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Introduction
Publications
Publications (92)
To understand the growth response to drought, we performed a proteomics study in the leaf growth zone of maize (Zea mays L.) seedlings and functionally characterized the role of starch biosynthesis in the regulation of growth, photosynthesis and antioxidant capacity, using the shrunken‐2 mutant (sh2 ), defective in ADP‐glucose pyrophosphorylase.
Dr...
Map summarizing results of a Arabidopsis thaliana microarray experiment.Genes were individually examined in silico for function, structure and cellularcomponent. Of the 582 differentially regulated genes, 276 genes had predicted orexperimentally tested function annotated and were pasted on the map. Whenapplicable, proteins were grouped per function...
Cadmium (Cd) is a non-essential trace element that elicits oxidative stress. Plants respond to Cd toxicity via increasing their Cd-chelating and antioxidative capacities. They predominantly chelate Cd via glutathione (GSH) and phytochelatins (PCs), while antioxidative defence is mainly based on the use and recycling of both GSH and ascorbate (AsA),...
The Nicotiana tabacum agglutinin or Nictaba is a nucleocytoplasmic lectin that is expressed in tobacco after the plants have been exposed to jasmonate treatment or insect herbivory. Nictaba specifically recognizes GlcNAc residues. Recently, it was shown that Nictaba is interacting in vitro with the core histone proteins from calf thymus. Assuming t...
Background
Screening tests for gambiense sleeping sickness, such as the CATT/T. b. gambiense and a recently developed lateral flow tests, are hitherto based on native variant surface glycoproteins (VSGs), namely LiTat 1.3 and LiTat 1.5, purified from highly virulent trypanosome strains grown in rodents.
Methodology/Principal Findings
We have expre...
Plants respond to environmental stress by synthesizing a range of secondary metabolites for defense purposes. Here we report on the effect of chronic UV radiation on the accumulation of plant secondary metabolites in Arabidopsis thaliana leaves. In the natural environment, UV is a highly dynamic environmental parameter and therefore we hypothesized...
Objective: To evaluate the accuracy of a peptide, corresponding to the variant surface glycoprotein
(VSG) LiTat 1.5 amino acid (AA) sequence 268–281 and identified through alignment of monoclonal antibody selected mimotopes, for diagnosis of Trypanosoma brucei gambiense sleeping sickness.
Methods: A synthetic biotinylated peptide (peptide 1.5/268–2...
Lipoxygenases (LOXes, EC 1.13.11.12) are involved in growth, development and responses to stress. Earlier results suggested a role in stress generation, signalling and/or responses when Arabidopsis thaliana is exposed to cadmium (Cd), and expression of the cytosolic LOX1 was highly upregulated in the roots after Cd exposure. To investigate the invo...
Zinc (Zn) is an essential micronutrient for plants, but accumulation of excess Zn causes oxidative stress, even though the element is not redox-active. An oxidative stress signature, consisting of multiple oxidative stress related parameters, is indicative of disturbance of redox homeostasis and signaling, but has not been determined after exposure...
The impact of a season-long exposure to moderately elevated tropospheric O3 concentrations on the canopy growth and photosynthetic capacity of two important Brassica crops, spring oilseed rape and broccoli, was studied during three consecutive growing seasons (2007–2009). Brassica napus L. cv. Ability and Brassica oleracea L. cv. Monaco were expose...
At present, screening of the population at risk for gambiense human African trypanosomiasis (HAT) is based on detection of antibodies against native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. Drawbacks of these native VSGs include culture of infective T.b. gambiense trypanosomes in laboratory rodents, necessary for...
At present, all available diagnostic antibody detection tests for Trypanosoma brucei gambiense human African trypanosomiasis are based on predominant variant surface glycoproteins (VSGs), such as VSG LiTat 1.5. During investigations aiming at replacement of the native VSGs by recombinant proteins or synthetic peptides, the sequence of VSG LiTat 1.5...
In plants, ultraviolet (UV)-B acclimation is a complex, dynamic process that plays an essential role in preventing UV-B damage to targets such as DNA and the photosynthetic machinery. In this study we tested the hypothesis that the phytohormone auxin is a component of the regulatory system that controls both UV-mediated accumulation of flavonoids a...
The impact of elevated tropospheric ozone (O3) on the quality of spring oilseed rape (Brassica napus cv Ability) and broccoli (Brassica oleracea L. cv Italic cv Monaco) was assessed during a three year Open – Top Chamber (OTC) experiment. Current ambient O3 levels were compared to an increase of 20 and 40 ppb during 8 h per day over the entire grow...
The current antibody detection tests for the diagnosis of gambiense human African trypanosomiasis (HAT) are based on native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. These native VSGs are difficult to produce, and contain non-specific epitopes that may cause cross-reactions. We aimed to identify mimotopic peptides...
Tropospheric ozone is an important air pollutant with known detrimental effects for several crops. Ozone effects on seed yield, oil percentage, oil yield and 1000 seed weight were examined for spring oilseed rape (Brassica napus cv. Ability). For broccoli (Brassica oleracea L. cv. Italica cv. Monaco) the effects on fresh marketable weight and total...
The cellular redox state is an important determinant of metal phytotoxicity. In this study we investigated the influence of cadmium (Cd) and copper (Cu) stress on the cellular redox balance in relation to oxidative signalling and damage in Arabidopsis thaliana. Both metals were easily taken up by the roots, but the translocation to the aboveground...
Upon chronic UV treatment pavement cell expansion in Arabidopsis leaves is reduced, implying alterations in symplastic and apoplastic properties of the epidermal cells. In this study, the effect of UV radiation on microtubule patterning is analysed, as microtubules are thought to serve as guiding rails for the cellulose synthase complexes depositin...
Plants have evolved a broad spectrum of mechanisms to ensure survival under changing and suboptimal environmental conditions. Alterations of plant architecture are commonly observed following exposure to abiotic stressors. The mechanisms behind these environmentally controlled morphogenic traits are, however, poorly understood. In this report, the...
Erica andevalensis is an endemic species from SW Iberian Peninsula, always growing in metal-enriched and acid soils. In the present study, a comparison was made between wild E. andevalensis plants collected from the field and cultivated ones exposed to different cadmium levels (0, 0.5, 5 and 50 μM). Wild plants contain higher levels of ascorbic aci...
A Nicotiana tabacum L. SR-1 leaf protoplast system was used to study the effects of dehydroascorbate and glutathione on cellular development.
We found that dehydroascorbate is readily taken up by protoplasts and internally reduced to ascorbate. Concomitantly, cell
division was inhibited and cell expansion stimulated. In this respect, dehydroascorba...
The dipeptidyl peptidases (DPP) 8 and 9 belong to the DPP4 activity and/or structure homologues (DASH). Recently, a DPP9-like protein was purified from bovine testes. The aim of the present study was to prove its identity and to investigate the characteristics of this natural enzyme. We report the identification and N-terminal sequence analysis by...
The physiological effects of Cd and Cu have been highlighted in several studies over the last years. At the cellular level, oxidative stress has been reported as a common mechanism in both stress situations. Nevertheless, because of differences in their redox-related properties, the origin of the stress and regulation of these effects can be very d...
The hepatitis B core (HBc) protein has been used successfully in numerous experiments as a carrier for heterologous peptides. Folding and capsid formation of the chimeric proteins is not always achieved easily. In silico analyses were performed to provide further comprehension of the feasibility for predicting successful capsid formation. In contra...
Quantitative traits, such as size and weight in animals and seed yield in plants, are distributed normally, even within a population of genetically identical individuals. For example, in plants, various factors, such as local soil quality, microclimate, and sowing depth, affect growth differences among individual plants of isogenic populations. Bes...
Our previous screening of a Glossina morsitans morsitans lamdagt11 salivary gland expression library with serum of a tsetse fly exposed rabbit identified a cDNA encoding Tsetse Antigen5 (TAg5, 28.9 kDa), a homologue of Antigen5 sting venom allergens. Recombinant TAg5 was produced in Sf9 cells in order to assess its immunogenic properties in humans....
Exposure of plants to mild chronic stress can cause induction of specific, stress-induced morphogenic responses (SIMRs). These responses are characterized by a blockage of cell division in the main meristematic tissues, an inhibition of elongation and a redirected outgrowth of lateral organs. Key elements in the ontogenesis of this phenotype appear...
Plants are sessile organisms, and consequently cannot avoid exposure to stressful environmental conditions. Exposure to mild stress conditions can induce active acclimation responses, while more severe conditions cause metabolic disruptions. A common plant acclimation response to a variety of environmental stressors is the accumulation of antioxida...
East Coast fever, an acute lymphoproliferative disease of cattle, is caused by the apicomplexan parasite Theileria parva. Protective immunity is mediated by CD8(+) cytotoxic T lymphocytes directed against schizont-infected cells. The polymorphic immunodominant molecule, although an antibody-inducing surface molecule of the schizont, has been hypoth...
The possible involvement of glucose (Glc) carriers in the uptake of vitamin C in plant cells is still a matter of debate. For the first time, it was shown here that plant cells exclusively take up the oxidised dehydroascorbate (DHA) form. DHA uptake is not affected by 6-bromo-6-deoxy-ascorbate, an ascorbate (ASC) analogue, specifically demonstratin...
Chlorogenic acid (CGA) is one of the most abundant phenolic compounds in tomato (Solanum lycopersicum). Hydroxycinnamoyl CoA quinate transferase (HQT) is the key enzyme catalysing CGA biosynthesis in tomato. We have studied the relationship between phenolic accumulation and UV-susceptibility in transgenic tomato plants with altered HQT expression....
The hepatitis B virus core (HBc) virus-like particle (VLP) is known as one of the most immunogenic antigens and carrier vehicles in different immunization strategies. Recent findings are suggesting the potential of the HBc VLPs as an oral immunogen. Here, we focus on the induction of serum humoral responses by oral administration of HBc VLPs in pre...
The balance between antioxidants, such as ascorbate (ASC) and glutathione, and oxidative reactive oxygen species (ROS) is
known to play a pivotal role in the response of plant cells to abiotic stress. Here cell cultures of Arabidopsis thaliana were investigated with regard to their response to elevated levels of cadmium. At concentrations <100 μM,...
The nucleocapsid or core particle of the hepatitis B virus has become one of the favourite recombinant vaccine carriers for foreign peptides, proteins and stimulatory oligonucleotides. The core protein consists of three regions: an N-terminal, a central and a C-terminal region that can accommodate the addition or insertion of the foreign sequences....
Plants exposed to sub-lethal abiotic stress conditions exhibit a broad range of morphogenic responses. Despite the diversity of phenotypes, a generic 'stress-induced morphogenic response' can be recognized that appears to be carefully orchestrated and comprises three components: (a) inhibition of cell elongation, (b) localized stimulation of cell d...
Ultraviolet B (UV-B) acclimation comprises complex and poorly understood changes in plant metabolism. The effects of chronic and ecologically relevant UV-B dose rates on Arabidopsis thaliana were determined. The UV-B acclimation process was studied by measuring radiation effects on morphology, physiology, biochemistry and gene expression. Chronic U...
Xyloglucan endotransglycosylase/hydrolases (XTHs) are enzymes that cleave and rejoin xyloglucan chains. To trace the evolutionary origin of XTHs, we used Selaginella kraussiana, a representative of the most primitive land plants (Lycopodiophyta). A Southern blot with a digoxigenin-labeled probe, designed on the conserved catalytic site of XTHs, ind...
In angiosperms xyloglucan endotransglucosylase (XET)/hydrolase (XTH) is involved in reorganization of the cell wall during growth and development. The location of oligo-xyloglucan transglucosylation activity and the presence of XTH expressed sequence tags (ESTs) in the earliest diverging extant plants, i.e. in bryophytes and algae, down to the Phae...
Copper is a naturally occurring trace metal with toxic properties for man and environment. It is assumed that toxicity is primarily caused by oxidative damage, generated through the production of reactive oxygen species. Copper is, however, also an essential element, which means trace amounts are necessary for biological processes to function prope...
Tocopherols and tocotrienols are present in mature seeds. Yet, little is known about the physiological role and the metabolism of these compounds during seed development. Here we present data on tocopherol and tocotrienol accumulation during seed development in Vitis vinifera L. cv. Albert Lavallée (Royal). This species was chosen for its ability t...
To better understand the response of a plant to O3 stress, an integrated microarray analysis was performed on Arabidopsis plants exposed during 2 days to purified air or 150 nl l−1 O3, 8 h day−1. Agilent Arabidopsis 2 Oligo Microarrays were used of which the reliability was confirmed by quantitative real-time PCR of nine randomly selected genes. We...
Tocopherols and tocotrienols are vitamin E compounds, differing only in the saturation state of the isoprenoid side chain. Tocopherol biosynthesis, physiology and distribution have been studied in detail. Tocopherols have been found in many different plant species, and plant tissues. In contrast, comparatively little is known about the physiology a...
A tissue print followed by a xyloglucan endotransglycosylase assay revealed that XET activity is present at sites of cell
elongation in both roots and shoots of the lycopodiophyte Selaginella kraussiana. This paper provides the first report and analysis of a xyloglucan endotransglycosylase/hydrolase (XTH) cDNA sequence, isolated
from a club moss. I...
Glutathione is generally accepted as the principal electron donor for dehydroascorbate (DHA) reduction. Moreover, both glutathione and DHA affect cell cycle progression in plant cells. But other mechanisms for DHA reduction have been proposed. To investigate the connection between DHA and glutathione, we have evaluated cellular ascorbate and glutat...
Nonlinear regression analysis (NLR) is applied to quantify the dynamic response of non-photochemical fluorescence quenching (NPQ) of Trifolium repens cv. Regal upon dark to light transition. Commonly, only steady-state levels of NPQ are evaluated, ignoring transient kinetics. Experimental NPQ kinetics are fitted best with a sum of two functions: a...
In cell suspension cultures of Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) a rapid and concentration-dependent accumulation of H(2)O(2) is induced by excess concentrations of copper (up to 100 microM). This specific and early response towards copper stress was shown to be extracellular. Addition of 300 U of catalase per ml decreased the level o...
Flavocytochrome c-sulfide dehydrogenase (FCSD), an enzyme that catalyzes the reversible conversion of sulfide to elemental sulfur in vitro, is common to bacteria that utilize reduced sulfur compounds as electron donors in the process of carbon dioxide fixation. FCSD is a heterodimer containing two different cofactors, a flavin (FAD) and one or two...
The napB gene of the pathogenic bacterium Haemophilus influenzae encodes a dihaem cytochrome c, the small subunit of a heterodimeric periplasmic nitrate reductase similar to those found in other bacteria. In order to obtain sufficient protein for biophysical studies, we aimed to overproduce the recombinant dihaem protein in Escherichia coli. Initia...
The amino acid sequence of Ectothiorhodospira vacuolata cytochrome c-552, isolated from membranes with n-butanol, shows that it is a protein of 77 amino acid residues with a molecular mass of 9,041 Da. It is closely related to the cytochrome subunit of Chlorobium limicola f. sp. thiosulfatophilum flavocytochrome c-sulfide dehydrogenase (FCSD), havi...
A soluble cytochrome b(558) from the purple phototropic bacterium Ectothiorhodospira vacuolata was completely sequenced by a combination of automated Edman degradation and mass spectrometry. The protein, with a measured mass of 10,094.7 Da, contains 90 residues and binds a single protoheme. Unexpectedly, the sequence shows homology to eukaryotic cy...
The complete sequence of Bacillus pasteurii cytochrome c-553 was determined by standard methods of Edman degradation of overlapping peptides combined with mass spectrometry. The protein contains 92 residues and a single heme-binding site. It is most similar to Bacillus licheniformis, Bacillus PS3, and Bacillus subtilis cytochromes c-551, which are...
The complete primary structure of an unusual soluble cytochrome c isolated from the obligate methylotrophic bacterium Methylophilus methylotrophus has been determined to contain 124 amino acids and to have an average molecular mass of 14293.0 Da. The sequence has two unusual features: firstly, the location of the heme-binding cysteines is far downs...
Tumor necrosis factor (TNF) is a central mediator of a number of important pathologies such as the systemic inflammatory response syndrome. Administration of high TNF doses induces acute anorexia, metabolic derangement, inflammation, and eventually shock and death. The in vivo effects of TNF are largely mediated by a complex network of TNF-induced...
The genes encoding the mature forms of mouse (mOB) and human OB (hOB) protein (also called leptin) were fused to the secretion signal coding sequence of the Escherichia coli outer membrane protein A (sOMP A). The hybrid genes were preceded by a ribosome binding site (RBS) and were expressed under transcriptional control of both the lipoprotein prom...
We compared three crystal structures of human interleukin 5 (hIL5) expressed in either E. coli (hIL5E.coli), Sf9 cells (hIL5sf9) or Drosophila cells (hIL5Drosophila). The dimeric hIL5 structures show subtle but significant conformational differences which are probably a consequence of the different crystallization conditions trapping this protein i...
The leptin receptor is a class I transmembrane protein with either a short or a long cytoplasmic domain. Using chemical cross-linking we have analyzed the binding of leptin to its receptor. Cross-linking of radiolabeled leptin to different isoforms of the leptin receptor expressed on COS-1 cells reveals leptin receptor monomer, homodimer, and oligo...
Leptin, a fat secreted hormone, regulates ingestive behaviour and energy balance by binding to a specific receptor. Using site-directed mutagenesis, we screened for single amino acid residues in human leptin which are critical for receptor binding and biological activity. Here we report that one of these mutants has in vivo antagonistic properties....
Binding studies were conducted to identify the anatomical location of brain target sites for OB protein, the ob gene product. 125I-labeled recombinant mouse OB protein or alkaline phosphatase-OB fusion proteins were used for in vitro and in vivo binding studies. Coronal brain sections or fresh tissue from lean, obese ob/ob, and obese db/db mice as...
The development of the different lineages of the hematopoietic system is regulated by a set of intercellular interactions, either by direct cellular contact or via the release of soluble factors. Proliferation, self-renewal, and lineage commitment are all strongly influenced by a complex network of external factors. Among these, cytokines play a cr...
The receptor for interleukin-5 (IL-5) is composed of two different subunits. The IL-5 receptor alpha (IL-5R alpha) is required for ligand-specific binding while association with the beta-chain results in increased binding affinity. Murine IL-5 (mIL-5) has similar activity on human and murine cells, whereas human IL-5 (hIL-5) has marginal activity o...
The recent positional cloning of the mouse ob gene and its human homology has provided the basis to investigate the potential
role of the ob gene product in body weight regulation. A biologically active form of recombinant mouse OB protein was overexpressed
and purified to near homogeneity from a bacterial expression system. Peripheral and central...
A characteristic feature of chronic allergic diseases such as asthma is the increase in eosinophil numbers in the inflamed tissue. In light of its specificity for the development of eosinophils, interleukin-5 (IL-5) is considered the most important cytokine involved in the regulation of eosinophilia. Hence, an antagonist for IL-5 activity is a new...
Interleukin (IL)-5 binds to a cell surface receptor composed of two polypeptide chains, alpha and beta, both belonging to the hemopoietic cytokine receptor family. Mouse cells expressing common mouse beta chain (AIC2B) that were transfected with human IL-5 receptor (R)alpha cDNA proliferated in response to picomolar concentrations of human IL-5, in...
A detailed structure-function analysis of human interleukin 5 (hIL5) has been performed. The hIL5 receptor is composed of two different polypeptide chains, the alpha and beta subunits. The alpha subunit alone is sufficient for ligand binding, but association with the beta subunit leads to a 2- to 3-fold increase in binding affinity. The beta chain...
We have performed a detailed structure-function analysis of human interleukin 5 (hIL5) and its receptor. By testing a hIL5 mutant panel in a solid phase binding assay and a proliferation assay using hIL5 dependent cell-lines, areas on hIL5 involved in either the receptor alpha-subunit interaction or in receptor activation were identified. Epitope m...
Using a fusion protein of the human interleukin-5-receptor alpha chain (hIL5R alpha) and the human IgG C gamma 3 chain (hIL5R alpha-h gamma 3), we have developed a solid-phase assay for high-flux screening of a collection of synthetic compounds. We report on the identification of isothiazolone derivatives as potent inhibitors of binding of interleu...
Recombinant human interleukin-5 (hIL-5) has been expressed at high levels and produced in large quantities in baculovirus infected Sf9 insect cells. The glycosylated protein was purified using immuno-affinity chromatography and gel filtration. Purified hIL-5 has been crystallized using standard vapour diffusion techniques with PEG as a coprecipitan...