Research team

Integrated Molecular Plant Physiology Research (IMPRES)

Expertise

My expertise lies in the analysis of redox metabolism and oxidative stress processes, with particular emphasis on plant responses to abiotic stress factors (e.g. temperature, water deficit). We quantitatively analyze multiple oxidative stress components, including, cell level damage (e.g. protein oxidation, lipid peroxidation, membrane leakage), proteins and enzymes (e.g. antioxidant enzymes, glutaredoxin, thioredoxin) and redox metabolites (e.g., ascorbate, H2O2, glutathione). In addition, we analyze plant metabolic responses that are pertinent to stress responses, such as photorespiration, proline metabolism, C-fixation, TCA cycle and primary metabolism. Analyses are standardized and optimized on model plant species, i.e. Zea mays and Arabidopsis thaliana, but tissues from multiple other species, plants and animals, have also been analyzed. Samples are processed in a semi high-throughput protocol, allowing the simultaneous analysis of relatively large numbers of samples. All analyses include assistance in data processing (calculations) and interpretations.

Unraveling winter sleep to understand spring reactivation: improved understanding of leaf out phenology in temperate deciduous trees by gaining insight in environmental controls of bud dormancy. 01/01/2019 - 31/12/2022

Abstract

By affecting the uptake of carbon and the transpiration of water by forests, tree phenology also influences local weather and long-term climate change. Studying spring phenology of temperate trees is thus more than just a biologist's hobby. Despite a wealth of observations of the date that leaves appear in spring, this process is still not fully understood. Leaf out can occur at very different moments in spring, despite similar spring weather. Part of the reason is that spring leaf out is only the end point of an entire winter of bud responses to cold temperatures, to warm temperatures, and to changes in day length. To fully understand the climatic controls over spring phenology, and thus to be able to produce models that can accurately predict future changes in spring phenology, insight is needed into what happens during the long winter, when buds are apparently asleep. This project focuses on just that: what happens during the bud's resting phase that makes them more or less responsive to warmer spring temperatures. We will conduct two large experiments in which temperature and day length will be altered, and throughout the entire winter season monitor changes in gene expression, in metabolite concentrations, and in depth of dormancy. The ultimate aim is to advance insight in spring phenology, but also to identify genes or metabolites that could give information on the state of dormancy during winter, and thereby on the bud's sensitivity to spring warming. -

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Shifting rainfall regimes: a multi-scale analysis of ecosystem response (REGIME SHIFT). 01/01/2019 - 31/12/2022

Abstract

Recent climate change research reveals a novel and significant trend: weather patterns at mid-latitudes, such as in temperate western Europe, are getting more persistent. With respect to rainfall, this means longer droughts, but also longer periods with excessive rain. No comprehensive study has hitherto investigated the ecological consequences of such regime shifts. Can ecosystems adapt, or will the alternation between drought stress and soil water saturation exhaust them? Will this select for communities with novel trait combinations and more volatile species dynamics? And will these novel systems still be robust in the face of further changes in the environment? This study explores the potential impact of the ongoing shift in the frequency of dry/wet cycles at multiple, connected levels of biological organization. It does so in a new, large-scale set-up at UAntwerp built in the framework of the developing European infrastructure for ecosystem research 'AnaEE'. The design simulates changes in rainfall and associated temperature changes in the open air, using a gradient with eight precipitation regimes so that non-linearity and tipping points can be discerned with great precision. The project scope ranges from plants to soil biota such as bacteria and fungi, and from metabolism and genetic regulation assessed with bioinformatics to ecosystem processes. This multi-scale approach explicitly acknowledges the interwoven nature of ecosystems, with knowledge of molecular and cellular changes being instrumental to mechanistically explain the whole-system-scale effects on productivity, greenhouse gas fluxes and biodiversity dynamics. Different experiments are planned each year: (i) year 1 features a gradient in alternating dry/wet cycles, from 1 to 60 days, across a full growing season; (ii) year 2 focuses on legacy effects and the importance of changes of soil communities; (iii) year 3 matches precipitation regimes to corresponding temperature regimes to study the impact of drought-associated warming (an important natural feedback that can greatly increase plant stress). A series of connected, hypothesis-driven measurements is carried out, which will be integrated using structural equation modelling (path analysis) and ecosystem modelling. The project team has successfully collaborated in the past, and the complementary expertise brought together here should yield both significantly increased understanding of key processes as well as new avenues to climate change impact mitigation.

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Aluminum toxicity in plants, understanding responses to aluminum in sensitive and tolerant rye genotypes 15/07/2017 - 14/07/2018

Abstract

Aluminum (Al) is an important toxic heavy metal, considerable reducing plant growth and crop production, in particular in acidic soils, worldwide. Rye (Secale cereale), is a crop particularly known for its tolerance to acidic soils, and to Al. Therefore, understanding the Al-tolerance mechanism, at the molecular, mechanistic level, will provide a basis for tolerance-improvement, also for other crops. Previously (3 years PhD work by the candidate), two rye genotypes were used, Beira and RioDeva, respectively more tolerant and more sensitive to Al, to unravel the underlying molecular mechanisms. Young rye plants were exposed to sub-lethal doses of Al, for short periods of time (24, 48h), and analyzed at multiple organizational levels. Analyses included photosynthesis, antioxidant metabolism, and several other defense responses. The analysis demonstrates that there are differences at the molecular level, between the genotypes, and differences in response to Al, at the level of defense responses. This work has been performed by the candidate at the University of Porto in collaboration with the IMPRES group at the University of Antwerp. The aim of the DocPro-project, is to deepen the understanding of Al-tolerance in rye, by expanding on the results obtained so far, with expertise at the University of Antwerp (IMPRES laboratory, prof. H. Asard & prof. G. Beemster). The specific objectives of this project are 1) the identification of the cellular basis of the growth response in the leaf growth zone (i.e. meristematic zone and elongation zone), through kinematic growth analysis. This identification will be used to analyze, zone-specific, biochemical and molecular responses to Al. And 2), a genome-wide transcriptome-level analysis (through Next Generation Sequencing) of the Al-response in each genotype. This will result in identification of molecular responses to Al that mediate the whole organ growth response, and which will be of interest for future basic and applied research. The overall work on Al toxicity by the candidate, is novel in that it focusses on acute Al toxicity in rye seedlings, and applies genotype-comparison to unravel tolerance mechanisms. Two elements contribute to guaranteeing the successful outcome of this project, i.e. 1) the work performed so far (in Portugal) will result in 3 publications (A1), and, by itself, could be sufficient to obtain a PhD at the home institution. 2) the expertise of the IMPRES laboratory, fits seamless to the previous work of the candidate, and is a natural extension that will result in a joint PhD and an additional high-impact publication.

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MOMEVIP - Molecular and metabolic bases of volatile isoprenoid-induced resistance to stresses. 01/01/2011 - 31/12/2013

Abstract

The MOMEVIP partners will integrate competences in ecology, physiology, biochemistry, molecular biology, functional genomics and bioinformatics to improve knowledge about the molecular and metabolic bases of VIP biosynthesis, and the functions of VIP (isoprene, monoterpenes and sesquiterpenes, collectively) in plant protection, per se and when interacting with other defensive pathways.

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THERMOTOL-Are plants raised in a warm, high-CO² world more tolerant to temperature extremes? 01/01/2008 - 31/12/2011

Abstract

Global temperatures and atmospheric CO² concentrations are expected to increase, and so is the frequency and intensity of climate extremes. The main aim of this project is therefore to test whether plants raised under warmer conditions and/or elevated atmospheric CO² concentrations are more tolerant to current and future heat stress than plants grown under current conditions. For this, we will grow wild-type Arabidopsis thaliana (Heynh.) plants throughout their entire life cycle under either current climate conditions or a variety of future climate scenarios, and expose these plants to one or several, two-day heat pulses of different intensity.

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Changes in the stress sensitivity of plants and ecosystems under climate change conditions. 01/07/2007 - 30/06/2011

Abstract

The central research question of this project is whether the resistance of species-rich plant communities to different stress factors will change in a future climate. To this end we will grow grassland mesocosms in sunlit controlled chambers under either the present or future climate conditions, and expose them to a wide range of stressors: tropospheric ozone, drought, nitrogen deficiency, nitrogen saturation (eutrophication), and heavy metals (cadmium). Stressors will be applied separately to assess dose-response relations, but also in combination to examine their interactive impact. By combining expertise from ecology, plant physiology, and biochemistry, we will evaluate the responses to stress in a future climate across a wide range of biological complexity, from cell to ecosystem.

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Project website

Characterization of structure-function relations in cytochromes b561, new players in vitamin C metabolism of plants and animals. 01/02/2007 - 31/07/2007

Abstract

Despite the essential role of vitamin C in the protection of plants and animals against threatening environmental conditions, important aspects of vitamin C metabolism remain unknown. This project aims at the characterization of a poorly characterized group of proteins that play a role in vitamin C maintenance and in oxidative stress defense responses.

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Ascorbate metabolism in plants: physiological function and biochemical characterization of cytochromes b561 01/01/2007 - 31/12/2010

Abstract

The long term goal of the research is the understanding of ascorbate metabolism in plants and animals. More specifically, this project investigates the physiological function and mechanism of action of cytochromes b551 (Cyts b561). These are widespread intrinsic membrane proteins, using ascorbate as an electron donor for trans-membrane electron transport (Okuyama et al. 1998). Cyts b561 play a yet unidentified role in ascorbate metabolism. Recent indications suggest that Cyts b561 may provide a link between iron and ascorbate metabolism, at least in mice (Mckie et at. 2001). The homology between mouse and Arabidopsis Cyts b561 is considerable, suggesting a similar function in plants. Arabidopsis is proposed as a model plant for these studies.

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A new link between iron and vitamin C metabolism: the role of cytochromes b561. 01/05/2005 - 31/12/2006

Abstract

Vitamin C (ascorbate) plays an essential role in numerous physiological processes in animals and plants. In this project, role of a newly described class of ubiquitous membrane proteins, cytochromes b561, in ascorbate and iron metabolism is investigated. Arabidopsis thaliana is used as a model organism. Results will contribute to our understanding of iron and ascorbate metabolism in plants and mammals.

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Molecular biological characterisation and physiological function of a plant plasma membrane b-type cytochrome. 01/10/2001 - 30/09/2003

Abstract

A plasma membrane b-type cytochrome (cyt b561) is likely to play an essential role in the physiology of higher plant cells. This protein and its function will be studied using a molecular biological approach, including altered expression levels, promotor analysis, in situ hybridisation, and others

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    Influence of ascorbate and dehydroascorbate on the cell cycle regulation in higher plants. 01/10/2001 - 31/12/2002

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      Development of a calory-poor alternative sweetner from plants, for the replacement of glucose in food. 01/05/2001 - 30/09/2001

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        Analysis of the role of the apoplastic antioxidative capacity in the resistance of clover (Trifolium repens L. cv. Regal) to ozone. 01/01/2001 - 31/12/2002

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          Characterization and physiological function of higher plant plasma membrane redox components. 01/10/2000 - 30/09/2005

          Abstract

          Plasma membranes of higher plants contain specific electron transporting redox components, including a specific b-type cytochrome. The physiological function of these components is being investigated by altering their expression levels in Arabidopsis and by investigating their specific distribution in different tissues. The cytochrome will be purified and its primary structure will be analyzed.

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          Ascorbate mediated control of cell cycle and redox state in plant cells. 01/10/2000 - 30/09/2002

          Abstract

          Due to its antioxidant properties, ascorbate (Asc) has a crucial function in the plant cell defence agains oxidative processes. Asc and its oxidised counterpart dehydroascorbate (DHA) are shown to be involved in the regulation of cell division and cell elongation. The ratio between Asc and DHA might be a link of great importance between these phenomena. The nature of this link, and the effect the Asc redox state might have on the plant cell physiology, is the subject of this research.

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            Molecular biological characterisation and physiological function of a higher plant plasma membrane b-type cytochrome. 01/10/2000 - 31/12/2001

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              Set up of subtractive hybridisation as a tool for the identification of specific genes induced under abiotic stress conditions in higher plants. 01/07/2000 - 30/11/2001

              Abstract

              Despite the fact that plants have conserved mechanisms as a response to various stress conditions, however, many specific pathways precluding these conserved mechanisms are mediated by specific stresses. Subtractive hybridisation will be used to identify specific genes activated under stresses induced by heavy metals and UV irradation.

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                Influence of ascorbate on division of Nicotiana tabacum cells 01/01/2000 - 31/12/2001

                Abstract

                Recent research pointed to the possibility of a regulatory action of Asc in the division of plan cells. Together with the Asc concentration, the ratio reduced to oxidised Asc would be of particular importance in this process. The main goal of this project is therefore to try to alter the Asc/DHA ratio by changing the plant cells environment and at the same time follow the effect of these changes on cell division.

                Researcher(s)

                • Promotor: Horemans Nele
                • Co-promotor: Asard Han

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                  Homologous and heterologous expression of an Arabidopsis thaliana plasma membrane cytochrome b. 01/01/2000 - 31/12/2001

                  Abstract

                  Higher plant plasma membranes contain a specific b-type cytochrome (cyt b561) involved in the transmembrane electron transport mediated by the antioxidant ascorbic acid (vitamin C). The physiological function and structural properties of this protein will be investigated through 1) heterologues expression of the Arabidopsis gene in tobacco cell cultures and 2) after transformation of Arabisopsos thaliana with sense and anti-sense constructs.

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                    01/01/2000 - 31/12/2000

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                      Abiotic stress induced responses in redox defence mechanisms and C/N metabolism in plants. 20/12/1999 - 20/12/2002

                      Abstract

                      This project aims at the characterization of plant responses to environmental abiotic stresses, including salinity, osmotic shock, heavy metals and oxidative stress. Special emphasis will be given to antioxidative enzymes, plasma membrane proteins, and the production of active oxygen species. In addition changes in the N metabolism and in photorespiration will be investigated.

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                        01/12/1999 - 31/12/2000

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                          Molecular biological characterisation and physiological function of a plant plasma membrane b-type cytochrome. 01/10/1999 - 30/09/2001

                          Abstract

                          A plasma membrane b-type cytochrome (cyt b561) is likely to play an essential role in the physiology of higher plant cells. This protein and its function will be studied using a molecular biological approach, including altered expression levels, promotor analysis, in situ hybridisation, and others

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                            RAFO financing of an autoclave, essential equipment to the research groups 'Plant Physiology' and 'Ecophysiology and Biochemistry' 01/05/1999 - 31/12/1999

                            Abstract

                            The presence of an operational and reliable autoclave is essential to support the execution of a number of ongoing research projects. The existing equipment was no longer in agreement with the safety regulations and had to be replaced.

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                              Molecular biological characterisation and physiological function of a plant plasma membrane b-type cytochrome. 01/01/1999 - 31/12/2000

                              Abstract

                              A plasma membrane b-type cytochrome (cyt b561) is likely to play an essential role in the physiology of higher plant cells. This protein and its function will be studied using a molecular biological approach, including altered expression levels, promotor analysis, in situ hybridisation, and others

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                                Analysis of the antioxidative mechanisms in Nicotiana tabacum cell culture under biotic and abiotic stress. 01/01/1999 - 30/09/1999

                                Abstract

                                As a defense response to several stress conditions, plants generate a so called oxidative burst, i.e. the rapid production of active oxygen species. However, in order to prevent damage to subcellular macromolecules plants posses a series of antioxidative enzymes. The current project aims at the identification of the antioxidative defense reactions induced in TBY-2 cell cultures.

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                                  The regulation of vitamin C (ascorbic acid) metabolism in plants and the involvement of ascorbic acids as a modulator of cell growth and differentiation. 21/12/1998 - 21/12/2001

                                  Abstract

                                  The aim of this project is to resolve two longstanding, fundamental questions associated with plant vitramin C (ascorbic acid) metabolism namely: 1) the pathway of ascorbic acid biosynthesis and catabolism in plants, including identification of the factors effecting the uptake, accumulation and turnover of this vitamin, 2) the role of ascorbic acid in regulating plant cell growth and differentiation through it's influence on the cell cycle. The knowledge generated from the collaboration between the specialist activities of the participating partners, will expectedly indicate how to manipulate, and to stably increase itracellular ascorbic acid levels in commercially important food crops, leading not only to improved nutritional benefits, but also to novel plants displaying increased resistance to environmental stresses and pollutants.

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                                    Implementation of molecular biology techniques in the laboratory of plant physiology. 01/11/1998 - 30/11/1999

                                    Abstract

                                    The implementation and development of a molecular biological approach has become necessary in several running research projects. The techniques will be applied in the study of plant stress responses and in the characterisation of a plant specific plasma membrane associated protein.

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                                      Ascorbate mediated control of cell cycle and redox state in plant cells. 01/10/1998 - 30/09/2000

                                      Abstract

                                      Due to its antioxidant properties, ascorbate (Asc) has a crucial function in the plant cell defence agains oxidative processes. Asc and its oxidised counterpart dehydroascorbate (DHA) are shown to be involved in the regulation of cell division and cell elongation. The ratio between Asc and DHA might be a link of great importance between these phenomena. The nature of this link, and the effect the Asc redox state might have on the plant cell physiology, is the subject of this research.

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                                        Stress in higher plants: induction of reactive oxygen species and responses to different stress factors 01/12/1997 - 31/12/2001

                                        Abstract

                                        The project is intended to investigate the generation of active oxygen molecules (e.g. oxygen free radicals and hydrogenperoxide) in plants and cell cultures under biotic (pathogens) and abiotic (physical environment) stress conditions. Attempts will be made for the use of Electron Paramagnetic Resonance detection of the radicals.

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                                        • Promotor: Asard Han
                                        • Co-promotor: Clijsters Herman

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                                          Isolation and characterisation of higher plant plasma membrane proteins 01/10/1997 - 31/12/1998

                                          Abstract

                                          The plasma membrane from higher plants contains a series of proteins involved in specific cellular functions including signal perception and transport. Several of these proteins will be purified by column chromatography and characterized at the molecular and enzymatic level.

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                                          • Promotor: Asard Han
                                          • Co-promotor: Van Gestelen Peter

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                                            01/01/1997 - 31/12/1997

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                                              Biochemical and physiological analysis of oxydative stress in higher plants. 01/11/1996 - 31/10/1998

                                              Abstract

                                              Abstract: Similar to other organisms, higher plants are subject to stress as the result of extreme physical conditions or as the result of infections by pathogenic organisms. In the current project biochemical and physiological analyses will be conducted with respect to components (enzymes, active oxygen species, antioxidants) of a variety of defense responses. These studies will be performed at three different levels, i.e. at the tissue, cellular and subcellular levels, in order to obtain an integrated understanding of these responses.

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                                                Detection of oxygen radical generation in plant cell-suspension cultures. 01/05/1996 - 30/04/1998

                                                Abstract

                                                In several cellular defense mechanisms in plants oxygen radicals play an important role. The use of cell-suspension cultures of plants offers important advantages for the study of the mechanisms behind the generation of these components and for the study of other physiological phenomena. The project aims at the installation of such cultures and the primary characterization of the oxygen radical generation.

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                                                  Characterisation of ascorbic acid metabolism and oxygen radical generation at the higher plant plasma membrane. 01/01/1996 - 31/12/1996

                                                  Abstract

                                                  Within intracellular metabolic reactions often originate inevitable by-products which sometimes can be a serious threat to the integrity of the cell. This project focuses on the physiological role of ascorbic acid as antioxidant and the generation of oxygen radicals at the plasma membrane.

                                                  Researcher(s)

                                                  • Promotor: Asard Han
                                                  • Co-promotor: Horemans Nele

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                                                    Characterization and physiological function of higher plant plasma membrane redox components. 01/10/1995 - 30/09/2000

                                                    Abstract

                                                    Plasma membranes of higher plants contain specific electron transporting redox components, including a specific b-type cytochrome. The physiological function of these components is being investigated by altering their expression levels in Arabidopsis and by investigating their specific distribution in different tissues. The cytochrome will be purified and its primary structure will be analyzed.

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                                                      01/05/1995 - 30/04/1997

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                                                        01/01/1995 - 30/09/1995

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                                                          Characterisation and physiological role of a higher plant plasma membrane b-type cytochrome. 01/10/1993 - 30/09/1994

                                                          Abstract

                                                          Redox reactions at the plant plasma membrane are implicated in growth regulation, stress physiology and membrane transport processes. The general aim of this project is the functional and biochemical characterization of redox components involved.

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                                                            01/10/1993 - 30/09/1994

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                                                              01/10/1992 - 30/09/1993

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