The family of LSU-like proteins

Abstract

Plant response to sulfur deficiency results in extensive metabolic changes and can be monitored at various levels (transcriptome, proteome, metabolome) even before the occurrence of the first visible symptoms of sulfur starvation. The plant-specific LSU (RESPONSE TO LOW SULFUR) gene family is represented by four members in Arabidopsis thaliana (LSU1-4) and multiple members in other plant species. Three out of four LSU genes in Arabidopsis are induced in sulfur deficiency conditions. In tobacco, the LSU-like genes were characterized as UP9 (UPREGULATED BY SULFUR DEFICIT 9). The LSU-like proteins contain no characteristic domains that could help to identify their function. Despite moderate primary sequence conservation they share several common features, including small size, coiled-coil secondary structure and short conserved motifs located in particular positions. Although the precise function of these proteins is still unknown, there is some evidence that members of the LSU-like family are involved in plant response to environmental challenges, such as sulfur deficiency and possibly in plant immune responses. Interestingly, various bioinformatic approaches have identified these proteins as important hubs integrating signals from different environmental stimuli. In this paper we review a variety of published data about LSU gene expression, properties of lsu mutants and features of LSU proteins in the hope of shedding some light on their possible role in plant metabolism.