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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
In addition to these eight enzymes, of which actions are apparent in the final pathways products, two more enzymes, 4-coumarate:CoA ligase (4CL) and p-hydroxycinnamoyl-CoA:quinate/shikimate p-hydroxycinnamoyltransferase (HCT), are required to synthesize pathway intermediates that serve as substrates for subsequent reactions.1 4CL is an ATP-dependent CoA ligase that catalyzes the synthesis of p-coumaroyl CoA. This p-coumaroyl CoA is then used as an acyl donor by acyltransferase HCT to synthesize p-coumaroyl shikimate, the substrate for 3-hydroxylation by C3H. Alternatively, p-coumaroyl CoA can serve as a substrate for chalcone synthase, diverting it to the flavonoid pathway, or CCR, committing it to H lignin biosynthesis.
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).
Impact of copper treatment on phenylpropanoid biosynthesis in adventitious root culture of Althaea officinalis L.
Published in Preparative Biochemistry & Biotechnology, 2022
Yun Ji Park, Nam Su Kim, Ramaraj Sathasivam, Yong Suk Chung, Sang Un Park
The real-time PCR reactions contained, at a total volume of 20 μL, 5 μL of diluted cDNA (1:20), 1 μL of each forward and reverse primer (10 pmol/μL), 10 μL of 2X Real-Time PCR Master Mix (Including SFC green® I) (BIOFACT, Korea), and 3 μL of distilled water. Gene expression profiling was performed using a CFX96 real-time system (BIO-RAD Laboratories, USA), under the following thermal cycling conditions: 15 min at 95 °C, 40 cycles of denaturation at 95 °C for 20 s, alignment step at 56 °C for 40 s, and elongation step at 72 °C for 20 s. Glyceraldehyde 3-phosphate dehydrogenase gene from A. officinalis (AoGAPDH) was used as a housekeeping gene to determine relative transcript abundance. Moreover, seventeen phenylpropanoid biosynthetic genes, including phenylalanine ammonia-lyase (AoPALs), cinnamate 4-hydroxylase (AoC4H), 4-coumarate-CoA ligase, (Ao4CL), chalcone synthase (AoCHSs), chalcone isomerase (AoCHIs), flavanone 3-hydroxylase (AoF3H), flavonol synthase (AoFLS), anthocyanidin reductase (AoANR), dihydroflavonol 4-reductase (AoDFR), anthocyanidin synthase (AoANS), 4-coumarate 3-hydroxylase (AoC3Hs), Hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (AoHCT), and Hydroxycinnamoyl CoA quinate transferase (AoHQT) were determined from A. officinalis[21]. The primers used in this study were designed using the GenScript Real-time PCR (TaqMan) Primer Design (www.genscript.com) and are listed in Table 1. For each condition, qRT-PCR experiments were conducted in triplicate. The specificity of the PCR reaction was confirmed by melting curve analysis of each amplified product. Standard curves were drawn to confirm the efficiency (E) for the qPCR assay and the coefficient (R2) of the serial dilutions. The relative gene expression levels were measured using the 2 –ΔΔCt method.[22]