TY - JOUR
T1 - Phenylcoumaran Benzylic Ether Reductase Prevents Accumulation of Compounds Formed under Oxidative Conditions in Poplar Xylem
AU - Niculaes, Claudiu
AU - Morreel, Kris
AU - Kim, Hoon
AU - Lu, Fachuang
AU - McKee, Lauren S.
AU - Ivens, Bart
AU - Haustraete, Jurgen
AU - Vanholme, Bartel
AU - De Rycke, Riet
AU - Hertzberg, Magnus
AU - Fromm, Jorg
AU - Bulone, Vincent
AU - Polle, Andrea
AU - Ralph, John
AU - Boerjana, Wout
N1 - Publisher Copyright:
© 2014 American Society of Plant Biologists. All rights reserved.
PY - 2014/9
Y1 - 2014/9
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84908257980&partnerID=8YFLogxK
U2 - 10.1105/tpc.114.125260
DO - 10.1105/tpc.114.125260
M3 - Article
C2 - 25238751
AN - SCOPUS:84908257980
VL - 26
SP - 3775
EP - 3791
JO - Plant Cell
JF - Plant Cell
SN - 1040-4651
IS - 9
ER -