Plant roots are much more than a simple absorption organ: they can adjust their structure to better cope with water stress.
Scientists studied 284 natural varieties of thale cress (
Arabidopsis thaliana) and discovered that the amount and distribution of suberin — a protective barrier deposited in roots — vary according to geographic origin and climate.
Coloration of suberin deposits in the roots of 5-day-old thale cress, observed by fluorescence microscopy. Signal intensity is represented by a color gradient from blue (low) to red (high).
© JP. Han @UNIGE
The scientists also identified a new regulatory gene for suberin linked to the water stress hormone. This study, published in the journal
Nature Plants, offers insights into understanding plant adaptation to their environment and making crops more resilient to arid conditions.
Roots are the main interface between plants and the soil. To regulate water and nutrient uptake, plants deposit in the endodermis — the cell layer surrounding the vessels that transport sap — a hydrophobic barrier made of suberin (the main component of cork). This barrier plays a central role in adaptation to environmental stresses such as drought, salinity, or mineral deficiencies.
Until now, knowledge about the regulation of suberin synthesis was mainly based on a reference line of thale cress, the model plant in plant genetics, grown in a laboratory greenhouse. Scientists largely ignored how its formation was controlled in natural contexts.
The team identified a previously unknown gene that plays a central role in the formation of this barrier.
Exploring natural diversity
The team led by Marie Barberon, associate professor in the Department of Plant Sciences of the Section of Biology of the Faculty of Science, focused on natural variations by analyzing the characteristics and genomes of 284 lines of thale cress from different regions of the world. Using a fluorescent dye, the Geneva team quantified the profile of suberin formation along the root in each of them. They observed a striking diversity in suberin deposition levels and profiles.
By correlating these characteristics with the climatic conditions of the regions of origin of the thale cress, the team found that suberin deposits are more significant in regions with high precipitation variability, drier conditions, and high temperatures.
"Our results indicate that the strengthening of the barrier is a natural adaptation to water stress, allowing better control of water exchanges with the soil," explains Jian-Pu Han, senior assistant in Prof. Barberon's lab and first author of the study.
Identification of a new genetic regulator
Through a 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 strengthens; when it is disrupted, the barrier forms less effectively," continues Jian-Pu Han. The biologists also discovered that this control mechanism is linked to abscisic acid (ABA), a plant hormone central to the response to environmental stresses, particularly water stress.
"Our results show that the modulation of hormonal responses affecting suberin deposition is a central element of plants' climate adaptation strategy," concludes Marie Barberon. By identifying a new genetic lever to adjust root properties, this study paves the way for developing crops more resistant to climate stresses.