Plant roots are far more than simple absorption organs: they can adjust their structure to better cope with water stress. Scientists at the University of Geneva (UNIGE), in collaboration with the University of Lausanne (UNIL), studied 284 natural varieties of Arabidopsis thaliana and discovered that the amount and distribution of suberin – a protective barrier deposited in roots – vary according to geographic origin and climate. The researchers also identified a new gene regulating suberin that is linked to the water-stress hormone. Published in the journal Nature Plants, this study provides new insights into how plants adapt to their environment and opens new avenues for developing crops that are more resilient to arid conditions.
Roots form the main interface between plants and the soil. To regulate the uptake of water and nutrients, plants deposit a hydrophobic barrier made of suberin (the main component of cork) in the endodermis – the layer of cells surrounding the vessels that transport sap. This barrier plays a central role in adaptation to environmental constraints such as drought, salinity, or mineral deficiencies.
Until now, knowledge about the regulation of suberin synthesis was based mainly on a reference line of Arabidopsis thaliana, the model plant in plant genetics, grown in laboratory greenhouses. Scientists largely ignored how its formation was controlled in natural contexts.
Exploring natural diversity
The team led by Marie Barberon, associate professor in the Department of Plant Sciences in the Section of Biology at the Faculty of Science, focused on natural variation by analyzing the traits and genomes of 284 Arabidopsis lines originating from different regions of the world. Using a fluorescent dye, the Geneva team quantified the pattern of suberin formation along the root in each of them. The researchers observed striking diversity in the levels and patterns of suberin deposition.
By correlating these traits with the climatic conditions of the regions where the Arabidopsis lines originated, the team found that suberin deposition is greater in regions characterized by high variability in rainfall, drier conditions, and higher temperatures. “Our results suggest that strengthening the barrier is a natural adaptation to water stress, enabling better control of water exchange with the soil,” explains Jian-Pu Han, research and teaching fellow in Prof. Barberon’s laboratory and first author of the study.
Identifying a new genetic regulator
Through genome-wide genetic analysis, the team identified a previously unknown gene that plays a central role in the formation of this barrier. “This gene acts as a key regulator of suberin: when it is more active, the barrier becomes stronger; when it is disrupted, it forms less efficiently,” Jian-Pu Han continues. The biologists also discovered that this control mechanism is linked to abscisic acid (ABA), a plant hormone that plays a central role in responses to environmental stresses, particularly water stress.
“Our results show that modulation of hormonal responses affecting suberin deposition is a central element of plants’ adaptation strategy to climate,” concludes Marie Barberon. By identifying a new genetic lever that can adjust root properties, this study opens the way to the development of crops that are more resistant to climate stress.