Biology Reference
In-Depth Information
Fig. 3. Impact of 4CL suppression on monolignol biosynthesis in P. radiata. 4CL
suppression restricted the biosynthesis of coniferyl alcohol (dashed arrows) and to a
lesser extent p-coumaryl alcohol and promoted the biosynthesis of bark-related
compounds such as flavonoids (bold); ?: unknown flavonoid-specific 4CL.
such a substantial stimulation of bark formation. Suppression of 4CL in pine
plants must therefore have impacted many genes other than 4CL,andin
particular those involved in the formation of flavonoids and flavonoid-derived
polymers such as tannins, which are needed for bark formation.
2. Suppression of hydroxycinnamoyl-CoA:shikimate
hydroxycinnamoyl transferase
Hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl transferase (HCT) is
essential for the production of G-lignin in conifers (
Wagner et al., 2007
) and
the biosynthesis of both G- and S-lignin in angiosperms (
Besseau et al., 2007;
Hoffmann et al., 2003
). The function of the enzyme in the phenylpropanoid
pathway is to catalyse the transfer of coumarate from p-coumaroyl-CoA to
shikimate, which results in the formation of the corresponding p-coumaroyl
shikimate ester (
Hoffmann et al., 2003
) that is the preferred substrate for the
following C3H enzyme (
Fig. 4
).
