Sulfur is an essential macronutrient for plants and a constituent of relevant biomolecules, such as the amino acids methionine and cysteine, the antioxidant glutathione, glucosinolates, coenzymes and prosthetic groups. As such, the availability of S, the main source of sulfur in soils, is an important determinant of plant growth, yield and quality.

LSUs are small proteins of approximately 90 -100 amino acids. Molecular modeling of LSU structures in Arabidopsis shows that these small proteins have a coiled-coil structure. In this work, we performed a genome-wide identification and evolutionary analysis of LSU genes in plants. Our results suggest that different genes from the S assimilation pathway, the LSU gene family, arose in Spermatophyta. Phylogenetic analysis revealed three major LSU groups in angiosperms, two for dicotyledons and one group for monocotyledons. Moreover, we analyzed the expression of LSUs in one representative species of each phylogenetic group and found a conserved response to S deficiency, suggesting that these genes might play a key role in sulfur-stress responses. Overall, these data indicate that LSU genes are evolutionarily conserved in angiosperms, and members of this family might play a significant role in the regulation of S transport and assimilation.