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. α-Aminooxy-β-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.
Plant peroxidases are important for several processes, such as defense against pathogens, and auxin metabolism. In this study, we report the active production and secretion of plant peroxidase and mutated enzymes in the bacterium Brevibacillus choshinensis for the first time in the world. We introduced mutations into prxA3a, an anionic peroxidase gene of hybrid aspen, Populus × kitakamiensis, to substitute the amino acid residues at the surface of the protein and analyzed their modified substrate specificities. We have also reported heterologous expression of PrxA3a and mutated enzymes in yeast. Enzymes secreted in the culture medium by B. chosinensis were purified by Ni affinity chromatography, anion-exchange chromatography, and size-exclusion chromatography. The ability of the mutated enzymes to polymerize sinapyl alcohol, a monolignol, was higher than that of the wild-type enzyme. In particular, the FYAW-mutated enzyme produced by the bacterium showed higher polymerization activity, similar to that of the FYAW-mutated enzyme produced by yeast.
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