Search

Orobanchaceae root parasitic weeds cause significant damage to agriculture and become threats to global food security. Integrated pest management is a key concept in modern agriculture and requires chemicals with various modes of action. Planteose accumulates as a storage carbohydrate in the dry seeds of root parasitic weeds. In Orobanche minor seeds, planteose is hydrolyzed by an a-galactosidase, OmAGAL2, during germination. It was found that the OmAGAL2 inhibitor, PI-28, suppressed the radicle elongation of germinating O. minor seeds. This inhibitory activity against O. minor radicle elongation was evaluated for a series of aryloxyacetylthioureas synthesized based on the structure of PI-28. Compounds with a 3-Cl or 4-Cl substituent on the benzene ring in the phenoxy moiety in PI-28 exhibited more potent activity than the parent PI-28. This is the first report on the effect of aryloxyacetylthioureas on a root parasitic weed and will contribute to the development of control reagents for root parasitic weeds. [ABSTRACT FROM AUTHOR]

Root parasitic weeds of the Orobanchaceae, such as witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.), cause serious losses in agriculture worldwide, and efforts have been made to control these parasitic weeds. Understanding the characteristic physiological processes in the life cycle of root parasitic weeds is particularly important to identify specific targets for growth modulators. In our previous study, planteose metabolism was revealed to be activated soon after the perception of strigolactones in germinating seeds of O. minor. Nojirimycin inhibited planteose metabolism and impeded seed germination of O. minor , indicating a possible target for root parasitic weed control. In the present study, we investigated the distribution of planteose in dry seeds of O. minor by matrix-assisted laser desorption/ionization–mass spectrometry imaging. Planteose was detected in tissues surrounding—but not within—the embryo, supporting its suggested role as a storage carbohydrate. Biochemical assays and molecular characterization of an α-galactosidase family member, OmAGAL2, indicated that the enzyme is involved in planteose hydrolysis in the apoplast around the embryo after the perception of strigolactones, to provide the embryo with essential hexoses for germination. These results indicate that OmAGAL2 is a potential molecular target for root parasitic weed control. [ABSTRACT FROM AUTHOR]

Damage caused by Orobanchaceae root parasitic weeds is a substantial agricultural problem for global food security. Many studies have been conducted to establish practical methods of control, but efforts are still required for successful management. Seed germination of root parasitic weeds requires host-derived germination stimulants including strigolactones (SLs). Studies on SLs have revealed that a butenolide ring is the essential moiety for SL activity as a germination stimulant. Interestingly, recent studies have revealed that butenolide hormones regulate the biosynthesis of secondary metabolites and mediate communication in actinomycete bacteria. Because of the structural similarity between SLs and the bacterial butenolides, we evaluated the germination stimulatory activity of butenolides isolated from Streptomyces albus J1074 on root parasitic weeds. These butenolides were found to specifically induce seed germination of Orobanche minor. Our findings contribute to understanding the molecular mechanisms of germination stimulant perception and to the development of a method for their biological control. [ABSTRACT FROM AUTHOR]

Orobanchaceae root parasitic weeds cause serious agricultural damage worldwide. Although numerous studies have been conducted to establish an effective control strategy for the growth and spread of root parasitic weeds, no practical method has been developed so far. Previously, metabolomic analyses were conducted on germinating seeds of a broomrape, Orobanche minor, to find novel targets for its selective control. Interestingly, planteose metabolism was identified as a possible target, and nojirimycin (NJ) selectively inhibited the germination of O. minor by intercepting planteose metabolism, although its precise mode of action was unclear. Here, transcriptome analysis by RNA-Seq was conducted to obtain molecular insight into the effects of NJ on germinating O. minor seeds. Differential gene expression analysis results suggest that NJ alters sugar metabolism and/or signaling, which is required to promote seed germination. This finding will contribute to understanding the effect of NJ and establishing a novel strategy for parasitic weed control. [ABSTRACT FROM AUTHOR]

Abstract Root exudates from Lotus japonicus were found to contain at least three different hyphal branching-inducing compounds for the arbuscular mycorrhizal (AM) fungus Gigaspora margarita , one of which had been previously identified as (+)-5-deoxystrigol (5DS), a canonical strigolactone (SL). One of the two remaining unknown hyphal branching inducers was purified and named lotuslactone. Its structure was determined as methyl (E)-2-(3-acetoxy-2-hydroxy-7-methyl-1-oxo-1,2,3,4,5,6-hexahydroazulen-2-yl)-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yl)oxy)acrylate, by 1D and 2D NMR spectroscopy, and HR-ESI- and EI-MS. Although lotuslactone, a non-canonical SL, contains the AB-ring and the enol ether-bridged D-ring, it lacks the C-ring and has a seven-membered cycloheptadiene in the A-ring part as in medicaol, a major SL of Medicago truncatula. Lotuslactone was much less active than 5DS, but showed comparable activity to methyl carlactonoate (MeCLA) in inducing hyphal branching of G. margarita. Other natural non-canonical SLs including avenaol, heliolactone, and zealactone (methyl zealactonoate) were also found to be moderate to weak inducers of hyphal branching in the AM fungus. Lotuslactone strongly elicited seed germination in Phelipanche ramosa and Orobanche minor , but Striga hermonthica seeds were 100-fold less sensitive to this stimulant. Graphical abstract The model legume Lotus japonicus was shown to produce both a canonical and a non-canonical strigolactones as rhizosphere signals. Image 1 Highlights • A novel strigolactone, named lotuslactone, was isolated from Lotus japonicus. • Lotuslactone is a non-canonical strigolactone. • Lotuslactone is a moderate inducer of hyphal branching in Gigaspora margarita. • Lotuslactone is a strong inducer of seed germination in root parasitic plants. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus) plants were found to exude at least 12 germination stimulants for root parasitic weeds including 5 known strigolactones, 7-oxoorobanchol, 7-oxoorobanchyl acetate, orobanchol, orobanchyl acetate, and 4-deoxyorobanchol. Two novel germination stimulants were purified from cucumber root exudates and their structures were determined to be 7α-and 7β-hydroxyorobanchyl acetate by 1D and 2D NMR spectroscopy, and ESI- and EI-MS spectrometry. The stereochemistry was determined by NOE measurement and by comparing the CD spectra with those of the synthetic standards of four stereoisomers of orobanchol. 7α- and 7β-Hydroxyorobanchol were detected by LC-MS/MS, and GC-MS analysis of purified sample confirmed their structures. The germination stimulation activities of 7α- and 7β-hydroxyorobanchyl acetate on Orobanche minor were comparable to those of orobanchyl acetate and 7-oxoorobanchyl acetate. By contrast, 7β-hydroxyorobanchyl acetate was a highly potent germination stimulant for Phelipanche ramosa inducing more than 50% germination at 10 pM. [ABSTRACT FROM AUTHOR]

Highlights: [•] Allelopathic grass Avena strigosa produces no known strigolactones. [•] Avenaol is a C20 germination stimulant structurally related to strigolactones. [•] Avenaol is more active on Phelipanche ramosa, but less active on Striga hermonthica and Orobanche minor. [Copyright &y& Elsevier]

Abstract: (+)-Strigone was described earlier in a paper on isolation of strigol and then recently examined for hyphal branching activity in arbuscular mycorrhizal fungi as a strigolactone. Herein, it was isolated from root exudates of Houttuynia cordata, and its structure was confirmed by direct comparison with synthetic standards in LC–MS/MS, GC–MS, and 1H and 13C NMR analyses. The stereochemistry of strigone was determined by comparing the CD spectra and RR t in chiral LC–MS/MS with those of synthetic (+)-strigone and (−)-strigone. Four stereoisomers of strigone exhibited clearly different levels of stimulation activity on the seeds of three root parasitic plants, Orobanche minor, Phelipanche ramosa, and Striga hermonthica. (+)-Strigone was a highly potent germination stimulant on S. hermonthica and also on P. ramosa, but less active than ent-2′-epi-strigone on O. minor. In addition to strigone, H. cordata was found to produce strigol, sorgomol, and 5-deoxystrigol, indicating that this plant produces mainly strigol-type strigolactones derived from 5-deoxystrigol. [Copyright &y& Elsevier]

The article presents a study on the germination stimulants for root parasitic plants from Linum usitatissimum L. or flax. It states that the root exudate of flax has 6 strigolactones as suggested by analyses using liquid chromatography-tandem mass spectrometry and gas chromatography mass spectrometry. It notes the orobanchol and orobanchyl acetate as the two strigolactones reveales on the analyses. After purification, the two were identified as 7-oxoorobanchol and 7-oxoorobanchyl acetate.

Abstract: A germination stimulant, fabacyl acetate, was purified from root exudates of pea (Pisum sativum L.) and its structure was determined as ent-2′-epi-4a,8a-epoxyorobanchyl acetate [(3aR,4R,4aR,8bS,E)-4a,8a-epoxy-8,8-dimethyl-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yloxy)methylene)-2-oxo-3,3a,4,5,6,7,8,8b-decahydro-2H-indeno[1,2-b]furan-4-yl acetate], by 1D and 2D NMR spectroscopic, ESI- and EI–MS spectrometric, X-ray crystallographic analyses, and by comparing the 1H NMR spectroscopic data and relative retention times (RR t) in LC–MS and GC–MS with those of synthetic standards prepared from (+)-orobanchol and (+)-2′-epiorobanchol. The 1H NMR spectroscopic data and RR t of fabacyl acetate were identical with those of an isomer prepared from (+)-2′-epiorobanchol except for the opposite sign in CD spectra. This is the first natural ent-strigolactone containing an epoxide group. Fabacyl acetate was previously detected in root exudates of other Fabaceae plants including faba bean (Vicia faba L.) and alfalfa (Medicago sativa L.). [Copyright &y& Elsevier]

Abstract: Alectrol, a germination stimulant for root parasitic plants, was purified from root exudates of red clover (Trifolium pratense L.) and identified as a strigolactone, (+)-orobanchyl acetate [(3aS,4S,8bS,E)-8,8-dimethyl-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yloxy)methylene)-2-oxo-3,3a,4,5,6,7,8,8b-octahydro-2H-indeno[1,2-b]furan-4-yl acetate], by 1D and 2D NMR spectroscopy and ESI- and EI-MS spectrometry. Orobanchyl acetate afforded an [M–42]+ ion in EI-MS and thus had been recognized as an isomer of strigol. Orobanchyl acetate was detected in root exudates of soybean (Glycine max L.) and cowpea (Vigina unguiculata L.) along with orobanchol. [Copyright &y& Elsevier]

Orobanche minor is a parasitic weed that attaches to the roots of red clover ( Trifolium pratense) and a number of other broad-leaved plant species in the Pacific Northwest USA. Orobanche minor seed must be stimulated by host plant exudates for germination and attachment to occur. However, plant species called false-hosts can stimulate parasitic seed germination without attachment. These species could be utilized as trap crops to reduce the amount of parasitic seed in infested soil. Wheat ( Triticum aestivum), was found to be a false-host of O. minor; therefore, growth chamber, glasshouse and field soil experiments were conducted to evaluate the effect of six soft white winter wheats ( T. aestivum), one durum wheat ( Triticum turgidum), and one triticale ( Triticale hexaploide) on O. minor germination. In growth chamber experiments, wheat and triticale induced 20–70% of O. minor seeds to germinate. In glasshouse studies, O. minor attachment was minimal on red clover plants grown in pots previously planted to wheat or triticale. In pots that did not receive a false-host treatment, red clover plants averaged 4.2 O. minor attachments per plant. Red clover plants also had fewer O. minor attachments when grown in field soil taken from the plots where wheat or triticale were grown compared with plants grown in soil where no wheat or triticale were previously grown. Our results demonstrate that wheat may have the potential to be effectively integrated into an O. minor management system. [ABSTRACT FROM AUTHOR]

Presents a study on the isolation and characterization of a cDNA encoding phytochrome A (PHYA) in the non-photosynthetic parasitic plant, Orobanche minor Sm. Presence of a PHYA homology in the holoparasite; Identification of the amino acid sequence with PHYA in Arabidopsis; Importance of the phytochromes in the regulation of a wide range of development responses in plants.

The article discusses the process of purification and characterization of a β-Glucosidase from Orobanche minor, a root parasitic angiosperm. The process involved a setting with an optimum potential of hydrogen (pH) and a temperature for enzyme activity of 5 degrees Celsius and 50 degrees Celsius. It was found that β-Glucosidase was stable up to 50 degrees Celsius at pH 4.0-10.0.

Strigolactones (SLs), a group of plant hormones, induce germination of root-parasitic plants and inhibit shoot branching in many plants. Shoot branching is an important trait that affects the number and quality of flowers and fruits. Root-parasitic plants, such as Phelipanche spp., infect tomato roots and cause economic damage in Europe and North Africa—hence why resistant tomato cultivars are needed. In this study, we found carotenoid cleavage dioxygenase 8-defective mutants of Micro-Tom tomato (slccd8) by the "targeting induced local lesions in genomes" (TILLING) method. The mutants showed excess branching, which was suppressed by exogenously applied SL. Grafting shoot scions of the slccd8 mutants onto wild-type (WT) rootstocks restored normal branching in the scions. The levels of endogenous orobanchol and solanacol in WT were enough detectable, whereas that in the slccd8 mutants were below the detection limit of quantification analysis. Accordingly, root exudates of the slccd8 mutants hardly stimulated seed germination of root parasitic plants. In addition, SL deficiency did not critically affect the fruit traits of Micro-Tom. Using a rhizotron system, we also found that Phelipanche aegyptiaca infection was lower in the slccd8 mutants than in wild-type Micro-Tom because of the low germination. We propose that the slccd8 mutants might be useful as new tomato lines resistant to P. aegyptiaca. [ABSTRACT FROM AUTHOR]