Prof. Tonni Grube Andersen - Molecular Biology of Plants
How do roots control exchange with their environment?
Plants live in constant contact with a complex and dynamic soil environment. Through their roots, they must take up water and nutrients, interact with beneficial microbes, and defend against pathogens. At the same time, they must prevent uncontrolled exchange that would disrupt their internal balance. How plants achieve this selective interaction with their surroundings remains a central question in plant biology.
A passage cell and associated “hub” expression pattern in Arabidopsis thaliana. Cell outlines are seen in grey, suberized endodermal cells in yellow. The red colour depicts expression of a gene that is present in the vasculature, but spreads into the passage cell and surrounding cells in the outer cortex layer. The insert shows a cross section of the root in the place of the passage cell.
Rather than interacting uniformly with the soil, roots appear to define specific locations where exchange is permitted. This implies that plants actively control where interaction occurs, not just how it is regulated. Understanding this spatial organization is at the core of our research.
Our work has identified specialized root cell types, known as passage cells, that occur at defined positions along the xylem axis and respond to environmental cues. These cells represent localized sites of interaction between the plant and its surroundings and provide a powerful entry point to study how exchange is organized at cellular resolution. More broadly, we investigate how root barrier systems, including suberin and the Casparian strip, are dynamically established and remodeled to create spatially distinct domains of interaction.
To address these questions, we combine high-resolution fluorescence imaging, near-native physiological setups, microfluidics, and transcriptomic and translatomic approaches. This enables us to study plant–environment interactions with high spatial and temporal resolution, linking single-cell behavior to whole-root function.
While much of our work is performed in the model plant Arabidopsis thaliana, we extend our research into Lotus japonicus, a legume that forms symbiotic root nodules. These nodules represent an extreme example of controlled exchange: they host nitrogen-fixing bacteria while maintaining tight regulation of gas and nutrient transport. Our work has shown that root barrier systems are essential for this process, suggesting that nodules are not exempt from barrier control but instead rely on its precise spatial reorganization.
Ultimately, our goal is to uncover the principles by which plants define where and how exchange with the environment occurs. From an applied perspective, this knowledge has the potential to improve nutrient use efficiency, enhance beneficial microbial interactions, and increase crop resilience under changing environmental conditions.