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Eckhard Leistner

Publications and source records attributed to Eckhard Leistner.

13 recordsLinked to original sources
PubMed2006

Analysis of the Arabidopsis rsr4-1/pdx1-3 mutant reveals the critical function of the PDX1 protein family in metabolism, development, and vitamin B6 biosynthesis.

Vitamin B6 represents a highly important group of compounds ubiquitous in all living organisms. It has been demonstrated to alleviate oxidative stress and in its phosphorylated form participates as a cofactor in >100 biochemical reactions. By means of a genetic approach, we have identified a novel mutant, rsr4-1 (for reduced sugar response), with aberrant root and leaf growth that requires supplementation of vitamin B6 for normal development. Cloning of the mutated gene revealed that rsr4-1 carries a point mutation in a member of the PDX1/SOR1/SNZ (for Pyridoxine biosynthesis protein 1/Singlet oxygen resistant 1/Snooze) family that leads to reduced vitamin B6 content. Consequently, metabolism is broadly altered, mainly affecting amino acid, raffinose, and shikimate contents and trichloroacetic acid cycle constituents. Yeast two-hybrid and pull-down analyses showed that Arabidopsis thaliana PDX1 proteins can form oligomers. Interestingly, the mutant form of PDX1 has severely reduced capability to oligomerize, potentially suggesting that oligomerization is important for function. In summary, our results demonstrate the critical function of the PDX1 protein family for metabolism, whole-plant development, and vitamin B6 biosynthesis in higher plants.

Amino Acid Sequence↗
PubMed2006

Polyketides from the marine-derived fungus Ascochyta salicorniae and their potential to inhibit protein phosphatases.

Chemical investigation of the marine fungus Ascochyta salicorniae led to the isolation of two new epimeric compounds, ascolactones A (1) and B (2), in addition to the structurally-related polyketides hyalopyrone (3), ascochitine (4), ascochital (5) and ascosalipyrone (6). The absolute configurations of the epimeric compounds 1 and 2 were assigned as (1R,9R) and (1S,9R), respectively, through simulation of the chiroptical properties using quantum-chemical CD calculations, and chiral GC-MS subsequent to oxidative cleavage (Baeyer-Villiger oxidation) of the side chain. In silico screening using the PASS software identified some of the A. salicorniae compounds (1-6) as potential inhibitors of protein phosphatases. Compound was found to inhibit the enzymatic activity of MPtpB with an IC(50) value of 11.5 microM.

Ascomycota↗
PubMed2006

Molecular characterization of a seed transmitted clavicipitaceous fungus occurring on dicotyledoneous plants (Convolvulaceae).

Ergoline alkaloids (syn. ergot alkaloids) are constituents of clavicipitaceous fungi (Ascomycota) and of one particular dicotyledonous plant family, the Convolvulaceae. While the biology of fungal ergoline alkaloids is rather well understood, the evolutionary and biosynthetic origin of ergoline alkaloids within the family Convolvulaceae is unknown. To investigate the possible origin of ergoline alkaloids from a plant-associated fungus, 12 endophytic fungi and one epibiotic fungus were isolated from an ergoline alkaloid-containing Convolvulaceae plant, Ipomoea asarifolia Roem. & Schult. Phylogenetic trees constructed from 18S rDNA genes as well as internal transcribed spacer (ITS) revealed that the epibiotic fungus belongs to the family Clavicipitaceae (Ascomycota) whereas none of the endophytic fungi does. In vitro and in vivo cultivation on intact plants gave no evidence that the endophytic fungi are responsible for the accumulation of ergoline alkaloids in I. asarifolia whereas the epibiotic clavicipitaceous fungus very likely is equipped with the genetic material to synthesize these compounds. This fungus resisted in vitro and in vivo cultivation and is seed transmitted. Several observations strongly indicate that this plant-associated fungus and its hitherto unidentified relatives occurring on different Convolvulaceae plants are responsible for the isolated occurrence of ergoline alkaloids in Convolvulaceae. This is the first report of an ergot alkaloid producing clavicipitaceous fungus associated with a dicotyledonous plant.

Ascomycota↗
PubMed2004

Elimination of ergoline alkaloids following treatment of Ipomoea asarifolia (Convolvulaceae) with fungicides.

Ergoline alkaloids are constituents of Clavicipitaceous fungi living on Poaceae plants. Ergoline alkaloids as well as volatile oil are also present in Ipomoea asarifolia Roem. & Schult (Convolvulaceae). Treatment of this plant with two fungicides (Folicur, Pronto Plus) eliminates the ergoline alkaloids but not the volatile oil. Elimination of ergoline alkaloids occurs concomitantly with loss of fungal hyphae associated with secretory glands on the upper leaf surface of the Ipomoea plant. Our observations suggest that accumulation of ergoline alkaloids in the Convolvulaceae may depend on the presence of a plant-associated fungus.

Ergolines↗
PubMed2004

Five novel Kitasatospora species from soil: Kitasatospora arboriphila sp. nov., K. gansuensis sp. nov., K. nipponensis sp. nov., K. paranensis sp. nov. and K. terrestris sp. nov.

A polyphasic study was carried out to establish the taxonomic positions of six strains isolated from diverse soil samples and provisionally assigned to the genus Kitasatospora. The isolates were found to have chemical and morphological properties consistent with their classification as Kitasatospora strains. Direct 16S rRNA gene sequence data confirmed the taxonomic position of the strains following the generation of phylogenetic trees by using three tree-making algorithms. Five of the isolates were considered to merit species status using complementary genotypic and phenotypic data. These organisms were designated Kitasatospora arboriphila sp. nov. (HKI 0189(T)=2291-120(T)=DSM 44785(T)=NCIMB 13973(T)), Kitasatospora gansuensis sp. nov. (HKI 0314(T)=2050-015(T)=DSM 44786(T)=NCIMB 13974(T)), Kitasatospora nipponensis sp. nov. (HKI 0315(T)=2148-013(T)=DSM 44787(T)=NCIMB 13975(T)), Kitasatospora paranensis sp. nov. (HKI 0190(T)=2292-041(T)=DSM 44788(T)=NCIMB 13976(T)) and Kitasatospora terrestris sp. nov. (HKI 0186(T)=2293-012(T)=DSM 44789(T)=NCIMB 13977(T)). The remaining organism, isolate HKI 0316 (=2122-022=DSM 44790=NCIMB 13978), was considered to be a strain of Kitasatospora kifunensis on the basis of 16S rRNA gene sequence, DNA-DNA relatedness and phenotypic data.

Anti-Bacterial Agents↗
PubMed2004

Recent developments in the maytansinoid antitumor agents.

Maytansine and its congeners have been isolated from higher plants, mosses and from an Actinomycete, Actinosynnema pretiosum. Many of these compounds are antitumor agents of extraordinary potency, yet phase II clinical trials with maytansine proved disappointing. The chemistry and biology of maytansinoids has been reviewed repeatedly in the late 1970s and early 1980s; the present review covers new developments in this field during the last two decades. These include the use of maytansinoids as "warheads" in tumor-specific antibodies, preliminary metabolism studies, investigations of their biosynthesis at the biochemical and genetic level, and ecological issues related to the occurrence of such typical microbial metabolites in higher plants.

Animals↗
PubMed2003

Occurrence and non-detectability of maytansinoids in individual plants of the genera Maytenus and Putterlickia.

Individual plants belonging to different species of the family Celastraceae collected from their natural habitats in South Africa (Putterlickia verrucosa (E. Meyer ex Sonder) Szyszyl., Putterlickia pyracantha (L.) Szyszyl., Putterlickia retrospinosa van Wyk and Mostert) and Brazil (Maytenus ilicifolia Mart. ex Reiss., Maytenus evonymoides Reiss., Maytenus aquifolia Mart.) were investigated for the presence of maytansinoids and of maytansine, an ansamycin of high cytotoxic activity. Maytansinoids were not detectable in plants grown in Brazil. Analysis of plants growing in South Africa, however, showed clearly that maytansinoids were present in some individual plants but were not detectable in others. Molecular biological analysis of a Putterlickia verrucosa cell culture gave no evidence for the presence of the aminohydroxybenzoate synthase gene which is unique to the biosynthesis of aminohydroxybenzoate, a precursor of the ansamycins including maytansinoids. Moreover, this gene was not detectable in DNA extracted from the aerial parts of Putterlickia plants. In contrast, observations indicate that this gene may be present in microbes of the rhizosphere of Putterlickia plants. Our observations are discussed with respect to the possibility that the roots of Putterlickia plants may be associated with microorganisms which are responsible for the biosynthesis of maytansine or maytansinoids.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed2003

Kitasatospora putterlickiae sp. nov., isolated from rhizosphere soil, transfer of Streptomyces kifunensis to the genus Kitasatospora as Kitasatospora kifunensis comb. nov., and emended description of Streptomyces aureofaciens Duggar 1948.

A polyphasic study was undertaken to establish the taxonomic position of a rhizosphere isolate that had been assigned provisionally to the genus Kitasatospora. The organism, isolate F18-98(T), was found to have chemical and morphological properties that were consistent with its classification as a Kitasatospora strain. Direct 16S rDNA sequence data confirmed the taxonomic position of the strain, following the generation of phylogenetic trees by using three treeing algorithms. The organism formed a 16S rDNA subclade with Kitasatospora azatica and Streptomyces kifunensis, but was distinguished readily from the latter by using a combination of biochemical and physiological properties. Genotypic and phenotypic data show that strain F18-98(T) should be classified in the genus Kitasatospora as a novel species, for which the name Kitasatospora putterlickiae sp. nov. is proposed; the type strain has been deposited in culture collections as strain F18-98(T) (=DSM 44665(T)=NCIMB 13932(T)). It is also proposed that Streptomyces kifunensis should be transferred to the genus Kitasatospora as Kitasatospora kifunensis comb. nov. An emended description of Streptomyces aureofaciens Duggar 1948 is also given.

Actinomycetales↗
PubMed2002

New and bioactive compounds from Streptomyces strains residing in the wood of Celastraceae.

Wood from three different plants of the Celastraceae growing in their natural habitats in Brazil (Maytenus aquifolia Mart.) and South Africa [Putterlickia retrospinosa van Wyk and Mostert, P. verrucosa (E. Meyer ex Sonder) Szyszyl.] was established as a source of endophytic bacteria using a medium selective for actinomycetes. Two isolates were identified as Streptomyces setonii and S. sampsonii whereas two others were not assignable to any of the known Streptomyces species. They were preliminarily named Streptomyces Q21 and Streptomyces MaB-QuH-8. The latter strain produces a new chloropyrrol and chlorinated anthracyclinone. The chloropyrrol showed high activity against a series of multiresistent bacteria and mycobacteria.

Antibiotics, Antineoplastic↗
PubMed2002

The biosynthetic gene cluster of the maytansinoid antitumor agent ansamitocin from Actinosynnema pretiosum.

Maytansinoids are potent antitumor agents found in plants and microorganisms. To elucidate their biosynthesis at the biochemical and genetic level and to set the stage for their structure modification through genetic engineering, we have cloned two gene clusters required for the biosynthesis of the maytansinoid, ansamitocin, from a cosmid library of Actinosynnema pretiosum ssp. auranticum ATCC 31565. This is a rare case in which the genes involved in the formation of a secondary metabolite are dispersed in separate regions in an Actinomycete. A set of genes, asm22-24, asm43-45, and asm47, was identified for the biosynthesis of the starter unit, 3-amino-5-hydroxybenzoic acid (AHBA). Remarkably, there are two AHBA synthase gene homologues, which may have different functions in AHBA formation. Four type I polyketide synthase genes, asmA-D, followed by the downloading asm9, together encode eight homologous sets of enzyme activities (modules), each catalyzing a specific round of chain initiation, elongation, or termination steps, which assemble the ansamitocin polyketide backbone. Another set of genes, asm13-17, encodes the formation of an unusual "methoxymalonate" polyketide chain extension unit that, notably, seems to be synthesized on a dedicated acyl carrier protein rather than as a CoA thioester. Additional ORFs are involved in postsynthetic modifications of the initial polyketide synthase product, which include methylations, an epoxidation, an aromatic chlorination, and the introduction of acyl and carbamoyl groups. Tentative functions of several asm genes were confirmed by inactivation and heterologous expression.

Actinomycetales↗
PubMed1996

Bacterial production of transdihydroxycyclohexadiene carboxylates by metabolic pathway engineering.

Homochiral-cis-cyclohexa-3,5-diene-1,2-diols are important synthons. We found a way to produce trans-configured homochiral diols using recombinant Klebsiella pneumoniae 62-1. Transformation of this mutant (Phe- Trp- Tyr-) with plasmids carrying genes involved in chorismic and isochorismic acid metabolism leads to the production of either (+)-trans-(2S,3S)-2,3-dihydroxycyclohexa-4,6-dienecarboxylic acid or (-)-trans-(3R,4R)-3,4-dihydroxycyclohexa-1,5-dienecarboxylic acid, with a yield of 70 or 90 mg (1 culture broth)-1, respectively. The metabolic shift from one diene to the other is caused by a change in activity of isochorismate hydroxymutase and/or isochorismatase which in turn results from growth under iron deficiency or overexpression of genes (entC and/or entB) involved in chrismate metabolism.

Amino Acid Sequence↗