Induced phenylpropanoid metabolism during suberization and lignification: a comparative analysis

Induction of the biosynthesis of phenylpropanoids was monitored at the enzy me level through measurement of the temporal change in the activity of two marker enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase, (PAL, E.C. 4.1.3.5) and 4-coumaryl-CoA ligase (4-CL, E.C. 6.2.1.12) and two marker enzymes for hydroxycinnamyl alcohol biosynthesis, cinnamoyl-CoA:NAD P(+) oxidoreductase (CCR, E.C. 1.2.1.44) and cinnamyl alcohol dehydrogenase (CAD, E.C. 1.1.1.195) in both suberizing potato (Solanum tuberosum) tubers and lignifying lobiolly pine (Pinus taeda) cell cultures. While measurable activities of PAL, 4-CL and CAD increased upon initiation of suberization in potato tubers, that of CCR did not. By contrast, all four enzymes were i nduced upon initiation of lignification in pine cell cultures. The lack of CCR induction in potato by wound treatment is consistent with the channelli ng of hydroxycinnamoyl-CoA derivatives away from monolignol formation and t oward other hydroxycinnamoyl derivatives such as those that accumulate duri ng suberization.