My research interest lies in plant growth and metabolism. Understanding plant growth is crucial to improve growth and yield, and becomes increasingly important in a globally changing climate (mainly drought, temperature, elevated CO2). Through analysis at multiple organizational levels (e.g. RNA, antioxidant, metabolite, cell, plant), we contributed to understanding the molecular mechanisms underlying the stress-reducing effect of elevated CO2. Plant Growth analysis: Investigating the growth of the plant from the whole plant down to the cellular level using classic growth analysis and kinematic approaches. Transcript Profiling: Genome wide transcriptional changes focusing on plant (e.g., maize, rice and rye) growth zones. Biochemical profiling: We quantitatively analyze redox metabolites (e.g., ascorbate and glutathione cycle), proteins and enzymes (e.g. antioxidant enzymes, glutaredoxin, thioredoxin), oxidative stress components (e.g. protein oxidation, lipid peroxidation, membrane leakage). 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.
Cold Response Dynamics in the Maize Leaf Growth Zone.
AbstractEarly spring cold is a major limiting factor for maize cultivation in North-Western Europe. Typically, cold spells are only transient and it is known that the capacity of varieties to recover strongly determines their final yield. Nevertheless, in contrast to the direct response to adverse conditions, the mechanisms involved in the recovery of growth have scarcely been studied. This project addresses this critical lack in our knowledge, using an innovative experimental setup where transient exposures to cold are applied at different stages of the development of the 4th leaf of maize lines with contrasting cold tolerance. Advanced phenotyping will be used to quantify the effect on the elongation growth of the leaf, during the cold and upon recovery until the leaf stops growing. Kinematic analysis will be used to quantify the cellular basis of the growth response and recovery. We will determine the molecular changes in the leaf growth zone during the response and recovery phase by means of mRNA sequencing, antioxidant and carbohydrate metabolites analysis and biochemical assays. At the physiological level we will determine the response of photosynthesis and water-relations. Based on this comprehensive and integrated analysis, candidate recovery genes will be identified and mutant and transgenic lines with altered expression of these genes will be acquired and studied in our experimental setup and under field conditions. The obtained knowledge will be scientifically innovative and relevant for plant breeding.
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.
AbstractBy 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. -
- Promotor: Janssens Ivan
- Co-promotor: Abd Elgawad Hamada
- Co-promotor: Asard Han
- Co-promotor: Campioli Matteo
The role of cell wall mechanic properties in the response of maize leaf growth to drought stress.
AbstractDrought is the most limiting factor for crop yield and ecosystem productivity and is predicted to become more prevalent in light of global climate change. One of the first responses of the plant to drought is an inhibition of leaf growth. This is the result of an inhibition of the growth of cells in the growth zone of the leaves. The growth of cells is a driven by a hydrostatic pressure (turgor) generated inside the cells, but is largely controlled by varying the reversible (plastic) and irreversible (elastic) extensibility of the wall. This project aims to further our understanding of the regulation of this crucial process. To this end, we developed a new assay where we measure the extension dynamics in different parts of the growth zone of control and drought stressed leaves after increasing the turgor. Additionally, we determine turgor in unperturbed segments using Psychometry. The extensibility measurements will be validated by independent methods: Atomic Force Microscopy to determine turgor and cell wall elasticity and extensiometry to determine cell wall plasticity. The assays use live tissues in a watery solution. Therefore, we can add putative regulatory substances, H2O2, Abscisic acid, sugars and change the pH to test their effect. These substances are of interest as we have shown that their levels in the growth zone are strongly affected by drought and they have been linked in the literature with the regulation of cell expansion. This project will yield a clear insight in the mechanistic basis of the drought response and its regulation, providing a basis to develop more tolerant crop varieties.
- Promotor: Abd Elgawad Hamada