Molecular mechanisms in plants revealed to distinguish between essential and toxic compounds

José María García-Mina, researcher at the Institute of Biodiversity and Environment and professor at the Faculty of Sciences, has collaborated in a study, led by the Spanish National Research Council (CSIC), which has identified for the first time the molecular mechanisms used by plants to distinguish between phosphate, an essential nutrient for living beings, and arsenic, a carcinogenic compound present in most soils and waters.

The work, published in the journal Molecular Plant, provides insight into how plants distinguish between beneficial nutrients and toxic elements with chemical similarities. This finding may help to obtain safer and healthier foods enriched in essential nutrients.

In plants, arsenate and arsenite, the most abundant chemical forms of arsenic present in the biosphere, are easily incorporated into cells, allowing the metalloid to enter the food chain and thus threatening human health. "Arsenic in nature is mainly found as arsenate, a molecule very similar to phosphate, with which it shares the transporter of entry of these compounds into cells," explains Antonio Leyva, CSIC researcher at the National Center for Biotechnology (CNB-CSIC) and leader in this work. "While phosphate is metabolized by plants, arsenate is rapidly transformed into arsenite, a compound even more toxic than arsenate, but which, according to the results obtained, acts as a sensor and activates the defense response to poisoning," he adds.

Plant roots face continuous changes in the soil environment and require rapid and strict control of transporters to modulate the absorption of nutrients and toxic compounds. "In the presence of arsenate, the first reaction of plants is to prevent its entry by 'shutting down' the common transporter," highlights Cristina Navarro, also a CSIC scientist at CNB-CSIC. "This repression leads the plant to a paradoxical situation of phosphate fasting that compromises its survival, but at the same time prevents arsenic intoxication. Plants have a sophisticated mechanism of 'on and off' of the transporter very precise that is regulated depending on the detoxification capacity of the plant," says the researcher.

Cristian Mateo-Elizalde, CNB-CSIC researcher and co-author of the study, stresses "the importance of obtaining foods enriched in essential elements, such as iron, zinc or magnesium, as opposed to others that are highly toxic for animals and humans, such as mercury, cadmium or arsenic, all of which are present in nature". The scientists point out that knowing the mechanisms for discriminating between toxic compounds and other essential ones is fundamental in agriculture to obtain safer foods enriched in essential nutrients.

Bibliographic reference

Navarro C., Mateo-Elizalde C., Mohan T.C., Sánchez-Bermejo E., Urrutia O., Fernández-Muñiz M.N., García-Mina J.M., Muñoz R., Paz-Ares J., Castrillo G. and Leyva A. Arsenite Provides A Selective Signal that Coordinates Arsenate Uptake and Detoxification Involving Regulation of PHR1 Stability in Arabidopsis thaliana. Molecular Plant. DOI: 10.1016/j.molp.2021.05.020