Researchers have uncovered two distinct adaptive strategies to soil salinity in different populations of the wild plant species, Brassica fruticulosa, located along the coast of Catalonia, and have identified the specific genes involved. This research aims to enhance the resilience of agricultural plants within the same family, such as rapeseed and mustard, against the globally pressing issue of soil salinization.
Researchers from the Universitat Autònoma de Barcelona (UAB) have identified two distinct adaptive strategies to soil salinity in different populations of the wild plant species Brassica fruticulosa found in the coastal region of Catalonia and pinpointed the relevant genes. The findings will aid in exploring methods to boost the resilience of agricultural species from the same plant family, including rapeseed and mustard, in response to the significant global challenge of soil salinization.
The recent study was published in Proceedings of the National Academy of Sciences (PNAS) and was conducted by researchers SÃlvia Busoms, Glòria Escolà , and Charlotte Poschenrieder from the UAB Plant Physiology Lab, working alongside teams from the University of Nottingham (UK), the Max Planck Institute for Biology (Germany), and Charles University in Prague (Czech Republic).
In recent years, UAB researchers, in collaboration with the University of Nottingham, have developed a study model along the Catalan coast to analyze how environmental factors such as salinity interact with the adaptation of wild populations from the Brassicaceae family. While earlier studies focused on Arabidopsis thaliana, a commonly used model in biological research, this time the attention turned to Brassica fruticulosa, which is more closely related genetically and morphologically to cultivated species like rapeseed (Brassica napus) and mustard (Sinapis alba).
The research revealed that coastal populations of B. fruticulosa in Catalonia use two different approaches to cope with soil salinity. Those in the northern region (Cap de Creus) manage to limit the transport of sodium from roots to shoots, thereby protecting the aboveground parts of the plant. Conversely, populations from the central area tend to accumulate sodium in their leaves but possess effective mechanisms for osmotic adjustment and compartmentalization, allowing them to endure high sodium levels.
The researchers were surprised to find that two populations of the same species, located close to each other, had evolved in such distinct ways under similar environmental conditions. “Typically, one expects species facing similar stressors to evolve in comparable manners. However, despite soil salinity being a significant selective factor in the coastal regions of Catalonia, other influences must have affected the recent evolution of this Brassicaceae species,” SÃlvia Busoms points out. Such divergence in plant populations within close geographical proximity is rare, not necessarily due to its unusual nature, but rather because most studies examine larger geographical scales.
The Tramontane wind may explain this divergence
The researchers carefully analyzed soil characteristics and climatic conditions across all populations. The only notable difference found was in evapotranspiration rates, which were higher in the northern region due to the influence of the Tramontane wind that frequently sweeps through. “With increased evapotranspiration, plants absorb more water along with sodium if they lack sodium-exclusion mechanisms. Thus, the strategies employed by central coastal plants may not suffice in the harsher conditions found further north. We hypothesize that despite being neighboring populations, the northern B. fruticulosa evolved differently to handle both high salinity and elevated evapotranspiration,” notes Charlotte Poschenrieder.
To delve into the genetic underpinnings of the two adaptive strategies identified, researchers first established a reference genome for B. fruticulosa. This effort contributes to expanding the catalog of reference genomes for eukaryotic species from Catalan-speaking regions as part of the Earth Biogenome Project, facilitating future research on this species. They subsequently sequenced 18 populations and conducted genetic and transcriptomic analyses that confirmed the observed strategies and identified candidate genes linked to salinity tolerance.
Soil salinity is a significant threat to agriculture worldwide, with its negative effects heightened in already impoverished soils, such as those in the Mediterranean region. Understanding how plants in these areas adapt to salt is crucial for enhancing the resilience of cultivated species facing shifting environmental conditions. “This research positions B. fruticulosa as a valuable source of favorable gene variants and highlights the genetic diversity present in Catalonia as a key model for studying adaptations to saline soils,” the researchers conclude.
