Research offers new insights into the salinity tolerance mechanisms of plants
Soil salinisation is what happens when excess salts accumulate in the root zone. The phenomenon, which reduces soil productivity, eventually making the land uncultivable, is a growing problem for agriculture worldwide, especially in the irrigated arid and semi-arid regions. “We know that the Salt Overly Sensitive(opens in new window) (SOS) pathway is one of the main regulatory systems responsible for sodium extrusion(opens in new window) in plants – a defence process that is activated by salt stress,” says Paula Ragel de la Torre, a researcher from the Centre for Organismal Studies(opens in new window) at Heidelberg University(opens in new window). “What we don’t know a lot about is the early steps in the sensing and regulation of the salt stress response.” The EU-funded sigNal project aims to fill this knowledge gap. Led by Ragel de la Torre, the project aimed to gain a better understanding of the salinity tolerance mechanisms of plants. “My goal was to show how salinity stress sensing is discriminated from other biotic(opens in new window) and abiotic(opens in new window) stresses that also lead to spikes in calcium,” explains Ragel de la Torre, who received support from Marie Skłodowska-Curie Actions(opens in new window).
Several important conclusions reached
Despite some delays caused by the COVID-19 pandemic, the project succeeded in reaching several important conclusions. First, researchers demonstrated that salt stress promotes an increase in cytosolic(opens in new window) pH(opens in new window) in the root tip. “This increase was higher than the one observed under the same osmotic stress(opens in new window) and high enough to be considered as having multiple cell consequences,” notes Ragel de la Torre. The research also suggests that the root tip works as a stress-sensing niche, where a combination of stress-specific changes in pH and calcium levels activate stress-specific responses. “I am proud to have proved the existence of changes in pH as a response of abiotic stresses,” she adds. “I am also proud to have planned, applied, managed and successfully run the project – all while learning and implementing state-of-the-art methods and increasing my collaboration network.” One issue the project was not able to confirm was whether changes in pH were needed to activate the SOS pathway or whether the putative salt bridge in SOS3(opens in new window), a family of calcium sensors, worked as a pH-sensing module. “Some results fit within our hypothesis, others proved to be more difficult to explain,” says Ragel de la Torre. “As with all scientific research, there’s more work to be done.”
Opening the door to additional research
The sigNal project has significantly enhanced researchers’ understanding of the mechanisms by which plant roots translate changes in soil into specific responses. Most importantly, it revealed new insights about the signalling of salt stress by linking salt and osmotic stresses to pH changes in a specific niche of the root. “The results of the sigNal project have opened the door to additional research in plant signalling pathways,” she concludes. “By shedding new light on the salinity tolerance mechanisms of plants, our findings will help researchers develop crop varieties adapted to suboptimal environmental conditions.”
