Rhizosphere

Plants engage in numerous interactions with both beneficial and harmful organisms. These can be bacteria or fungi but also other plant species, such as Orobanchaceae species. It is of great importance for plants to attract friends and repel foes. This intra- and inter-kingdom communication occurs through molecular signaling pathways involving the secretion and sensing of various metabolites and proteins. We are especially interested in this molecular communication and focus on biological systems of importance to increase the sustainability of our agriculture.

Soybean growth in Flanders

Soybean (Glycine max) is nowadays one of the most important protein sources for food and feed. Belgium completely depends on the import of soybean and its derived products with a yearly amount of approximately 800.000 ton from which 65% is imported from high risk countries (e.g., Argentina, Brazil) leaving a land footprint of 2 million hectares through, amongst others, deforestation and forest degradation. To reduce this dependency and to develop social responsible protein products, Belgium’s agriculture would strongly benefit from local soybean production. However, the cultivation of protein rich soybean in Belgium encounters the challenge of the colder climate. Hundreds of soybean varieties have already been bred for growth in these cold Belgian temperatures but to guarantee consistent high protein rich beans plants need to efficiently interact with nitrogen-fixing bacteria in root nodules. When the current commercial inoculants are used this interaction is inhibited by cold growing conditions leading to insufficient protein yields for human food.

Furthermore, the use of soybean-derived proteins for human consumption offers a solution for other major worldwide environmental challenges such as nitrogen pollution and soil quality as legumes act as natural nitrogen fertilizers and green indicators of soil nutrition.

We search for endogenous rhizobia in Flemish soils, able to efficiently nodulate soybean in cold temperatures as well to raise public awareness about the benefits of legumes for sustainable agriculture. We will involve 1000 citizens by, on the one side, letting them grow soybeans in their gardens to find nodules and characterize phenotypic traits, and, on the other side, letting them participating into surveys to gather specific information on the management of each garden soil.

Plant growth promoting rhizobacteria

Plant roots are colonized by vast amounts of microorganisms, of which many facilitate plant growth. The underlying mechanisms of plant growth promotion can have several causes: it can occur through protection against pathogens, pests or harsh abiotic environments, through the facilitation of nutrient uptake or through an effect on plant hormone levels and signaling. We use a combination of cultivation dependent and independent approaches to identify new biologicals that boost plant growth under various abiotic stresses such as salinity, drought and cold. The crops understudy are wheat, maize, tomato and lettuce.

We also aim at identifying the plant molecular networks on which PGPR’s impinge to boost plant growth and yield. By using transcriptomic and proteomic approaches combined with functional analysis, in Arabidopsis thaliana but importantly also in maize and wheat, we visualize these networks and identify important signaling hubs and markers.

Arbuscular mycorrhiza

Arbuscular mycorrhizal (AM) fungi form mutualistic associations with more than 80% of all land plants. This symbiotic interaction is established by a strictly controlled exchange of signals whereby the fungus also needs to repress the plant’s defense response. From the plant pathology field, we know that the secretion of small effector proteins can achieve this. Interestingly, AM fungi are also predicted to secrete effectors but little is known about their role inside the plant as well as their interacting plant proteins during AM symbiosis.

In this research, we focus on the model species Rhizophagus irregularis with its host tomato. We aim to learn how these AM effectors function inside the host plant, by identifying their plant protein partners and elucidating how this interaction alters plant growth during mycorrhization under control and diverse stress conditions such as drought and nutrient limitations. Via high-throughput analyses of direct interactions by means of Y2H-Seq as well as complex purification methods such as GFP trapping and proximity labeling, we want to identify the protein-protein interplay during the development of AMF-tomato symbiosis.

Strigolactone action in the Rhizosphere

Plants secrete a variety of compounds into the rhizosphere to control the interactions with surrounding organisms. One group of these compounds are strigolactons (SLs). They are known for the induction of arbuscular mycorrhization (AM) to overcome nutrient limitations. Furthermore, SLs are used as a recognition signal by parasitic weeds such as Orobanche and Striga spp to ensure germination in the presence of the host, leading to significant crop losses world-wide. Besides, SLs also act as plant hormones influencing plant architecture through the fine-tuning of shoot branching and root growth. We want to elucidate SL signaling networks in order to understand their role both as a plant hormone and during parasitic weed germination. To achieve this goal, we combine various approaches to study protein-protein, protein-DNA and protein-metabolite interactions.. In-depth analysis of identified signaling components will provide new insights in how this group of hormones exerts its function in plants and in the rhizosphere.

Publications

Beirinckx, S., Viaene, T., Haegeman, A., Debode, J., Amery, F., Vandenabeele, S., Nelissen, H., Inzé, D., Tito, R., Raes, J., De Tender, C., Goormachtig, S.
Luo, D., Langendries, S., Garcia Mendez, S., De Ryck, J., Liu, D., Beirinckx, S., Willems, A., Russinova, E., Debode, J., Goormachtig, S.
Gautrat P., Mortier, V., Laffont, C., De Keyser, A., Fromentin, J., Frugier, F., Goormachtig, S.
Struk, S., Jacobs, A., Martín-Fontecha, ES., Gevaert, K., Cubas, P., Goormachtig, S.
Sare, AR., Stouvenakers, G., Eck, M., Lampens, A., Goormachtig, S., Jijakli, MH., Massart, S.

Resources