Universidad
Politécnica de Madrid

A research team from the Consejo Superior de Investigaciones Científicas (CSIC) has participated in an international study that applies a new microscopy technique that make possible to observe at the cellular scale how plants protect themselves against excess sodium. The work, published in the journal Nature, describes the function of a key plant protein in the tolerance of plants to high salinity, which is a fundamental finding to study possible biotechnological solutions to the growing problem of excessive salt in crop soils, caused by the expansion of irrigation systems and an increasingly dry climate.

 

“The study has been possible thanks to the combination of an innovative microscopy technique that allows elemental analysis with subcellular resolution, called CryoNanoSIMS (Cryo Nanoscale Secondary Ion Mass Spectrometry) developed in Switzerland, and the fine analysis of the subcellular distribution of the SOS1 protein, performed by CSIC researchers,” explains Priya Ramakrishna, main researcher of the study, attached to the Ecole Polytechnique Fédérale de Lausanne and the University of Lausanne.

 

 

In addition to the Center for Plant Biotechnology and Genomics (CBGP) and the Institute of Plant Biochemistry and Photosynthesis (IBVF), both of the CSIC, several Swiss institutions have participated: the Ecole Polytechnique Fédérale de Lausanne, the University of Lausanne and the ETH Zurich.

SOS1, the key protein

Irrigation water contains small amounts of salts that are deposited in the upper layers of the soil and accumulate after water evaporation. Among these salts, sodium ions stand out for their toxic potential by competing with potassium ions, which is an essential macronutrient.

“The CSIC researchers involved in this study had already shown that the plant protein called SOS1 acts specifically in the transport of sodium across biological membranes. The known function of SOS1 is the expulsion of sodium accumulated in the cells, both back to the soil and for its distribution among the different organs of the plant through the conductive system,” explains José M. Pardo, CSIC researcher at IBVF.

Another fundamental mechanism for salinity tolerance is the sequestration of sodium ions in cellular compartments called vacuoles, where the cell is able to store large quantities of salts and avoid the intoxication of essential biochemical processes. However, the proteins responsible for the vacuolar accumulation of sodium had not been identified. “Now, with this work we have shown that SOS1 is also fundamental for this process, especially in poorly differentiated tissues where an effective conductive system has not yet formed to evacuate the accumulated sodium,” says Francisco Gámez-Arjona  CSIC researcher at IBVF.

“This finding reinforces the  importance of the SOS1 protein in plant salt tolerance and opens new avenues for its biotechnological exploitation, points out Francisco J. Quintero, director of the study at IBVF. “New avenues of research are now open to understand how the targeting of SOS1 towards the plasma membrane or towards the vacuolar membrane is controlled, and also to explore how this new function of SOS1 can be exploited to increase the detoxifying capacity of plants subjected to salt stress,” he adds.

“This work is a magnificent example of cross-fertilization between disciplines, because it is necessary to wait for a new development in the capacity of mineral analysis in the different cellular compartments to be able to demonstrate the function of SOS1 in sodium transport in vacuoles,” says Clara Sánchez, CSIC researcher at the CBGP.