THIJS, Sofie; Van Dillewijn, Pieter; SILLEN, Wouter; TRUYENS, Sascha; HOLTAPPELS, Michelle; D'HAEN, Jan; CARLEER, Robert; WEYENS, Nele; AMELOOT, Marcel; Ramos, Juan-Luis; VANGRONSVELD, Jaco
Background and aims Numerous microorganisms have been isolated from trinitrotoluene (TNT)-contaminated soils, however TNT tends to persist, indicating that the microbial biomass or activity is insufficient for degradation. Deep-rooting trees at military sites have been found to take-up contaminants from groundwater, and the extensive root and endosphere provide ideal niches for microbial TNT-transformations. Methods We characterised the rhizosphere, root endosphere and endo-phyllosphere bacteria of Acer pseudoplatanus growing at a historically TNT-contaminated location, using 16S rRNA gene fingerprinting, bacteria isolation, oxidoreductase gene-cloning, in planta growth-promotion (PGP) tests, inoculation, plant physiology measurements and microscopy. Results Based on terminal-restriction-fragment-length-polymorphism analysis, bulk soil and...
Vrancken, K.; Valcke, R.; Schoofs, H.; Deckers, T.
When a plant is infected by a pathogen, several defence mechanisms are induced in planta. A rapid production of reactive oxygen species (ROS) released into the apoplast, is one of the earliest responses to pathogen infection. We investigated the possible role of these antioxidants in Pyrus communis 'Conference' after infection with Erwinia amylovora. We analysed expression of the genes for SOD, APX and CAT and their diverse isoforms with Real Time qPCR. Infected and mock infected leaves, but also young and old leaves were included. In this study, we noticed a significant difference in transcription levels of some isoforms between...
Ghesquiere, K.; Vrancken, K.; Valcke, R.; Schoofs, H.; Deckers, T.
Fire blight is a major threat to pear and apple production caused by the gram negative bacterium Erwinia amylovora. Pear trees were treated three times with metal solutions of Mn or Cu starting at the white bud stage. Subsequently, they were artificially infected with E. amylovora. Infection rates were assessed and ooze formation was monitored. At 7 days after infection, an inhibitory effect of Mn on the rate of infection could be seen. In a second trial, pear trees carrying young fruits were treated three times at 10-day intervals with Cu or Mn solutions. Chlorophyll fluorescence imaging analysis carried out...
Chlorophyll fluorescence is a now well-established technique for the analysis of photosynthesis in plants and algae. Fluorescence transients (Kautsky curves), exhibited by photosynthetic organisms under different conditions provide detail information about the structure, conformation and function of the photosynthetic apparatus, especially of photosystem II. The analysis of the so-called OJIP-curve and of the pulsed-amplitude-modulated fluorometry in conjunction with the saturation pulse method has been very successful. In recent years, the versatility of these techniques has increased by the development of imaging systems. High resolution systems make it possible to investigate the photochemical efficiency of individual cells in a leaf or...
VRANCKEN, Kristof; Schoofs, H.; Deckers, T.; Valcke, Roland
Delegido, Jes??s; Van Wittenberghe, Shari; Verrelst, Jochem; Ortiz, Violeta; Veroustraete, Frank; VALCKE, Roland; Samson, Roeland; Rivera, Juan P.; Tenjo, Carolina; Moreno, Jos??
Spatially distributed chlorophyll content of urban vegetation provides an important indicator of a plant's health status, which might depend on the habitat quality of the specific urban environment. Recent advances in optical remote sensing led to improved methodologies to monitor vegetation properties. The hyperspectral index NAOC (Normalized Area Over reflectance Curve) is one of these new tools that can be used for mapping chlorophyll content. In this paper we present the work done to quantify vegetation chlorophyll content over the city of Valencia (Spain) based on chlorophyll measurements of four representative tree species: the London plane tree (Platanus x. acerifolia),...
Zhu, Qiang; Dugardeyn, Jasper; Zhang, Chunyi; M??hlenbock, Per; Eastmond, Peter J.; VALCKE, Roland; De Coninck, Barbara; Oden, Sevgi; Karampelias, Michael; Cammue, Bruno P. A.; Prinsen, Els; Van der Straeten, Dominique
Recently, we reported that the novel mitochondrial RNA editing factor SLO2 is essential for mitochondrial electron transport, and vital for plant growth through regulation of carbon and energy metabolism. Here, we show that mutation in SLO2 causes hypersensitivity to ABA and insensitivity to ethylene, suggesting a link with stress responses. Indeed, slo2 mutants are hypersensitive to salt and osmotic stress during the germination stage, while adult plants show increased drought and salt tolerance. Moreover, slo2 mutants are more susceptible to Botrytis cinerea infection. An increased expression of nuclear-encoded stress-responsive genes, as well as mitochondrial-encoded NAD genes of complex I and...
Van Wittenberghe, Shari; Alonso, Luis; Verrelst, Jochem; HERMANS, Inge; VALCKE, Roland; Veroustraete, Frank; Moreno, Jos??; Samson, Roeland
To better understand the potential uses of vegetation indices based on the sun-induced upward and downward chlorophyll fluorescence at leaf and at canopy scales, a field study was carried out in the city of Valencia (Spain). Fluorescence yield (FY) indices were derived for trees at different traffic intensity locations and at three canopy heights. This allowed investigating within-tree and between-tree variations of FY indices for four tree species. Several FY indices showed a significant (p b 0.05) and important effect of tree location for the species Morus alba (white mulberry) and Phoenix canariensis (Canary Island date palm). The upward FY...
VRANCKEN, Kristof; HOLTAPPELS, Michelle; Schoofs, Johan; Deckers, T.; Treutter, D.; VALCKE, Roland
Flavonoids, which are synthesized by the phenylpropanoid-flavonoid pathway, not only contribute to fruit colour and photoprotection, they also may provide antimicrobial and structural components during interaction with micro-organisms. A possible response of this pathway was assessed in both mature and immature leaves of shoots of 2-year-old pear trees cv. Conference, which were inoculated with the gram-negative bacterium Erwinia amylovora strain SGB 225/12, were mock-inoculated or were left untreated. The phenylpropanoid flavonoid pathway was analysed by histological studies, by gene expression using RT-qPCR and by HPLC analyses of the metabolites at different time intervals after infection. Transcription patterns of two key...
Van Goethem, Davina; De Smedt, Sebastiaan; VALCKE, Roland; Potters, Geert; Samson, Roeland
In recent years, temperate bamboo species have been introduced in Europe not only as an ornamental plant, but also as a new biomass crop. To measure adaptation stress of bamboo to the climate of Western Europe, chlorophyll fluorescence was measured on a diurnal and seasonal basis in Ballyboughal, Co. Dublin, Ireland. Measurements were attained on the leaves of each node of Phyllostachys humilis. The most frequently used parameter in chlorophyll fluorescence is the photosynthetic efficiency (Fv/Fm). A seasonal dip - as well as a larger variation - of Fv/Fm in spring compared to the rest of the year was observed....
Vrancken, K; Holtappels, M; Schoofs, H; Deckers, T; Treutter, D; Valcke, R
Flavonoids, which are synthesized by the phenylpropanoid???flavonoid pathway, not only contribute to fruit colour and photoprotection, they also may provide antimicrobial and structural components during interaction with micro-organisms. A possible response of this pathway was assessed in both mature and immature leaves of shoots of 2-year-old pear trees cv. Conf??rence, which were inoculated with the gram-negative bacterium Erwinia amylovora strain SGB 225/12, were mock-inoculated or were left untreated. The phenylpropanoid???flavonoid pathway was analysed by histological studies, by gene expression using RT-qPCR and by HPLC analyses of the metabolites at different time intervals after infection.
Transcription patterns of two key genes anthocyanidin...
Vrancken, K.; Holtappels, M.; Schoofs, H.; Deckers, T.; Valcke, R.
Plants are host to a large amount of pathogenic bacteria. Fire blight, caused by the bacterium Erwinia amylovora, is an important disease in Rosaceae. Pathogenicity of E. amylovora is greatly influenced by the production of exopolysaccharides, such as amylovoran, and the use of the type III secretion system, which enables bacteria to penetrate host tissue and cause disease. When infection takes place, plants have to rely on the ability of each cell to recognize the pathogen and the signals emanating from the infection site in order to generate several defence mechanisms. These mechanisms consist of physical barriers and the production...
Spoustova, P.; Synkova, H.; Valcke, R.; Cerovska, N.
The effect of Potato virus Y (NTN) (PVY) infection upon photosynthesis was analysed in transgenic Pssu-ipt tobacco overproducing endogenous cytokinins in comparison with control, nontransgenic Nicotiana tabacum plants. The course of the infection from the early to the late stage was monitored by measuring of photosynthetic gas exchange and fast chlorophyll (Chl) a fluorescence induction kinetics. Leaf photosynthesis was also analysed using Chl fluorescence imaging (Chl-FI). From the different fluorescence parameters obtained using Chl-FI, the nonphotochemical quenching (NPQ) proved to be the most useful parameter to assess the effect of PVY infection. On the other hand, Chl-FI was found to...
Van Wittenberghe, Shari; Alonso, Luis; Verrelst, Jochem; Hermans, Inge; Delegido, Jesus; Veroustraete, Frank; Valcke, Roland; Moreno, Jose; Samson, Roeland
Passive steady-state chlorophyll fluorescence (Fs) provides a direct diagnosis of the functional status of vegetation photosynthesis. With the prospect of mapping Fs using remote sensing techniques, field measurements are mandatory to understand to which extent Fs allows detecting plant stress in different environments. Trees of four common species in Valencia were classified in either a low or a high local traffic exposure class based on their leaf magnetic value. Upward and downward hyperspectral fluorescence yield (FY) and indices based on the two Fs peaks (at 687 and 741 nm) were calculated. FY indices of P. canariensis and P. x acerifolia...
Guedens, Wanda; Reynders, Monique; Asperges, Michel; Reygel, Patrick
Vrancken, K.; Schoofs, H.; Deckers, T.; Valcke, R.
Hydrogen peroxide plays a critical role in the
expression of disease resistance in several plant/pathogen
interactions. It serves as a substrate for oxidative crosslinking
of various plant cell wall components leading to the
reinforcement of the cell structure, as a direct toxin against
the pathogen and as a signal molecule for the induction of
defence-related genes in the adjacent, still healthy tissues.
In plant cells, enzymes and redox metabolites act in synergy
to carry out the detoxification of hydrogen peroxide
and other reactive oxygen species (ROS). Superoxide dismutase
(SOD) catalyses the dismutation of superoxide to
hydrogen peroxide, catalase (CAT) dismutates hydrogen
peroxide to oxygen and water, and ascorbate peroxidase
(APX) reduces hydrogen peroxide...
Cortleven, Anne; Valcke, Roland
Cytokinin is known to be involved in many processes related to plastid
development and function but the exact role of cytokinin in photosynthesis
remains elusive. To investigate more profoundly the effects of cytokinin in
this process, the photosynthetic activity of transgenic Pssu-ipt and 35S:CKX1
tobacco (Nicotiana tabacum) plants with respectively elevated and reduced
endogenous cytokinin content was evaluated. Pigment analysis indicated
that elevated endogenous cytokinin content resulted in increased pigment
content. Functional analysis of the photosynthetic apparatus by chlorophyll
a fluorescence and in vitro electron transport measurements clearly showed
that changing the endogenous cytokinin content affects the activity of
the photosynthetic apparatus. Surprisingly, both an increase as well as a
Reygel, Patrick; Asperges, Michel; Guedens, Wanda
Deze bijdrage bevat materiaal voor de organisatie van een uitgebreid seminarie in het domein van de vakdidactiek van de Biologie/Natuurwetenschappen. De beschreven workshop en alle experimenten werden in de loop van meerdere jaren getest en gebruikt in een academische lerarenopleiding in het kader van het opleidingsonderdeel Vakdidactiek Biologie/Chemie aan de UHasselt. Het seminarie of een selectie ervan kan ook gebruikt worden in professionele bacheloropleidingen en mits tekstaanpassingen in het Secundair Onderwijs en dit zowel binnen het meeruren pakket Biologie als Natuurwetenschappen.
WEYENS, Nele; SCHELLINGEN, Kerim; DUPAE, Joke; CROES, Sarah; VAN DER LELIE, Daniel; VANGRONSVELD, Jaco
Phyoremediation has been proposed as an economically interesting alternative for remediation of metal contaminated soils. It can be applied on extended and diffusely contaminated areas and targets the "bioavailable" fraction of metals, which is the most relevant fraction from an environmental risk assessment perspective. The most important drawback is the long time period required for remediation process. Main limiting factors for an efficient phytoextraction are plant availability of metals, metal uptake and phytotoxicity. These constraints can be conquered by (1) choosing plant cultivars with both high metal uptake capacity and high biomass production; by (2) increasing metal availability and uptake...
Buekers, J.; STEEN REDEKER, Erik; Smolders, E.
Generic risk assessments of lead (Pb) toxicity to wildlife puts soil Pb limits below the natural background. The Tissue Residue Approach (TRA) is an alternative method by which the current risk of Pb to wildlife can be assessed and avoids uncertainties about Pb exposure routes or bioavailability of environmental Pb. About 80 toxicity studies were reviewed of which 19 experimental and 6 field studies with mammals and birds were selected. Blood lead concentration (Pb-B, mu g Pb/dL) was used as the index of exposure. The highest No Observed Effect Concentrations (NOECs) varied about 1600-fold among species and tests when expressed...