Phenolic extractives of the leaves of Populus balsamifera and of P. trichocarpa

Pearl, Irwin A.; Darling, Stephen F.

doi:10.1016/s0031-9422(00)97307-2

Cited by 23 publications

(9 citation statements)

References 8 publications

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“…The expression of poplar genes encoding specific PAL and 4CL isoforms in the epidermal or subepidermal cells of young leaf has been shown by in situ hybridization or promoter-GUS analysis (Subramaniam et al, 1993;Hu et al, 1998;Gray-Mitsumune et al, 1999). Poplar buds and young leaves are rich in phenolic compounds, including flavonoids and hydroxycinnamic acid conjugates and esters (Pearl and Darling, 1971;English et al, 1991), whose biosynthesis requires P450 enzymes, suggesting that the epidermal and subepidermal cells of these organs may require high levels of CPR activity. In situ hybridization and promoter-GUS fusions could determine the precise cell type-specific expression of CPR2 relative to CPR1 and CPR3 in poplar leaves.…”

Section: Cpr Expression Patterns In Poplarmentioning

confidence: 99%

Cloning, Functional Expression, and Subcellular Localization of Multiple NADPH-Cytochrome P450 Reductases from Hybrid Poplar

2002

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NADPH:cytochrome P450 reductase (CPR) provides reducing equivalents to diverse cytochrome P450 monooxygenases. We isolated cDNAs for three CPR genes (CPR1, CPR2, and CPR3) from hybrid poplar (Populus trichocarpa ϫ Populus deltoides). Deduced CPR2 and CPR3 amino acid sequences were 91% identical, but encoded isoforms divergent from CPR1 (72% identity). CPR1 and CPR2 were co-expressed together with the P450 enzyme cinnamate-4-hydroxylase (C4H) in yeast (Saccharomyces cerevisiae). Microsomes isolated from strains expressing CPR1/C4H or CPR2/C4H enhanced C4H activities approximately 10-fold relative to the C4H-only control strain, and catalyzed NADPH-dependent cytochrome c reduction. The divergent CPR isoforms (CPR1 and CPR2/3) contained entirely different N-terminal sequences, which are conserved in other plant CPRs and are diagnostic for two distinct classes of CPRs within the angiosperms. C-terminal green fluorescent protein fusions to CPR1 and CPR2 were constructed and expressed in both yeast and Arabidopsis. The fusion proteins expressed in yeast retained the ability to support C4H activity and, thus, were catalytically active. Both CPR::green fluorescent protein fusion proteins were strictly localized to the endoplasmic reticulum in transgenic Arabidopsis. The lack of localization of either isoform to chloroplasts, where P450s are known to be present, suggests that an alternative P450 reduction system may be operative in this organelle. Transcripts for the three poplar CPR genes were present ubiquitously in all tissues examined, but CPR2 showed highest expression in young leaf tissue.Cytochrome P450 monooxygenase enzymes (P450s) play key roles in a wide range of oxidative metabolic reactions in various organisms from microbes to humans. In animals, xenobiotic detoxification and sterol biosynthesis are the major functions of P450s. However, P450-mediated reactions in plants encompass a much broader spectrum, including biosynthesis of plant hormones and signal molecules, defenserelated chemicals and structural secondary natural products, and herbicide detoxification (for review, see Werck-Reichhart et al., 2000;Feldmann, 2001). The Arabidopsis genome encodes 273 P450 genes (www.biobase.dk/P450), highlighting the important biochemical roles of P450-mediated reactions that have evolved in plants.Most eukaryotic P450s are not self-sufficient enzymes, and their catalytic activities strictly rely on an electron donor, NADPH:cytochrome P450 reductase (CPR; Lu et al., 1969). CPR (EC 1.6.2.4) transfers two electrons from NADPH to diverse P450s via two prosthetic groups, FAD and FMN, in sequence as electron entry and exit ports, respectively (Iyanagi and Mason, 1973;Vermilion et al., 1981). Both P450s and CPR are integral membrane-bound proteins, and the reducing equivalents are delivered mainly through transient electrostatic interactions on the endoplasmic reticulum (ER) membrane (Nisimoto, 1986;Shen and Kasper, 1995). CPR is also known to transfer electrons to cytochrome b 5 , which forms part of electron transport ch...

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Section: Cpr Expression Patterns In Poplarmentioning

confidence: 99%

Cloning, Functional Expression, and Subcellular Localization of Multiple NADPH-Cytochrome P450 Reductases from Hybrid Poplar

2002

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“…Poplars synthesize and accumulate several classes of phenolic metabolites, including salicinoids (phenolic glycosides), anthocyanins, PAs, and low molecular weight phenolic acids and their esters, in leaves, stems, and roots (Pearl and Darling, 1971;Palo, 1984;Tsai et al, 2006;Boeckler et al, 2011). Salicinoids and PAs are generally the most abundant secondary metabolites and together can make up to 30% to 35% of leaf dry weight (Lindroth and Hwang, 1996;Tsai et al, 2006).…”

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confidence: 99%

Flavan-3-ols Are an Effective Chemical Defense against Rust Infection

et al. 2017

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Phenolic secondary metabolites are often thought to protect plants against attack by microbes, but their role in defense against pathogen infection in woody plants has not been investigated comprehensively. We studied the biosynthesis, occurrence, and antifungal activity of flavan-3-ols in black poplar (Populus nigra), which include both monomers, such as catechin, and oligomers, known as proanthocyanidins (PAs). We identified and biochemically characterized three leucoanthocyanidin reductases and two anthocyanidin reductases from P. nigra involved in catalyzing the last steps of flavan-3-ol biosynthesis, leading to the formation of catechin [2,3-trans-(+)-flavan-3-ol] and epicatechin [2,3-cis-(2)-flavan-3-ol], respectively. Poplar trees that were inoculated with the biotrophic rust fungus (Melampsora larici-populina) accumulated higher amounts of catechin and PAs than uninfected trees. The de novo-synthesized catechin and PAs in the rust-infected poplar leaves accumulated significantly at the site of fungal infection in the lower epidermis. In planta concentrations of these compounds strongly inhibited rust spore germination and reduced hyphal growth. Poplar genotypes with constitutively higher levels of catechin and PAs as well as hybrid aspen (Populus tremula 3 Populus alba) overexpressing the MYB134 transcription factor were more resistant to rust infection. Silencing PnMYB134, on the other hand, decreased flavan-3-ol biosynthesis and increased susceptibility to rust infection. Taken together, our data indicate that catechin and PAs are effective antifungal defenses in poplar against foliar rust infection.

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“…The phenolic metabolites produced by poplar are thought to be important determinants of community structure and ecosystem dynamics (Lindroth and Hwang, 1996;Schweitzer et al, 2004;Bailey et al, 2005;LeRoy et al, 2006;Whitham et al, 2006). Poplar leaves typically accumulate several classes of phenolic metabolites, including the salicylate-derived phenolic glycosides (PGs), flavonoids such as flavonol glycosides, anthocyanins, and proanthocyanidins (PAs; or condensed tannins), and numerous small phenolic acids and their esters (Pearl and Darling, 1971;Klimczak et al, 1972;Palo, 1984;Lindroth and Hwang, 1996;Fig. 1).…”

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confidence: 99%

The Wound-, Pathogen-, and Ultraviolet B-ResponsiveMYB134Gene Encodes an R2R3 MYB Transcription Factor That Regulates Proanthocyanidin Synthesis in Poplar

Mellway

Tran²,

Prouse³

et al. 2009

Plant Physiology

254

231

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In poplar (Populus spp.), the major defense phenolics produced in leaves are the flavonoid-derived proanthocyanidins (PAs) and the salicin-based phenolic glycosides. Transcriptional activation of PA biosynthetic genes leading to PA accumulation in leaves occurs following herbivore damage and mechanical wounding as well as infection by the fungal biotroph Melampsora medusae. In this study, we have identified a poplar R2R3 MYB transcription factor gene, MYB134, that exhibits close sequence similarity to the Arabidopsis (Arabidopsis thaliana) PA regulator TRANSPARENT TESTA2 and that is coinduced with PA biosynthetic genes following mechanical wounding, M. medusae infection, and exposure to elevated ultraviolet B light. Overexpression of MYB134 in poplar resulted in transcriptional activation of the full PA biosynthetic pathway and a significant plant-wide increase in PA levels, and electrophoretic mobility shift assays showed that recombinant MYB134 protein is able to bind to promoter regions of PA pathway genes. MYB134-overexpressing plants exhibited a concomitant reduction in phenolic glycoside concentrations and other minor alterations to levels of small phenylpropanoid metabolites. Our data provide insight into the regulatory mechanisms controlling stress-induced PA metabolism in poplar, and the identification of a regulator of stress-responsive PA biosynthesis constitutes a valuable tool for manipulating PA metabolism in poplar and investigating the biological functions of PAs in resistance to biotic and abiotic stresses.

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Phenolic extractives of the leaves of Populus balsamifera and of P. trichocarpa

Cited by 23 publications

References 8 publications

Cloning, Functional Expression, and Subcellular Localization of Multiple NADPH-Cytochrome P450 Reductases from Hybrid Poplar

Cloning, Functional Expression, and Subcellular Localization of Multiple NADPH-Cytochrome P450 Reductases from Hybrid Poplar

Flavan-3-ols Are an Effective Chemical Defense against Rust Infection

The Wound-, Pathogen-, and Ultraviolet B-ResponsiveMYB134Gene Encodes an R2R3 MYB Transcription Factor That Regulates Proanthocyanidin Synthesis in Poplar

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