Wounding stress induces phenylalanine ammonia lyases, leading to the accumulation of phenylpropanoids in the model liverwort Marchantia polymorpha

Wounding stress induces the biosynthesis of various specialized metabolites in plants. In this study, wounding induced the biosynthesis of luteolin, apigenin, and isoriccardin C, which are biosynthesized through the phenylpropanoid pathway, in the model liverwort Marchantia polymorpha L (Marchantiaceae). Recombinant M. polymorpha phenylalanine ammonia lyases (MpPALs) exhibited PAL activity in vitro and converted phenylalanine into trans-cinnamic acid. Based on semi-quantitative RT-PCR analysis, the expression levels of the MpPAL genes were up-regulated after wounding. alpha-Aminooxy-beta-phenylpropionic acid, a PAL inhibitor, suppressed the production of wounding-induced phenolic compounds, luteolin, apigenin, and isoriccardin C, in M. polymorpha. Thus, PAL is a committed step in the biosynthesis of phenylpropanoids in response to wounding in M. polymorpha. This study suggests that wound-induced specialized metabolites such as phenylpropanoids comprise a conserved defense system in land plants.