Rudy Vergauwen

Rudy Vergauwen
KU Leuven | ku leuven · Department of Biology

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40
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Publications

Publications (40)
Article
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The metabolism of sucrose is of crucial importance for life on Earth. In plants, enzymes called invertases split sucrose into glucose and fructose, contributing to the regulation of metabolic fluxes. Invertases differ in their localization and pH optimum. Acidic invertases present in plant cell walls and vacuoles belong to glycoside hydrolase famil...
Article
A liquid chromatography-mass spectrometry (LC-MS) library is presented containing the relative retention times of 28 fructan oligomers and MS² spectra of 18 of them. It includes the main representatives of all fructan classes occurring in nature and with a degree of polymerization between three and five. This library enables a rapid and unambiguous...
Article
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As the first organ in plants to sense water-deficit in the soil, roots have important roles for improving crop adaption to water limited environments. Stem water soluble carbohydrates (WSC) are a major carbon source for grain filling under drought conditions. The contributions of root WSC during grain filling under drought has not been revealed. Wh...
Article
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from raffinose family oligosaccharide to fructan metabolism in leaves of boxtree (Buxus sempervirens) Wim Van den Ende1,* Marlies Coopman1, Rudy Vergauwen1, André Van Laere1 1 KU Leuven, Laboratory of Molecular Plant Biology, Institute of Botany and Microbiology, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium * Correspondence: Wim Van den Ende, La...
Article
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Fructans are important vacuolar reserve carbohydrates with drought, cold, ROS and general abiotic stress mediating properties. They occur in 15% of all flowering plants and are believed to display health benefits as a prebiotic and dietary fiber. Fructans are synthesized by specific fructosyltransferases and classified based on the linkage type bet...
Article
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In wheat, stem water soluble carbohydrates (WSC), composed mainly of fructans, are the major carbon sources for grain filling during periods of decreasing photosynthesis or under drought stress after anthesis. Here, in a field drought experiment, WSC levels and associated enzyme activities were followed in different stem segments (peduncle, penulti...
Article
Full-text available
The water-soluble carbohydrates (WSC) glucose, fructose and sucrose are well-known to the great public, but fructan represents another type of WSC that deserves more attention given their prebiotic and immunomodulatory properties in the food context. Although the occurrence of inulin-type fructo-oligosaccharides (FOS) was proposed in the fruit of s...
Article
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Wheat kernels contain fructans, fructose based oligosaccharides with prebiotic properties, in levels between 2 and 35 weight % depending on the developmental stage of the kernel. To improve knowledge on the metabolic pathways leading to fructan storage and degradation, carbohydrate fluxes occurring during durum wheat kernel development were analyze...
Article
In wheat stems, the levels of fructan-dominated water-soluble carbohydrates (WSC) do not always correlate well with grain yield. Field drought experiments were carried out to further explain this lack of correlation. Wheat (Triticum aestivum) varieties, Westonia, Kauz and c. 20 genetically diverse double haploid (DH) lines derived from them were in...
Article
Although fructans play a crucial role in wheat kernel development, their metabolism during kernel maturation is far from being understood. In this study, all major fructan-metabolizing enzymes together with fructan content, fructan degree of polymerization and the presence of fructan oligosaccharides were examined in developing wheat kernels (Triti...
Article
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Flooding stress is known to affect root growth and sugar metabolism in plants, but data are crucially missing for Cichorium intybus which stores inulin in its tap root. The aim of the present study was to quantify the impact of recurrent episodes of flooding stress on plant growth, water status, photosynthesis and sugar metabolism in relation to in...
Article
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Cell wall invertases (cwINVs), with a high affinity for the cell wall, are fundamental enzymes in the control of plant growth, development and carbon partitioning. Most interestingly, defective cwINVs have been described in several plant species. Their highly attenuated sucrose hydrolyzing capacity is due to the absence of Asp239 and Trp47 homologu...
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In contrast to the well-documented roles of its mono- and bisphosphate esters, the occurrence of free sedoheptulose in plant tissues remains a matter of conjecture. The present work sought to determine the origin of sedoheptulose formation in planta, as well as its physiological importance. Elevated CO2 and sucrose induction experiments were used t...
Article
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Recent in vitro, in vivo, and theoretical experiments strongly suggest that sugar-(like) molecules counteract oxidative stress by acting as genuine reactive oxygen species (ROS) scavengers. A concept was proposed to include the vacuole as a part of the cellular antioxidant network. According to this view, sugars and sugar-like vacuolar compounds wo...
Article
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Background and AimsThere is a great need to search for natural compounds with superior prebiotic, antioxidant and immunostimulatory properties for use in (food) applications. Raffinose family oligosaccharides (RFOs) show such properties. Moreover, they contribute to stress tolerance in plants, acting as putative membrane stabilizers, antioxidants a...
Article
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Root chicory (Cichorium intybus var. sativum) is a cash crop cultivated for inulin production in Western Europe. This plant can be exposed to severe water stress during the last 3 months of its 6-month growing period. The aim of this study was to quantify the effect of a progressive decline in water availability on plant growth, photosynthesis, and...
Article
An improved method for the measurement of fructans in wheat grains is presented. A mild acid treatment is used for fructan hydrolysis, followed by analysis of the released glucose and fructose with high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Not only the amount of fructose set free from fructans bu...
Article
Fructans play important roles as reserve carbohydrates and stress protectants in plants, and additionally serve as prebiotics with emerging antioxidant properties. Various fructan types are synthesized by an array of plant fructosyltransferases belonging to family 32 of the glycoside hydrolases (GH32), clustering together with GH68 in Clan-J. Here,...
Article
Remobilization of stored carbohydrates in the stem of wheat plants is an important contributor to grain filling under drought stress (DS) conditions. A massive screening on Iranian wheat cultivars was performed based on stem dry weight changes under well-watered and DS conditions. Two cultivars, Shole and Crossed Falat Hamun (CFH), with different f...
Article
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About 15% of flowering plants accumulate fructans. Inulin-type fructans with β(2,1) fructosyl linkages typically accumulate in the core eudicot families (e.g. Asteraceae), while levan-type fructans with β(2,6) linkages and branched, graminan-type fructans with mixed linkages predominate in monocot families. Here, we describe the unexpected finding...
Article
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Fructosyltransferases (FTs) synthesize fructans, fructose polymers accumulating in economically important cool-season grasses and cereals. FTs might be crucial for plant survival under stress conditions in species in which fructans represent the major form of reserve carbohydrate, such as perennial ryegrass (Lolium perenne). Two FT types can be dis...
Article
A third fructan exohydrolase isoform (1-FEHw3) was purified from wheat stems by a combination of ammonium sulfate precipitation, ConA affinity and ion-exchange chromatography. Homogeneity of the preparation was indicated by the presence of a single band (70 kDa) after SDS-PAGE. The enzyme hydrolyzed mainly beta2-1 linkages in fructans and was inhib...
Article
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Fructans, typically reserve carbohydrates, may also fulfil other more specific roles in plants. It has been convincingly demonstrated that fructan hydrolysis contributes to osmoregulation during flower opening in the monocot species Hemerocallis. We report that a massive breakdown of inulin-type fructans in the petals of Campanula rapunculoides L....
Article
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Inulin-type fructans are the simplest and most studied fructans and have become increasingly popular as prebiotic health-improving compounds. A natural variation in the degree of polymerization (DP) of inulins is observed within the family of the Asteraceae. Globe thistle (Echinops ritro), artichoke (Cynara scolymus), and Viguiera discolor biosynth...
Article
Inulin-type fructans are stored in the tuberous roots of the Brazilian cerrado plant Viguiera discolor Baker (Asteraceae). In Cynara scolymus (artichoke) and Echinops ritro (globe thistle), the fructans have a considerably higher degree of polymerization (DP) than in Cichorium intybus (chicory) and Helianthus tuberosus (Jerusalem artichoke). It was...
Article
Cereals accumulate graminan-type fructans which are subject to stress-related degradation by fructan 1-exohydrolases (1-FEHs) and fructan 6-exohydrolases (6-FEHs). To find new FEH genes related to freezing tolerance, a cold-hardened wheat crown cDNA library was screened. Here we report the cloning, purification and characterization of two novel 6-k...
Article
The genome of Arabidopsis thaliana contains six putative cell-wall type invertase genes (AtcwINV1-6). Heterologous expression of AtcwINV1, 3 and 6 cDNAs in Pichia pastoris revealed that the enzymes encoded by AtcwINV3 and 6 did not show invertase activity. Instead, AtcwINV3 is a 6-FEH and AtcwINV6 is a fructan exohydrolase (FEH) that can degrade bo...
Article
About 15% of flowering plant species synthesize fructans. Fructans serve mainly as reserve carbohydrates and are subject to breakdown by plant fructan exohydrolases (FEHs), among which 1-FEHs (inulinases) and 6-FEHs (levanases) can be differentiated. This paper describes the unexpected finding that 6-FEHs also occur in plants that do not synthesize...
Article
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Remarkably, within the Asteraceae, a species-specific fructan pattern can be observed. Some species such as artichoke (Cynara scolymus) and globe thistle (Echinops ritro) store fructans with a considerably higher degree of polymerization than the one observed in chicory (Cichorium intybus) and Jerusalem artichoke (Helianthus tuberosus). Fructan:fru...
Article
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Graminan-type fructans are temporarily stored in wheat (Triticum aestivum) stems. Two phases can be distinguished: a phase of fructan biosynthesis (green stems) followed by a breakdown phase (stems turning yellow). So far, no plant fructan exohydrolase enzymes have been cloned from a monocotyledonous species. Here, we report on the cloning, purific...
Article
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Inulin type fructan was detected in all vegetative organs of Campanula rapunculoides L. plants. All flower parts contained fructan at some developmental stage. A steady decrease was found in sepals during development. Petals, however, stored fructan in the bud stage. A rapid breakdown during opening of the flower resulted in high concentrations of...
Article
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Sucrose:sucrose 1-fructosyl transferase (1-SST) is the key enzyme initiating fructan synthesis in Asteraceae. Using reverse transcriptase-PCR, we isolated the cDNA for 1-SST from Taraxacum officinale. The cDNA-derived amino acid sequence showed very high homology to other Asteracean 1-SSTs (Cichorium intybus 86%, Cynara scolymus 82%, Helianthus tub...
Article
Leek was analyzed for its chitinolytic activity. Chitinase (EC 3.2.1.14) activity could be detected in all plant parts except the inner white leaf sheaths. Extremely high levels were found in tepals and anthers after anthesis and in the upper white part of the peripheral leaf sheaths. Most of the activity was retained on a chitin column, but values...
Article
Six chitinases (EC 3.2.1.14) were purified from salicylate-treated leek (Allium porrum L.). They all strongly bind to chitin and can roughly be divided into two groups. One group has blocked N-termini, is completely inhibited by 1 mM AgNO3, has a relatively narrow pH optimum, a temperature optimum of 40°C and cannot degrade the tetramer of chitin....
Article
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Starvation of Saccharomyces cerevisiae cells for specific nutrients such as nitrogen, phosphate or sulphate causes arrest in the G1 phase of the cell cycle at a specific point called 'start'. Re-addition of different nitrogen sources, phosphate or sulphate to such starved cells causes activation of trehalase within a few minutes. Nitrogen-source- a...

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