What is the role of exogenous NO for plants, microbes, and their interactions in soil?

• Applicants: Professor Dr. Nicolas Brüggemann; Professor Dr. Klaus Butterbach-Bahl
• Subject Area: Soil Sciences ; Microbial Ecology and Applied Microbiology ; Ecology of Land Use
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446183421

Nitric oxide (NO) is a nitrogen trace gas which is produced by microbes and physico-chemical processes in soils as well as by physiological processes in plants. NO is considered as a major physiological mediator with many functions such as stimulation of the plant innate immune system, stimulation of plant morphogenesis and nutrition, responses to abiotic stresses, antimicrobial agent against pathogens, regulation of nitrogen cycling processes in microorganisms, etc. Despite the relatively high emission of NO quantified from soil and the high concentrations of NO within the soil profile, it remains largely unexplored how organisms below and above ground as well as their interactions respond to variations in soil air and atmospheric NO (exogenous) concentrations. Considering the versatile role of NO on both microorganisms and plants, investigating the role of NO in plant-soil systems can lead to a greater understanding of plant-microbe and microbe-microbe interactions. Such interactions and feedbacks between plants and microbial communities are of importance for many soil functions such as plant productivity and health, soil filtration, climate regulation, and nutrient cycling and have rapidly gained attention since they can offer promising avenues for practical application.The overall objective of this project is to assess the importance of exogenous NO produced either by plants or by soil processes on soil microorganisms and plants as well as their interactions. Our overarching hypothesis is that soil NO concentrations and NO emissions from soil are not only of outstanding importance for atmospheric chemistry but can also affect microbes and plants and therefore regulate plant-soil interactions as well as soil functions. More specifically, the different hypotheses associated with our objective are:(H1) Plants can detect exogenous NO in soil air and the atmosphere with consequences for plant health and nutrition, (H2) Exogenous NO can affect microbial community composition and interactions, (H3) NO is a regulator of key microbial activities related to soil N- and C-cycling. Therefore, exogenous NO can affect both the abundance and the activity of the corresponding soil microbial guilds as well as indirectly N-acquisition, N-transformation and organic matter decomposition by other soil microorganisms.(H4) NO metabolism/ NO production in plants can affect microbial C-/ N-processes in the rhizosphere.In this project, a model soil and the model plant Arabidopsis thaliana is used. Within a series of defined incubation experiments, we will expose soil micro-organisms, plants, plant-soil systems to defined exogenous NO concentrations and will study physiological, functional and process changes in plants and microbes to NO concentration changes. We will focus on nitrogen-cycling not only because NO is inherently linked to this cycle but also because nitrogen is the nutrient most strongly limiting plant growth in many terrestrial ecosystems.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Co-Investigators: Privatdozent Dr. Michael Dannenmann; Dr. Benjamin Wolf
• Cooperation Partner: Professor Dr. Laurent Philippot