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Structure and Biosynthesis of Lignin
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
These reactions are mediated by A phenylalanine ammonia-lyase (PAL)Three different cytochrome P450-dependent monooxygenases: cinnamate 4-hydroxylase (C4H), p-coumarate 3-hydroxylase (C3H), and ferulate 5-hydroxylase (F5H)Two methyltransferases: caffeoyl-CoA O-methyltransferase (CCoAOMT; CoA, coenzyme A) and caffeic acid O-methyltransferase (COMT)Two oxidoreductases: cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD)1
Right on target: using plants and microbes to remediate explosives
Published in International Journal of Phytoremediation, 2019
Elizabeth L. Rylott, Neil C. Bruce
The fate of UGT and GST-catalyzed TNT conjugates is still to be determined. In Arabidopsis, glutathionylated xenobiotics can be compartmentalized to the vacuole by MRP2, an ATP-binding cassette transporter belonging to the multidrug resistance-associated protein (MRP) family. MRP2 is upregulated in TNT-fed Arabidopsis (Gandia-Herrero et al. 2008), but compartmentation and the ultimate fate of TNT conjugates are still to be elucidated. Towards this, subcellular fractionation studies on bean (Phaseolus vulgaris) fed 14C TNT found over half of the label in the lignin fraction (Sens et al. 1998, 1999). Tobacco (Nicotiana tabacum) cell suspension cultures fed TNT, accumulate more mono and diglycoside conjugates of 2‐ and 4‐HADNT than are found in whole‐plant cultures (Vila et al. 2005), possibly because of the lack of a significant lignin sink for incorporation of these conjugates. In agreement with this finding, a gene expression study in Arabidopsis roots treated with TNT identified upregulation of lignin biosynthesis genes (including phenyl ammonium lyase, cinnamate 4‐hydroxylase, 4‐coumarate CoA ligase, hydroxycinnamoyltransferase, cinnamoyl‐CoA reductase, caffeic acid O‐methyltransferase and cinnamyl alcohol dehydrogenase; Ekman et al. 2003). Thus is it plausible that TNT conjugates are incorporated, through non-enzymatic free radical polymerization and self-assembly, into root cell wall lignin? Subsequent metabolism is likely to occur during natural composting of dead plant material, with mineralization of any re-released TNT-intermediates by fungal lignolytic activities, as described above (Rylott and Bruce 2009; Rylott, Lorenz, et al. 2011).