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Publications

Hause, B.; Maier, W.; Miersch, O.; Kramell, R.; Strack, D.; Induction of Jasmonate Biosynthesis in Arbuscular Mycorrhizal Barley Roots Plant Physiol. 130, 1213-1220, (2002) DOI: 10.1104/pp.006007

Colonization of barley (Hordeum vulgare cv Salome) roots by an arbuscular mycorrhizal fungus, Glomus intraradices Schenck & Smith, leads to elevated levels of endogenous jasmonic acid (JA) and its amino acid conjugate JA-isoleucine, whereas the level of the JA precursor, oxophytodienoic acid, remains constant. The rise in jasmonates is accompanied by the expression of genes coding for an enzyme of JA biosynthesis (allene oxide synthase) and of a jasmonate-induced protein (JIP23). In situ hybridization and immunocytochemical analysis revealed that expression of these genes occurred cell specifically within arbuscule-containing root cortex cells. The concomitant gene expression indicates that jasmonates are generated and act within arbuscule-containing cells. By use of a near-synchronous mycorrhization, analysis of temporal expression patterns showed the occurrence of transcript accumulation 4 to 6 d after the appearance of the first arbuscules. This suggests that the endogenous rise in jasmonates might be related to the fully established symbiosis rather than to the recognition of interacting partners or to the onset of interaction. Because the plant supplies the fungus with carbohydrates, a model is proposed in which the induction of JA biosynthesis in colonized roots is linked to the stronger sink function of mycorrhizal roots compared with nonmycorrhizal roots.
Publications

Vierheilig, H.; Maier, W.; Wyss, U.; Samson, J.; Strack, D.; Piché, Y.; Cyclohexenone derivative- and phosphate-levels in split-root systems and their role in the systemic suppression of mycorrhization in precolonized barley plants J. Plant Physiol. 157, 593-599, (2000) DOI: 10.1016/S0176-1617(00)80001-2

In a split-root system root colonization by the arbuscular mycorrhizal fungus Glomus mosseae on one side is reduced when roots on the other side are already colonized by G. mosseae. Root colonization by arbuscular mycorrhizal fungi enhances the P-status of plants, thus the observed suppressional effect on further root colonization in precolonized barley plants could be P-level regulated. Split-root systems allow to separate plant mediated P-effects on root colonization by arbuscular mycorrhizal fungi from direct P-effects on arbuscular mycorrhizal fungi. By adding a KH2PO4-solution to one side of the split-root system of non-mycorrhizal control plants, higher P-levels were obtained as in split-root systems of G. mosseae precolonized plants. Subsequent inoculation with G. mosseae of the P-supplied and the precolonized plants resulted in an inhibition of root colonization in the precolonized plants, but not in the P-supplied plants, discarding the enhanced P-level as the responsible factor for the observed suppression. Cyclohexenone derivatives are secondary plant compounds only found in roots of mycorrhizal plants. Analysis of cyclohexenone derivatives in mycorrhizal and non-mycorrhizal roots in split-root systems revealed that cyclohexenone derivatives can be detected in mycorrhizal roots, but not in non-mycorrhizal roots of mycorrhizal plants. The presented results show clearly that cyclohexenone derivatives are not systemically accumulated and that the P-levels are not the responsible factors for the observed systemic suppression of mycorrhization in roots of precolonized barley plants.
Publications

Vierheilig, H.; Gagnon, H.; Strack, D.; Maier, W.; Accumulation of cyclohexenone derivatives in barley, wheat and maize roots in response to inoculation with different arbuscular mycorrhizal fungi Mycorrhiza 9, 291-293, (2000) DOI: 10.1007/PL00009994

Glomus intraradices, Glomus mosseae, and Gigaspora rosea leads to the accumulation of cyclohexenone derivatives. Mycorrhizal roots of all plants accumulate in response to all three fungi blumenin [9-O-(2′-O-glucuronosyl)-β-glucopyranoside of 6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one], 13-carboxyblumenol C 9-O-gentiobioside, nicoblumin [9-O-(6′-O-β-glucopyranosyl)-β-glucopyranoside of 13-hydroxy-6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one] and another, as yet unidentified, cyclohexenone derivative. The accumulation of all four compounds in three tested mycorrhizal plants colonized by the three arbuscular mycorrhizal fungi indicates no fungus-specific induction of these compounds.
Publications

Maier, W.; Schmidt, J.; Nimtz, M.; Wray, V.; Strack, D.; Secondary products in mycorrhizal roots of tobacco and tomato Phytochemistry 54, 473-479, (2000) DOI: 10.1016/S0031-9422(00)00047-9

Colonization of the roots of various tobacco species and cultivars (Nicotiana glauca Grah., N. longiflora Cav., N. rustica L., N. tabacum L., N. tabacum L. cv. Samsun NN, N. sanderae hort. Sander ex Wats.) as well as tomato plants (Lycopersicon esculentum L. cv. Moneymaker) by the arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith resulted in the accumulation of several glycosylated C13 cyclohexenone derivatives. Eight derivatives were isolated from the mycorrhizal roots by preparative high performance liquid chromatography (HPLC) and spectroscopically identified (MS and NMR) as mono-, di- and triglucosides of 6-(9-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one and monoglucosides of 6-(9-hydroxybutyl)-1,5-dimethyl-4-cyclohexen-3-one-1-carboxylic acid and 6-(9-hydroxybutyl)-1,1-dimethyl-4-cyclohexen-3-one-5-carboxylic acid. In contrast to the induced cyclohexenone derivatives, accumulation of the coumarins scopoletin and its glucoside (scopolin) in roots of N. glauca Grah. and N. tabacum L. cv. Samsun NN, was markedly suppressed.
Publications

Maier, W.; Schmidt, J.; Wray, V.; Walter, M. H.; Strack, D.; The arbuscular mycorrhizal fungus, Glomus intraradices , induces the accumulation of cyclohexenone derivatives in tobacco roots Planta 207, 620-623, (1999) DOI: 10.1007/s004250050526

Tobacco (Nicotiana tabacum L.) plants were grown with and without the arbuscular mycorrhizal fungus, Glomus intraradices Schenk & Smith. High-performance liquid chromatographic analyses of methanolic extracts from mycorrhizal and non-mycorrhizal tobacco roots revealed marked fungus-induced changes in the patterns of UV-detectable products. The UV spectra of these products, obtained from an HPLC photodiode array detector, indicated the presence of several blumenol derivatives. The most predominant compound among these derivatives was spectroscopically identified as 13-hydroxyblumenol C 9-O-gentiobioside (“nicoblumin”), i.e. the 9-O-(6′-O-β-glucopyranosyl)-β-glucopyranoside of 13-hydroxy-6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one, a new natural product. This is the first report on the identification of blumenol derivatives in mycorrhizal roots of a non-gramineous plant.
Publications

Fester, T.; Maier, W.; Strack, D.; Accumulation of secondary compounds in barley and wheat roots in response to inoculation with an arbuscular mycorrhizal fungus and co-inoculation with rhizosphere bacteria Mycorrhiza 8, 241-246, (1999) DOI: 10.1007/s005720050240

Colonization of Hordeum vulgare L. cv. Salome (barley)and Triticum aestivum L. cv. Caprimus (wheat) roots by the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith leads to de novo synthesis of isoprenoid cyclohexenone derivatives with blumenin [9-O-(2′-O-β-glucuronosyl)-β-glucopyranoside of 6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one] as the major constituent and to transient accumulation of hydroxycinnamate amides (4-coumaroylagmatine and -putrescine). Accumulation of these compounds in mycorrhizal wheat roots started 2 weeks after sowing together with the onset of arbuscule formation and proceeded with mycorrhizal progression. Highest levels were reached in 3- to 4-week-old secondary roots (root branches of first and higher order) characterized by the formation of vesicles. In the final developmental stages, the fungus produced massive amounts of spores, enclosing the stele of older root parts (older than 5 weeks) characterized by cortical death. In these root parts, the secondary compounds were detected in trace amounts only, indicating that they were located in the cortical tissues. Some rhizosphere bacteria tested, i.e. Agrobacterium rhizogenes, Pseudomonas fluorescens, and Rhizobium leguminosarum, markedly stimulated both fungal root colonization and blumenin accumulation, thus, acting as mycorrhiza-helper bacteria (MHB). Application of blumenin itself strongly inhibited fungal colonization and arbuscule formation at early stages of mycorrhiza development. This was associated with a markedly reduced accumulation of the hydroxycinnamate amides 4-coumaroylputrescine and -agmatine. The results suggest that both the isoprenoid and the phenylpropanoid metabolism are closely linked to the developmental stage and the extent of fungal colonization. Their possible involvement in the regulation of mycorrhiza development is discussed.
Publications

Maier, W.; Schneider, B.; Strack, D.; Biosynthesis of sesquiterpenoid cyclohexenone derivatives in mycorrhizal barley roots proceeds via the glyceraldehyde 3-phosphate/pyruvate pathway Tetrahedron Lett. 39, 521-524, (1998) DOI: 10.1016/S0040-4039(97)10673-6

Incorporation of [1-13C]- and [U-13C6]glucose indicates that the biosynthesis of sesquiterpenoid cyclohexenone derivatives in mycorrhizal barley roots proceeds via the glyceraldehyde 3-phosphate/pyruvate non-mevalonate pathway.Incorporation of label from [1-13C]glucose (•) and [U-13C6]glucose ( − ) into the aglycon part (blumenol C) of blumenin indicates that in barley roots the arbuscular mycorrhizal fungus Glomus intraradices induces the glyceraldehyde 3-phosphate/pyruvate non-mevalonate pathway leading to sesquiterpenoid cyclohexenone derivatives.
Publications

Peipp, H.; Maier, W.; Schmidt, J.; Wray, V.; Strack, D.; Arbuscular mycorrhizal fungus-induced changes in the accumulation of secondary compounds in barley roots Phytochemistry 44, 581-587, (1997) DOI: 10.1016/S0031-9422(96)00561-4

Hordeum vulgare (barley) was grown in a defined nutritional medium with and without the arbuscular mycorrhizal fungus Glomus intraradices. HPLC of methanolic extracts from the roots of mycorrhized and non-mycorrhized plants revealed fungus-induced accumulation of some secondary metabolites. These compounds were isolated and identified by spectroscopic methods (NMR, MS) to be the hydroxycinnamic acid amides N-(E)-4-coumaroylputrescine, N-(E)-feruloylputrescine, N-(E)-4-coumaroylagmatine and N-(E)-feruloylagmatine, exhibiting a transient accumulation, and the cyclohexenone derivatives 4-(3-O-β-glucopyranosyl-butyl)-3-(hydroxymethyl)-5,5-dimethyl-2-cyclohexen-1-one and 4-{3-O-[(2′-O-β-glucuronosyl)-β-glucopyranosyl]-butyl}-3,5,5-trimethyl-2-cyclohexen-1-one (blumenin), exhibiting a continuous accumulation. A third cyclohexenone derivative, 4-{3-O-[(2′-O-β-glucuronosyl)-β-glucopyranosyl]-1-butenyl}-3,5,5-trimethyl-2-cyclohexen-1-one, was detectable only in minute amounts. It is suggested that accumulation of the amides in early developmental stages of barley mycorrhization reflects initiation of a defence response. However, the continuous accumulation of the cyclohexenone derivatives, especially blumenin, seems to correlate with the establishment of a functional barley mycorrhiza.
Publications

Maier, W.; Hammer, K.; Dammann, U.; Schulz, B.; Strack, D.; Accumulation of sesquiterpenoid cyclohexenone derivatives induced by an arbuscular mycorrhizal fungus in members of the Poaceae Planta 202, 36-42, (1997) DOI: 10.1007/s004250050100

Sixty one members of the Poaceae, including various cereals, were grown in defined nutrient media with and without the arbuscular mycorrhizal (AM) fungus, Glomus intraradices Schenk & Smith. The roots of all species investigated were colonized by the AM fungus, however, to different degrees and independent of their systematic position. High-performance liquid chromatographic analyses of methanolic extracts from the roots of mycorrhizal and nonmycorrhizal species revealed dramatic changes in the patterns of UV-detectable products along with a widespread occurrence of AM-fungus-induced accumulation of sesquiterpenoid cyclohexenone derivatives. The latter occur most often in the tribes Poeae, Triticeae and Aveneae. Some additional control experiments on plant infection with pathogens (Gaeumannomyces graminis) and Drechslera sp.) or an endophyte (Fusarium sp.), as well as application of abiotic stress, proved that the metabolism of these terpenoids is part of a response pattern of many gramineous roots in their specific reaction to AM fungal colonization.
Publications

Maier, W.; Baumert, A.; Gröger, D.; Partial Purification and Characterization of S-Adenosyl-L- Methionine:Anthranilic Acid N-Methyltransferase from Ruta Cell Suspension Cultures J. Plant Physiol. 145, 1-6, (1995) DOI: 10.1016/S0176-1617(11)81837-7

S-Adenosyl-L-methionine: anthranilic acid N-methyltransferase has been purified from cell suspensioncultures of Ruta graveolens by using a combination of gel filtration and ion exchange chromatography. This particular N-methyltransferase, which catalyzes the first pathway specific step in acridone alkaloid biosynthesis, was purified 370-fold. The enzyme has a pH optimum of 7.8, a Mr of 70,000 on gel filtration and a Mr of 62,000 on SDS-PAGE. The properties, the substrate specificity and the Michaelis-Menten constants of the purified enzyme were determined. The anthranilic acid specific N-methyltransferase is strongly inhibited by S-adenosyl-L-homocysteine.
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