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|Title:||Phenylcoumaran benzylic ether reductase prevents accumulation of compounds formed under oxidative conditions in poplar xylem|
De Rycke, R.
|Citation:||The Plant Cell, 2014; 26(9):3775-3791|
|Publisher:||American Society of Plant Biologists|
|C. Niculaes, K. Morreel, H. Kim, F. Lu, L.S. McKee, B. Ivens, J. Haustraete, B. Vanholme, R. De Rycke, M. Hertzberg, J. Fromm, V. Bulone, A. Polle, J. Ralph and W. Boerjana|
|Abstract:||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.|
|Keywords:||Cell Wall; Plants, Genetically Modified; Populus; Lignans; Cysteine; Oxidoreductases; Amino Acids; Immunoblotting; Magnetic Resonance Spectroscopy; Reproducibility of Results; Down-Regulation; Substrate Specificity; Oxidation-Reduction; Oxidative Stress; Phenotype; Molecular Sequence Data; Mass Spectrometry; Xylem; Enzyme Assays|
|Rights:||© 2014 American Society of Plant Biologists. All rights reserved.|
|Appears in Collections:||Agriculture, Food and Wine publications|
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