Phenylcoumaran Benzylic Ether Reductase Prevents Accumulation of Compounds Formed under Oxidative Conditions in Poplar Xylem

Claudiu Niculaes, Kris Morreel, Hoon Kim, Fachuang Lu, Lauren S. McKee, Bart Ivens, Jurgen Haustraete, Bartel Vanholme, Riet De Rycke, Magnus Hertzberg, Jorg Fromm, Vincent Bulone, Andrea Polle, John Ralph, Wout Boerjana

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


Phenylcoumaran benzylic ether reductase (PCBER) is one of the most abundant proteins in poplar (Populus spp) xylem, but its biological role has remained obscure. In this work, metabolite profiling of transgenic poplar trees downregulated in PCBER revealed both the in vivo substrate and product of PCBER. Based on mass spectrometry and NMR data, the substrate was identified as a hexosylated 8–5-coupling product between sinapyl alcohol and guaiacylglycerol, and the product was identified as its benzyl-reduced form. This activity was confirmed in vitro using a purified recombinant PCBER expressed in Escherichia coli. Assays performed on 20 synthetic substrate analogs revealed the enzyme specificity. In addition, the xylem of PCBER-downregulated trees accumulated over 2000-fold higher levels of cysteine adducts of monolignol dimers. These compounds could be generated in vitro by simple oxidative coupling assays involving monolignols and cysteine. Altogether, our data suggest that the function of PCBER is to reduce phenylpropanoid dimers in planta to form antioxidants that protect the plant against oxidative damage. In addition to describing the catalytic activity of one of the most abundant enzymes in wood, we provide experimental evidence for the antioxidant role of a phenylpropanoid coupling product in planta.

Original languageEnglish
Pages (from-to)3775-3791
Number of pages17
JournalPlant Cell
Issue number9
Publication statusPublished - Sep 2014
Externally publishedYes

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© 2014 American Society of Plant Biologists. All rights reserved.


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