wagner et al., 2009
).
