Salinity is one of the major abiotic stresses that adversely affect the crop productivity and growth of the whole plant. The halophytic Prosopis strombulifera (Fabaceae) shrub is a useful plant model to study the molecular and physiological mechanisms involved in salinity tolerance. In this work, the isolation and characterization of the mRNA for a new atypical LEA protein (PsLEA3) is reported. PsLEA3 has alanine as the most abundant amino acid followed by serine. This characteristic is different from typical LEA proteins which have high glycine content. PsLEA3 shows a negative average of hydropathy and remains localized in the chloroplast. The phylogenetic relationship between related LEA proteins and PsLEA3 showed that this protein belongs to the same group as a LEA protein of Arabidopsis. Northern analysis revealed a differential expression of this atypical LEA mRNA in P. strombulifera plants under NaCl and Na 2 SO 4 treatments. Over-expression in roots of Na 2 SO 4 -treated plants from W o -1.9 MPa was associated with abscisic acid (ABA) and its conjugate (ABA-glucose ester) accumulation as well as with the root length of these plants, showing an inhibition and toxicity induced by sulphate anion present in the medium.