| 1. |
- Andersson, Pierre, et al.
(författare)
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Viridin-like steroids from Hymenoscyphus pseudoalbidus
- 2013
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 86, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- Three furanosteroids were isolated from the ash dieback causing fungus Hymenoscyphus pseudoalbidus along with the known compounds viridiol and demethoxyviridiol. The compounds were characterized by 1D and 2D NMR spectroscopy, LC-HRMS and polarimetry. (C) 2012 Elsevier Ltd. All rights reserved.
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| 2. |
- Barros-Rios, Jaime, et al.
(författare)
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Divergent selection for ester-linked diferulates in maize pith stalk tissues. Effects on cell wall composition and degradability
- 2012
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 83, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- Cross-linking of grass cell wall components through diferulates (DFAs) has a marked impact on cell wall properties. However, results of genetic selection for DFA concentration have not been reported for any grass species. We report here the results of direct selection for ester-linked DFA concentration in maize stalk pith tissues and the associated changes in cell wall composition and biodegradability. After two cycles of divergent selection, maize populations selected for higher total DFA (DFAT) content (CHs) had 16% higher DFAT concentrations than populations selected for lower DFAT content (as). These significant DFA concentration gains suggest that DFA deposition in maize pith parenchyma cell walls is a highly heritable trait that is genetically regulated and can be modified trough conventional breeding. Maize populations selected for higher DFAT had 13% less glucose and 10% lower total cell wall concentration than CLs, suggesting that increased cross-linking of feruloylated arabinoxylans results in repacking of the matrix and possibly in thinner and firmer cell walls. Divergent selection affected esterified DFAT and monomeric ferulate ether cross link concentrations differently, supporting the hypothesis that the biosynthesis of these cell wall components are separately regulated. As expected, a more higher DFA ester cross-coupled arabinoxylan network had an effect on rumen cell wall degradability (CLs showed 12% higher 24-h total polysaccharide degradability than CHs). Interestingly, 8-8-coupled DFAs, previously associated with cell wall strength, were the best predictors of pith cell wall degradability (negative impact). Thus, further research on the involvement of these specific DFA regioisomers in limiting cell wall biodegradability is encouraged. (C) 2012 Elsevier Ltd. All rights reserved.
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| 3. |
- Burman, Robert, et al.
(författare)
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Cyclotide proteins and precursors from the genus Gloeospermum : filling a blank spot in the cyclotide map of Violaceae
- 2010
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 71:1, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- Cyclotides are disulfide-rich plant proteins that are exceptional in their cyclic structure; their N and C termini are joined by a peptide bond, forming a continuous circular backbone, which is reinforced by three interlocked disulfide bonds. Cyclotides have been found mainly in the coffee (Rubiaceae) and violet (Violaceae) plant families. Within the Violaceae, cyclotides seem to be widely distributed, but the cyclotide complements of the vast majority of Violaceae species have not yet been explored. This study provides insight into cyclotide occurrence, diversity and biosynthesis in the Violaceae, by identifying mature cyclotide proteins, their precursors and enzymes putatively involved in their biosynthesis in the tribe Rinoreeae and the genus Gloeospermum. Twelve cyclotides from two Panamanian species, Gloeospermum pauciflorum Hekking and Gloeospermum blakeanum (Standl.) Hekking (designated Glopa A-E and Globa A-G, respectively) were characterised through cDNA screening and protein isolation. Screening of cDNA for the oxidative folding enzymes protein-disulfide isomerase (PDI) and thioredoxin (TRX) resulted in positive hits in both species. These enzymes have demonstrated roles in oxidative folding of cyclotides in Rubiaceae, and results presented here indicate that Violaceae plants have evolved similar mechanisms of cyclotide biosynthesis. We also describe PDI and TRX sequences from a third cyclotide-expressing Violaceae species, Viola biflora L., which further support this hypothesis.
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| 4. |
- Cleary, Michelle, et al.
(författare)
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Genotypes of Fraxinus excelsior with different susceptibility to the ash dieback pathogen Hymenoscyphus pseudoalbidus and their response to the phytotoxin viridiol - A metabolomic and microscopic study
- 2014
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 102, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- Eight European ash (Fraxinus excelsior) genotypes with different known susceptibility to Hymenoscyphus pseudoalbidus were tested against the phytotoxin viridiol and their response described at the microscopic and metabolomic level. All ash genotypes were sensitive to the toxin and necrosis was detectable after 24 h. Among the three viridiol concentrations used in the experiment, the lowest concentration (14.7 mu M) yielded markedly lower mean damage scores compared to those resulting from seedlings tested at higher dosages. The highest damage scores were associated with the susceptible ash clones S-101, S-106 and S-125, but also with resistant clone R-104. Three resistant clones (R-131, R-121, and R-118) had lower mean damage scores compared to susceptible clones. Wilting of leaves was more common 48 h after treatment and more pronounced on seedlings with high damage scores. The resulting lesions generally lacked browning of tissue and displayed only surface disruption of cells in direct contact with the toxin. A delay in symptom development was evident on all five resistant clones tested with the two higher concentrations of viridiol. LC-HRMS and MS/MS analyses of ash seedling extracts suggest several secoiridoid compounds as well as compounds related to abscisic acid (ABA) to be produced in response to viridiol. ABA-cysteine and xanthoxin were found at significantly higher concentrations in susceptible clones compared to resistant clones after treatment with viridiol, suggesting a primary role of ABA in response to stress. The results observed in this study suggest that genetic resistance to H. pseudoalbidus among ash genotypes may be explained, in part, by the varied response to phytotoxins produced by the fungus. (C) 2014 Elsevier Ltd. All rights reserved.
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| 5. |
- Correa, Edwin, et al.
(författare)
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Prenylhydroxybenzoic acid compounds with pungent activity from Piper arieianum (CDC) leaves
- 2011
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422. ; 72:2-3, s. 238-241
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Tidskriftsartikel (refereegranskat)abstract
- Prenylhydroxybenzoic acid derivatives and other two analogues previously reported were isolated from Piper arieianum leaves. The structures of the compounds were assigned from detailed spectroscopical analysis (NMR 1D and 2D and HR ESI TOF MS) data and by comparison with data from the literature. These molecules posses pungent activity different to that of capsaicin and their activity is related to their structure and their mechanism of action can involve interactions with TRPV1 channel. (C) 2010 Elsevier Ltd. All rights reserved.
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| 6. |
- Decker, Daniel, et al.
(författare)
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Substrate kinetics and substrate effects on the quaternary structure of barley UDP-glucose pyrophosphorylase
- 2012
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 79, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- UDP-Glc pyrophosphorylase (UGPase) is an essential enzyme responsible for production of UDP-Glc, which is used in hundreds of glycosylation reactions involving addition of Glc to a variety of compounds. In this study, barley UGPase was characterized with respect to effects of its substrates on activity and quaternary structure of the protein. Its K(m) values with Glc-1-P and UTP were 0.33 and 0.25 mM, respectively. Besides using Glc-1-P as a substrate, the enzyme had also considerable activity with Gal-1-P; however, the K(m) for Gal-1-P was very high (>10 mM), rendering this reaction unlikely under physiological conditions. UGPase had a relatively broad pH optimum of 6.5-8.5, regardless of the direction of reaction. The enzyme equilibrium constant was 0.4, suggesting slight preference for the Glc-1-P synthesis direction of the reaction. The quaternary structure of the enzyme, studied by Gas-phase Electrophoretic Mobility Macromolecule Analysis (GEMMA), was affected by addition of either single or both substrates in either direction of the reaction, resulting in a shift from UGPase dimers toward monomers, the active form of the enzyme. The substrate-induced changes in quaternary structure of the enzyme may have a regulatory role to assure maximal activity. Kinetics and factors affecting the oligomerization status of UGPase are discussed.
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| 7. |
- Gandla, Madhavi Latha, et al.
(författare)
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Expression of a fungal glucuronoyl esterase in Populus : Effects on wood properties and saccharification efficiency
- 2015
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 112, s. 210-220
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Tidskriftsartikel (refereegranskat)abstract
- The secondary walls of angiosperms contain large amounts of glucuronoxylan that is thought to be covalently linked to lignin via ester bonds between 4-O-methyl-alpha-D-glucuronic acid (4-O-Me-GlcA) moieties in glucuronoxylan and alcohol groups in lignin. This linkage is proposed to be hydrolysed by glucuronoyl esterases (GCEs) secreted by wood-degrading fungi. We report effects of overexpression of a GCE from the white-rot basidiomycete Phanerochaete carnosa, PcGCE, in hybrid aspen (Populus tremula L. x tremuloides Michx.) on the wood composition and the saccharification efficiency. The recombinant enzyme, which was targeted to the plant cell wall using the signal peptide from hybrid aspen cellulase PttCel9B3, was constitutively expressed resulting in the appearance of GCE activity in protein extracts from developing wood. Diffuse reflectance FT-IR spectroscopy and pyrolysis-GC/MS analyses showed significant alternation in wood chemistry of transgenic plants including an increase in lignin content and S/G ratio, and a decrease in carbohydrate content Sequential wood extractions confirmed a massive (+43%) increase of Klason lignin, which was accompanied by a ca. 5% decrease in cellulose, and ca. 20% decrease in wood extractives. Analysis of the monosaccharide composition using methanolysis showed a reduction of 4-O-Me-GlcA content without a change in Xyl contents in transgenic lines, suggesting that the covalent links between 4-O-Me-GlcA moieties and lignin protect these moieties from degradation. Enzymatic saccharification without pretreatment resulted in significant decreases of the yields of Gal, Glc, Xyl and Man in transgenic lines, consistent with their increased recalcitrance caused by the increased lignin content In contrast, the enzymatic saccharification after acid pretreatment resulted in Glc yields similar to wild-type despite of their lower cellulose content. These data indicate that whereas PcGCE expression in hybrid aspen increases lignin deposition, the inhibitory effects of lignin are efficiently removed during acid pretreatment, and the extent of wood cellulose conversion during hydrolysis after acid pretreatment is improved in the transgenic lines possible due to reduced cell wall cross-links between cell wall biopolymers by PcGCE.
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| 8. |
- Glinwood, Robert, et al.
(författare)
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Chemical interaction between undamaged plants - Effects on herbivores and natural enemies
- 2011
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 72, s. 1683-1689
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Forskningsöversikt (refereegranskat)abstract
- Most research on plant-plant chemical interactions has focussed on events following herbivore or pathogen attack. However, undamaged plants also interact chemically as a natural facet of their behaviour, and this may have consequences for insects that use the plants as hosts. In this review, the links between allelopathy and insect behaviour are outlined. Findings on how chemical interactions between different plant species and genotypes affect aphid herbivores and their natural enemies are reviewed, and the role of plant diversity and chemical interaction for trophic interactions in crops is discussed. (C) 2011 Elsevier Ltd. All rights reserved.
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| 9. |
- Hamada, Afaf M., et al.
(författare)
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Thiamine treatments alleviate aphid infestations in barley and pea
- 2013
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 94, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of plants with thiamine (Vitamin B1) has before been shown to activate plant defence against microorganisms. Here, we have studied the effects of thiamine treatments of plants on aphid reproduction and behaviour. The work was mainly carried out with bird cherry-oat aphid (Rhopalosiphum padi L.) on barley (Hordeum vulgare L.). Aphid population growth and aphid acceptance on plants grown from seeds soaked in a 150 mu M thiamine solution were reduced to ca. 60% of that on control plants. R. padi life span and the total number of offspring were reduced on barley plants treated with thiamine. Healthy aphids and aphids infected with the R. padi virus were similarly affected. Spraying or addition of thiamine at 150 mu M to nutrient solutions likewise resulted in reduced aphid population growth to ca. 60%, as did plant exposure to thiamine odour at 4 mM. Thiamine treatments resulted in reduced aphid population growth also when tested with grain aphid (Sitobion avenae F.) on barley and pea aphid (Acyrthosiphon pisum H.) on pea (Pisum sativum L). There was no direct effect of thiamine on aphid reproduction or thiamine odour on aphid behaviour, as evaluated using artificial diets and by olfactometer tests, respectively. Two gene sequences regulated by salicylic acid showed higher transcript abundance and one gene sequence regulated by methyl jasmonate showed lower transcript abundance in thiamine-treated plants but not in control plants after aphid infestation. These results suggest that the aphid antibiosis and antixenosis effects may be related to priming of defence, but more studies are needed to explain the effects against aphids.
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| 10. |
- Han, Junli, et al.
(författare)
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Effects of overexpression of AaWRKY1 on artemisinin biosynthesis in transgenic Artemisia annua plants
- 2014
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 102, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- The effective anti-malarial medicine artemisinin is costly because of the low content in Artemisia annua. Genetic engineering of A. annua is one of the most promising approaches to improve the yield of artemisinin. In this work, the transcription factor AaWRKY1, which is thought to be involved in the regulation of artemisinin biosynthesis, was cloned from A. annua var. Chongqing and overexpressed using the CaMV35S promoter or the trichome-specific CYP71AV1 promoter in stably transformed A. annua plants. The transcript level of AaWRKY1 was increased more than one hundred times under the CaMV35S promoter and about 40 times under the CYP71AV1 promoter. The overexpressed AaWRKY1 activated the transcription of CYP71AV1 and moreover the trichome-specific overexpression of AaWRKY1 improved the transcription of CYP71AV1 much more effectively than the constitutive overexpression of AaWRKY1, i.e. up to 33 times as compared to the wild-type plant. However the transcription levels of FDS, ADS, and DBR2 did not change significantly in transgenic plants. The significantly up-regulated CYP71AV1 promoted artemisinin biosynthesis, i.e. up to about 1.8 times as compared to the wild-type plant. It is demonstrated that trichome-specific overexpression of AaWRKY1 can significantly activate the transcription of CYP71AV1 and the up-regulated CYP71AV1 promotes artemisinin biosynthesis.
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