Novel insights into the diversity of the sulfurtransferase family in photosynthetic organisms with emphasis on oak.

Sulfurtransferases (STRs) constitute a large and complex protein family characterized by the presence of a rhodanese domain and implicated in diverse molecular and signaling processes as sulfur carriers. Although sulfurtransferases are present in the three domains of life and share evolutionary relationships, a high variability exists at different levels including the protein length and active site sequence, the presence of an indispensable catalytic cysteine residue, the domain arrangement and the subcellular localization. Because only Arabidopsis thaliana sequences have been inventoried so far, this paper aims at providing a detailed classification and inventory of evolutionary features of this family in photosynthetic organisms using comparative genomics, focusing on the oak genome. Based on the expansion of STRs in higher photosynthetic organisms, we classified the STR family in nine clusters depending on their primary sequence and domain arrangement. We found that oak possesses at least one isoform in all defined clusters and that clusters IV, V and VI contain plant-specific isoforms that are located mostly in chloroplasts. The novel classification proposed here provides the basis for functional genomics approaches in order to dissect the biochemical characteristics and physiological functions of individual STR representatives.