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Finding of vegetal species suitable for ecologic restoration in arid climates is a primary goal of most of the governmental and private companies for fighting against the desertification and the recovery of contaminated soils. The Prosopis genus, a desert woody leguminous, with a wide distribution around the world, represents a very interesting source of highly tolerant and adaptable trees for revegetation and bioremediation of soils contaminated with metal and metalloids (metal(loid)s). The aim of the present work was to evaluate the South American representative of this genus, P. alba, as a possible solution for restoration of soils contaminated with mercury and arsenic. For this, we assessed possible tolerance mechanisms against both metal (loid) s by means of the evaluation of bioaccumulation behaviors and expression changes in metal (loid) tolerance genes. The results revealed that P. alba was able to tolerate high metal (loid) concentrations, related with the accumulation of high quantities of arsenic and mercury in the roots, with bioaccumulation factors of 2, 8 and 3, 1 respectively. Moreover, changes in the expression levels of the gene codifying for the metal transporter NRAMP2b was also observed after the exposure to the metal (loid) s, decreasing ten times for arsenic and three times for mercury. All of these results revealed the existence of cellular mechanisms that allow P. Alba to tolerate and accumulate high quantities of arsenic and mercury diluted into the substrate, making it a promising prospect for the treatment of contaminated soils.

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