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Publikationen - Stoffwechsel- und Zellbiologie

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Publikation

Van Damme, E. J. M.; Hu, J.; Barre, A.; Hause, B.; Baggerman, G.; Rougé, P.; Peumans, W. J.; Purification, characterization, immunolocalization and structural analysis of the abundant cytoplasmic β-amylase from Calystegia sepium (hedge bindweed) rhizomes Eur. J. Biochem. 268, 6263-6273, (2001) DOI: 10.1046/j.0014-2956.2001.02584.x

An abundant catalytically active β‐amylase (EC 3.2.1.2) was isolated from resting rhizomes of hedge bindweed (Calystegia sepium ). Biochemical analysis of the purified protein, molecular modeling, and cloning of the corresponding gene indicated that this enzyme resembles previously characterized plant β‐amylases with regard to its amino‐acid sequence, molecular structure and catalytic activities. Immunolocalization demonstrated that the β‐amylase is exclusively located in the cytoplasm. It is suggested that the hedge bindweed rhizome β‐amylase is a cytoplasmic vegetative storage protein.
Publikation

Strack, D.; Fester, T.; Hause, B.; Walter, M. H.; Die arbuskuläre Mykorrhiza: Eine unterirdische Lebensgemeinschaft Biologie in unserer Zeit 31, 286-295, (2001) DOI: 10.1002/1521-415X(200109)31:5<286::AID-BIUZ286>3.0.CO;2-G

Pflanzen und bestimmte Pilze haben im Laufe ihrer Entwicklungsgeschichte „gelernt”︁, in einer engen Assoziation im Boden, der Mykorrhiza, eine äußerst erfolgreiche Symbiose miteinander einzugehen. Arbuskuläre Mykorrhizapilze helfen Pflanzen sich auf nährstoffarmen Böden ausreichend mit Wasser, Nährsalzen und Spurenelementen zu versorgen und fördern entscheidend Diversität und Produktivität von Pflanzengesellschaften. Darüber hinaus zeigen mykorrhizierte Pflanzen eine erhöhte Widerstandsfähigkeit gegen Pathogenbefall. Im Gegenzug „bezahlt”︁ die Pflanze den Pilz für diesen Gewinn mit Kohlenhydraten in Form einfacher Zucker (Glucose, Fructose). Durch manche Erfolge in der Erforschung der Mykorrhiza auf Metaboliten‐ und Genebene beginnen wir allmählich zu erahnen, wie komplex die molekularen Interaktionen dieser Symbiose sind. Es ist zu erwarten, dass das steigende Interesse an der Mykorrhizaforschung zu neuen Einsichten in die Strategien von Pflanzen und Pilzen in der Entwicklung mutualistisch‐symbiontischer Assoziationen führen wird.
Publikation

Strack, D.; Schliemann, W.; Bifunktionelle Polyphenoloxidasen: neuartige Funktionen in der Biosynthese pflanzlicher Farbstoffe Angew. Chem. 113, 3907-3911, (2001) DOI: 10.1002/1521-3757(20011015)113:20<3907::AID-ANGE3907>3.0.CO;2-J

Bisher war die Funktion der Polyphenoloxidasen (PPO) unklar. Inzwischen konnte aber gezeigt werden, dass eine Tyrosinase an der Betacyan‐Biosynthese des Portulakröschens (siehe Bild) und der Roten Rübe sowie eine Chalkon‐spezifische PPO an der Auronbildung in gelben Löwenmaulblüten beteiligt ist.
Publikation

Strack, D.; Schliemann, W.; Bifunctional Polyphenol Oxidases: Novel Functions in Plant Pigment Biosynthesis Angew. Chem. Int. Ed. 40, 3791-3794, (2001) DOI: 10.1002/1521-3773(20011015)40:20<3791::AID-ANIE3791>3.0.CO;2-T

Enzymes in search of a function, for polyphenol oxidases (PPOs), described as such, this situation has changed recently. A tyrosinase is involved in betacyanin biosynthesis in common portulaca (see picture) and red beet, and a chalcone‐specific PPO is responsible for the formation of aurones in yellow snapdragon flowers.
Publikation

Schliemann, W.; Cai, Y.; Degenkolb, T.; Schmidt, J.; Corke, H.; Betalains of Celosia argentea Phytochemistry 58, 159-165, (2001) DOI: 10.1016/S0031-9422(01)00141-8

The betalains of yellow, orange and red inflorescences of common cockscomb (Celosia argentea var. cristata) were compared and proved to be qualitatively identical to those of feathered amaranth (Celosia argentea var. plumosa). In addition to the known compounds amaranthin and betalamic acid, the structures of three yellow pigments were elucidated to be immonium conjugates of betalamic acid with dopamine, 3-methoxytyramine and (S)-tryptophan by various spectroscopic techniques and comparison to synthesized reference compounds; the latter two are new to plants. Among the betacyanins occurring in yellow inflorescences in trace amounts, the presence of 2-descarboxy-betanidin, a dopamine-derived betacyanin, has been ascertained. The detection of high dopamine concentration may be of toxicological relevance in use of yellow inflorescences as a vegetable and in traditional Chinese medicine, common uses for the red inflorescences of common cockscomb.The betaxanthins of two Celosia argentea varieties were identified as betalamic acid conjugates of dopamine (1), 3-methoxytyramine (2) and (S)-tryptophan.
Publikation

Milkowski, C.; Krampe, S.; Weirich, J.; Hasse, V.; Boles, E.; Breunig, K. D.; Feedback Regulation of Glucose Transporter Gene Transcription in Kluyveromyces lactis by Glucose Uptake J. Bacteriol. 183, 5223-5229, (2001) DOI: 10.1128/JB.183.18.5223-5229.2001

In the respirofermentative yeast Kluyveromyces lactis, only a single genetic locus encodes glucose transporters that can support fermentative growth. This locus is polymorphic in wild-type isolates carrying either KHT1and KHT2, two tandemly arranged HXT-like genes, or RAG1, a low-affinity transporter gene that arose by recombination between KHT1 andKHT2. Here we show that KHT1 is a glucose-induced gene encoding a low-affinity transporter very similar to Rag1p. Kht2p has a lower Km (3.7 mM) and a more complex regulation. Transcription is high in the absence of glucose, further induced by low glucose concentrations, and repressed at higher glucose concentrations. The response ofKHT1 and KHT2 gene regulation to high but not to low concentrations of glucose depends on glucose transport. The function of either Kht1p or Kht2p is sufficient to mediate the characteristic response to high glucose, which is impaired in akht1 kht2 deletion mutant. Thus, the KHTgenes are subject to mutual feedback regulation. Moreover, glucose repression of the endogenous β-galactosidase (LAC4) promoter and glucose induction of pyruvate decarboxylase were abolished in the kht1 kht2 mutant. These phenotypes could be partially restored by HXT gene family members fromSaccharomyces cerevisiae. The results indicate that the specific responses to high but not to low glucose concentrations require a high rate of glucose uptake.
Publikation

Lehmann, K.; Hause, B.; Altmann, D.; Köck, M.; Tomato Ribonuclease LX with the Functional Endoplasmic Reticulum Retention Motif HDEF Is Expressed during Programmed Cell Death Processes, Including Xylem Differentiation, Germination, and Senescence Plant Physiol. 127, 436-449, (2001) DOI: 10.1104/pp.010362

We have studied the subcellular localization of the acid S-like ribonuclease (RNase) LX in tomato (Lycopersicon esculentum Mill.) cells using a combination of biochemical and immunological methods. It was found that the enzyme, unexpectedly excluded from highly purified vacuoles, accumulates in the endoplasmic reticulum. The evidence that RNase LX is a resident of the endoplasmic reticulum (ER) is supported by an independent approach showing that the C-terminal peptide HDEF of RNase LX acts as an alternative ER retention signal in plants. For functional testing, the cellular distribution of chimeric protein constructs based on a marker protein, Brazil nut (Bertholletia excelsa) 2S albumin, was analyzed immunochemically in transgenic tobacco (Nicotiana tabacum) plants. Here, we report that the peptide motif is necessary and sufficient to accumulate 2S albumin constructs of both vacuolar and extracellular final destinations in the ER. We have shown immunochemically that RNase LX is specifically expressed during endosperm mobilization and leaf and flower senescence. Using immunofluorescence, RNase LX protein was detected in immature tracheary elements, suggesting a function in xylem differentiation. These results support a physiological function of RNase LX in selective cell death processes that are also thought to involve programmed cell death. It is assumed that RNase LX accumulates in an ER-derived compartment and is released by membrane disruption into the cytoplasma of those cells that are intended to undergo autolysis. These processes are accompanied by degradation of cellular components supporting a metabolic recycling function of the intracellular RNase LX.
Publikation

Hao, Q.; Van Damme, E. J. M.; Hause, B.; Barre, A.; Chen, Y.; Rougé, P.; Peumans, W. J.; Iris Bulbs Express Type 1 and Type 2 Ribosome-Inactivating Proteins with Unusual Properties Plant Physiol. 125, 866-876, (2001) DOI: 10.1104/pp.125.2.866

Two closely related lectins from bulbs of the Dutch iris (Iris hollandica var. Professor Blaauw) have been isolated and cloned. Both lectins, called Iris agglutinin b and Iris agglutinin r, possess N-glycosidase activity and share a high sequence similarity with previously described type 2 ribosome-inactivating proteins (RIP). However, these lectins show only 57% to 59% sequence identity to a previously characterized type 1 RIP from iris, called IRIP. The identification of the iris lectins as type 2 RIP provides unequivocal evidence for the simultaneous occurrence of type 1 and type 2 RIP in iris bulbs and allowed a detailed comparison of type 1 and type 2 RIP from a single plant, which provides further insight into the molecular evolution of RIP. Binding studies and docking experiments revealed that the lectins exhibit binding activity not only toward Gal/N-acetylgalactosamine, but also toward mannose, demonstrating for the first time that RIP-binding sites can accommodate mannose.
Publikation

Fester, T.; Strack, D.; Hause, B.; Reorganization of tobacco root plastids during arbuscule development Planta 213, 864-868, (2001) DOI: 10.1007/s004250100561

In the present paper we analyzed plastid populations labeled by the green fluorescent protein in non-mycorrhizal and mycorrhizal roots of tobacco (Nicotiana tabacum L.). We show by confocal laser scanning microscopy (i) a dramatic increase in these plastids in mycorrhizal roots and (ii) the formation of dense plastid networks covering the symbiotic interface of the arbuscular mycorrhiza, the arbuscule. These cytological observations point to an important role of root cortical cell plastids in the functioning of arbuscular mycorrhizal symbiosis.
Publikation

Cai, Y.; Sun, M.; Schliemann, W.; Corke, H.; Chemical Stability and Colorant Properties of Betaxanthin Pigments from Celosia argentea J. Agr. Food Chem. 49, 4429-4435, (2001) DOI: 10.1021/jf0104735

The chemical stability and colorant properties of three betaxanthins recently identified from Celosia argentea varieties were evaluated. Lyophilized betaxanthin powders from yellow inflorescences of Celosia exhibited bright yellow color and high color purity with strong hygroscopicity. The aqueous solutions containing these betaxanthins were bright yellow in the pH range 2.2−7.0, and they were most stable at pH 5.5. The betaxanthins in a model system (buffer) were susceptible to heat, and found to be as unstable as red betacyanins (betanin and amaranthine) at high temperatures (>40 °C), but more stable at 40 °C with the exclusion of light and air. The three betaxanthins had slightly higher pigment retention than amaranthine/isoamaranthine in crude extracts at 22 °C, as verified by HPLC analysis. Lyophilized betaxanthins had much better storage stability (mean 95.0% pigment retention) than corresponding aqueous solutions (14.8%) at 22 °C after 20 weeks. Refrigeration (4 °C) significantly increased pigment retention of aqueous betaxanthins to 75.5%.
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