Chemical regulation of distance.  Characterization of the first natural host germination stimulant for Striga asiatica

Chang, Mu‐Chieh; Netzly, David H.; Butler, Larry G.; Lynn, David G.

doi:10.1021/ja00284a074

Cited by 165 publications

(112 citation statements)

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“…Gas chromatography-mass spectrometry (GC-MS) 1 was performed on a JEOL (JEOL USA, Inc., Peabody, MA) GCMate II system. The GC temperature program was as follows: the initial 120°C was raised to 280°C at a rate of 20°C/min and held at this temperature for 1 min, then raised to 300°C at a rate of 10°C/min and held at this temperature for 4 min.…”

Section: Methodsmentioning

confidence: 99%

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Dayan

Kagan

Rimando

2003

Journal of Biological Chemistry

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NMR analyses of the labeling pattern obtained using various 13 C-labeled precursors indicated that both the lipid tail and the quinone head of sorgoleone, the main allelopathic component of the oily root exudate of Sorghum bicolor, were derived from acetate units, but that the two moieties were synthesized in different subcellular compartments. The 16:3 fatty acid precursor of the tail is synthesized by the combined action of fatty-acid synthase and desaturases most likely in the plastids. It is then exported out of the plastids and converted to 5-pentadecatriene resorcinol by a polyketide synthase. This resorcinol intermediate was identified in root hair extracts. The lipid resorcinol intermediate is then methylated by a S-adenosylmethionine-dependent O-methyltransferase and subsequently dihydroxylated by a P450 monooxygenase to yield the reduced form of sorgoleone.Sorgoleone (2-hydroxy-5-methoxy-3-[(Z,Z)-8Ј,11Ј,14Ј-pentadecatriene]-p-benzoquinone) (1) is the main allelopathic component of the oily root exudate of sorghum (Sorghum bicolor (L.) Moench) ( Fig. 1) (1-3). The term sorgoleone is also used to describe a group of lipophilic p-benzoquinones structurally related to 1 that are also produced by sorghum roots having a hydroxy and a methoxy substitution at positions 2 and 5, respectively, and either a 15-or 17-carbon aliphatic tail with various degrees of unsaturation at position 3 (3).The primary mechanism of phytotoxic action of 1 is associated with inhibition of photosynthesis in higher plant systems by competing for the binding site of plastoquinone on photosystem II (4 -6). This lipophilic p-benzoquinone is also known to hinder electron transfer reactions involved in mitochondrial respiration and to inhibit the enzyme p-hydroxyphenylpyruvate dioxygenase (7,8).The herbicidal and allelopathic properties of 1 make isolation of the genes responsible for its biosynthesis desirable, as manipulation of those genes in sorghum or their introduction in other plant species could provide a better understanding of the role of 1 in plant-plant interaction and natural weed control. To identify the genes and characterize the enzymes they encode, it is necessary to determine the steps involved in the biosynthesis of 1. Little has been reported on this subject.Sorgoleone is found exclusively as a hydrophobic droplet exuding from the tips of root hairs (2), and a recent investigation of sorghum roots suggested that the production of 1 is compartmentalized in the highly physiologically active root hairs (9). The biosynthesis of secondary metabolites occurring in root hairs has not been studied in detail, although other specialized cells at the interface between a plant surface and its environment (i.e. trichomes) are known to produce unique secondary metabolites (10 -12).It has been postulated that the biosynthesis of 1 and related resorcinolic lipids is the result of the convergence of two pathways, namely the fatty acid biosynthetic pathway for the synthesis of the aliphatic tail and the activity of polyketide synthase-...

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Section: Methodsmentioning

confidence: 99%

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Dayan

Kagan

Rimando

2003

Journal of Biological Chemistry

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“…Wheat root exudates that may have allelopathic potential are phenolic compounds (Wu et al 2001). The major group of root exudates from sorghum with allelopathic properties is the benzoquinonones called sorgoleone {2-hydroxy-5-methoxy-e- [(8Z,11Z-8,11,14-pentadecatriene]-p-benzoquinone} (Chang et al 1986;Belz 2007). Production of allelopathic phenolics by wheat seedling roots grown on agar medium have been shown to vary by types and levels, depending upon the cultivar (Wu et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

2008

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Hypotheses in which sorghum seedlings [Sorghum bicolor (L.) Moench] of different genotypes will differentially modify soil microorganisms and will affect subsequent planting of wheat (Triticum aestivum L.) seedlings, were tested. Wheat cultivar Lewjain, and sorghum genotypes Redlan and RTx433, were planted into soils previously planted with wheat or sorghum in growth chamber experiments. Total culturable fungi and oomycetes, and fluorescent Pseudomonas spp. numbers (cfu) were determined. Pseudomonads were screened for hydrogen cyanide (HCN) production, for the presence of the phlD gene for 2,4-diacetylphloroglucinol production (Phl) and for a region of the operon involved in phenazine-1-carboxylic acid (PCA) production. Pasteurized soils were inoculated with rifampicin-marked strains of Pseudomonas fluorescens then planted with Lewjain, Redlan and RTx433 to assess rhizosphere and soil colonization. Effects of plant species, sorghum genotype and previous crop on culturable fungi and oomycetes, and pseudomonad numbers (cfu g −1 soil) were statistically significant. Soils planted with RTx433 or Lewjain had greater numbers of fungal cfu than soils planted with Redlan. When Lewjain seedlings were grown in soil previously planted with RTx433, there were greater numbers of fungal cfu than when Lewjain was planted into Redlan soil. Wheat planted into wheat soil resulted in statistically significantly fewer numbers of pseudomonads than when planted into sorghum soil. Overall, percentages of HCN-producing pseudomonads increased, especially when wheat seedlings were planted in wheat soil. For most treatments, percent of isolates with Phl declined, except when Redlan was planted into Redlan soil, which resulted in increased Phl isolates. When rifampicin-marked P. fluorescens isolates were applied to pasteurized soil, sorghum seedlings sustained rhizosphere and soil populations similar to those on wheat. Sorghum genotypes may differ in associations with soil microorganisms, Plant Soil

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“…The first naturally occurring germination stimulant to be characterized was the sesquiterpenoid, strigol, present in root exudates of the false host, cotton (5,6). More recently the host plant, sorghum, has been shown to exude a dihydroquinone (2-hydroxy-5-methoxy-3-[(8'Z, 11 'Z)-8', 1', 14'-pentadecatriene]-p-hydroquinone which is a very potent stimulant of germination (4,15). A third compound capable ofstimulating Striga gesnerioides (Willd.)…”

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confidence: 99%

Role of Ethylene in the Germination of the Hemiparasite Striga hermonthica

Logan¹,

Stewart²

1991

Plant Physiol.

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Seed germination of the hemiparasitic angiosperm Striga hermonthica (Del.) Benth is elicited by compounds present in the root exudates of the host plant. Although a variety of compounds can substitute for the host-derived signal, the mechanism through which these act is unknown. In the present study, an inhibitor of ethylene biosynthesis, aminoethoxyvinyl glycine, was (2,7,12,13,19). In this study we examine the hypothesis that ethylene is the germination stimulant for Striga seeds and that host derived germination signals trigger germination by eliciting the biosynthesis of ethylene. MATERIALS AND METHODS Plant Materials, Growth Conditions, and ChemicalsSeeds of Striga hermonthica (Del.) Benth were collected from Wad Medani, Sudan, in 1989. Seeds were surfacesterilized by washing in a 5% v/v solution of sodium hypochlorite (10-14% w/v available chlorine). Conditioning of seed took place on two sterile circles of Whatman No. 1 filter paper, saturated with sterile double-distilled deionized water, in 9 cm perspex Petri dishes incubated at 33°C in the dark for 7 d. Unconditioned seeds were treated as above except incubation was for 24 h only. Throughout the conditioning period the filter papers were saturated with sterile double distilled deionised water. For host root exudate collection, seeds of Sorghum bicolor (L.) Moench cv CSH-1 were surface-sterilized as above and germinated on moist sterile Whatman No. 1 filter paper at 33°C, after 48 h the germinated seeds were placed on nylon grids suspended over 500 cm3 plastic beakers containing a 20% Long Ashton solution (11), so that the radicles were immersed in the solution. Plants were grown in a controlled environment (day temperature 35°C, night temperature 20°C, 16-h day length, light intensity at bench level of 103 Wm2). Four days later, three plants were transferred to 50 cm3 of sterile double-distilled deionized water and incubated at 20 to 25°C in the dark for 24 h; this solution was used as germination stimulant. All chemicals were of analytical grade or higher. AVG4 and ACC were purchased from Sigma while NDE was purchased from Aldrich.

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Chemical regulation of distance. Characterization of the first natural host germination stimulant for Striga asiatica

Cited by 165 publications

References 1 publication

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis

Effect of sorghum seedlings, and previous crop, on soil fluorescent Pseudomonas spp.

Role of Ethylene in the Germination of the Hemiparasite Striga hermonthica

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