Metabolism is the set of life-sustaining chemical transformations within the plant cell. On one hand, primary metabolism comprises all metabolic pathways that are essential to the plant's survival, generating compounds (metabolites) that are directly involved in the growth and development of the organism. On the other hand, secondary metabolism produces a large number of specialized compounds that are not essential to the functioning of the plant but are required for the plant to survive in its environment. Secondary plant metabolites are useful in the long term, often for defence purposes, they give plants characteristics such as colour, are also used in communication, signalling and regulation of primary metabolic pathways (e.g. phytohormones).

Plant metabolism

Plant metabolism

 Our research addresses several aspects of the metabolism of plants, in particular the response to altered environmental conditions (such as abiotic/biotic stress, nutrient starvation), using a wide range of techniques from molecular biology, next generation sequencing, biochemistry, phenotyping techniques to MS analytics.


Control of leaf growth dynamics

Dicotyledonous leaves grow with a reoccurring diel growth pattern, which is controlled by endogenous factors like the circadian clock or primary metabolism, but also affected by the leaves environment (e.g. stresses). Photosynthesis is the first step in converting light energy to biomass in the light but plants also grow at night in darkness. For this, biochemical energy is stored in form of starch and carbohydrates. This requires an accurate coordination of growth and plant primary metabolism which also involves the inner clock. Mechanisms stabilizing or adjusting diel leaf growth intensities in changing environment (e.g. changes in nocturnal temperature) will be investigated also in plants lacking or being defective in the endogenous growth control. Unraveling such mechanisms and identification of genes involved in the diurnal control of growth will help to improve and stabilize biomass production in changing and adverse environments.

Leaf growth is quantified for single leaves with high temporal resolution of elongation and expansion and subsequently for whole shoots growth and morphology changes on medium time scale of days taking advantage of the phenotyping tools at IBG-2 (Juelich Plant Phenotyping Centre - JPPC).


Profiling of nitrogen and phosphorus deficiency response in Solanum lycopersicum

Nitrogen (N) and phosphorus (P) are essential macronutrients for plant growth and development. N is an important component of primary and secondary organic compounds. In form of nitrate N plays an important role as a nutrient and signal metabolite. P is also an important mineral nutrient, limiting plant growth. P is a major structural component of nucleic acids and membrane lipids. Furthermore in form of ATP it provides reversible energy storage and regarding signal compounds, like phosphatidylinositol and MAP kinases, P has an important signal function.

Especially for crop plants like tomatoes the availability of these nutrient elements is a major limiting factor for the crop yield, which has an great impact of the economically profit. Hence, the high requirement of N and P fertilizer in the agricultural industry became one of the major costs in crop production. Furthermore P derived from phosphate rock, which is a depleting non-renewable resource and will be exhausted in 60 – 90 years. Therefore finding strategies to reduce the application of N and P fertilizer by improving the N and P use efficiency of crop plants, while maintaining the productivity, is an economically important challenge. A more complete understanding of the metabolism and signaling pathways in N- and P- deficient plants could help investigating new strategies for accomplishing these goals

Therefore the response of hydroponically-grown tomato plants during N and P deficiency will be studied by a large scale profiling of the transcriptome, metabolome and proteome in tomato leaves and fruits. Finally the information will be analyzed and may uncover novel aspects of the mechanism of the metabolism and signaling pathway in tomato plants.


The role of T6P in plant signalling in response to abiotic stress

The aim of this project is to identify the role of trehalose 6-phosphate in Arabidopsis thaliana in the response to abiotic stress, such as cellulose biosynthesis inhibition (CBI) caused by the herbicide isoxaben. It has been shown that the treatment of Arabidopsis seedlings with isoxaben has several effects on the plant like ectopic lignification, changes in cell wall composition, alterations of gene expression and changes in phytohormone contents.

Microarray based analysis of isoxaben treated Arabidopsis thaliana seedlings showed changes in the expression of different genes involved in the trehalose 6-phosphate metabolism. Trehalose 6-phosphate (T6P) is a disaccharide of glucose and appears to be a regulator of carbon metabolism. It is a sugar signal and an essential component of the mechanisms that coordinate sugar metabolism with plant growth and development. T6P is synthesized from UDP-glucose and glucose 6-phosphate by the enzyme trehalose phosphate synthase (TPS). Trehalose 6-phosphate gets dephosphorylated by trehalose phosphate phopsphatase (TPP) into trehalose. The treatment of seedlings with Isoxaben results in expression changes of two trehalose-6 phosphate phosphatase genes (TPPD and TPPG) and one trehalose-6 phosphate synthase gene (TPS5). TPPD and TPPG are strongly up regulated, whereas TPS5 is down regulated 12 hours after isoxaben treatment. Measurement of the T6P content showed that the treatment with the herbicide results in lower T6P levels [analysis was performed by Dr. John Lunn, MPI-MP,Golm].

We hypothesize that T6P is part of the mechanism that coordinates carbon metabolism and cell wall metabolism during cell wall stress. To get new insights in the role of T6P, mutant lines with disturbed T6P signaling and mutants with altered T6P contents are analyzed in respect to changes in primary metabolism and cell wall composition. Transcriptome analysis via RNA Sequencing will identify candidate genes which are involved in the T6P signaling pathway, which connects CBI and the cell wall metabolism. In this way we try to get a better understanding of the role of T6P and the importance of this disaccharide in respect to the cell wall metabolism and changes in the cell wall under cell wall stress.


Utilization of plant secondary metabolism for production of high value products in plants

Plant secondary metabolites are essential components of the human diet, utilised as phytomedicines and routinely used as industrial raw materials and high-value fine chemicals. Chemically, secondary metabolites exhibit an enormous diversity and complexity, which makes their industrial chemical synthesis difficult and expensive. Agriculture and horticulture produces large quantities of plant biomass residues as by-products. Utilizing such by-products for extraction of secondary metabolites would lead to added value of crop production. Plants increase the production of secondary metabolites in response to abiotic and biotic stress.

In our BioSC NRW funded project “InducTomE- Induction of secondary metabolites in tomato by-products for extraction and economic evaluation of the model process”, we aim to identify abiotic stress treatments to induce the accumulation of two secondary metabolites (rutin and solanesol) in tomato by-products to high amounts. A conceptual process design is being developed for an extraction process and its economic feasibility is evaluated. In addition, co-induced secondary metabolites are being identified by metabolite profiling and RNAseq analysis and their market entry potential will also be evaluated. As a long-term prospect, the developed process concept will be transferable to other waste streams and metabolites, thereby playing a pivotal role in the successful development of a bioeconomy perspective.

The BMBF funded project „TaReCa - Tailoring of secondary metabolism in horticultural residuals and cascade utilization for a resource efficient production of valuable bioactive compounds“ aims at the development of a tailored cascade utilization of bell pepper residues, to exploit add-on value by combining the production of vegetables with subsequent extraction of valuable plant secondary metabolites (SM). The interdisciplinary project partners aim to explore the potential of tailoring secondary metabolism in residuals from bell pepper production by stresses applied in production greenhouses. The project will focus on the flavonoid cynaroside, which is of interest for the cosmetic, food and pharmaceutical industries due to its antioxidant, antimicrobial and cancer-preventive properties. As many SM have such beneficial properties, leaves and stems from stress-treated bell pepper plants will be screened for additional induced metabolites, followed by analysis of market potential and entry options/barriers as well as investigations on extractability. This generates the potential for the production of bioactive compounds for multiple market segments. The project drives the development of environmentally-friendly, economic extraction and purification processes which will be coupled to a potential utilization of the remaining plant material in a biorefinery to further increase the value chain. The double or even triple utilization of horticultural production chains for food and tailored compounds will generate novel, affordable and economically relevant products for industrial applications.