Identification and evolution of the plant sulfotransferase family

Sulfotransferases (SOTs, EC 2.8.2.-), which catalyze sulfate conjugation reactions, are widespread across prokaryotes and eukaryotes. However, the origin, classification and evolution history of SOTs in plants are not as well understood as those in animals and bacteria. In this study, a systematic analysis of an array of sequenced genomes revealed that SOTs were ubiquitously distributed in green plants (Viridiplantae). Phylogenetic analysis classified plant SOTs into three subfamilies, including SULTs (soluble sulfotransferases), TPSTs (tyrosylprotein sulfotransferases), and NFSTs (nodulation factor sulfotransferase). Notably, CHSTs (carbohydrate sulfotransferases), abundant in animals, algae and bacteria, were not found in land plants. High-throughput screening algorithms, phylogenetic and gene structure analyses indicated that land plants might acquire NFSTs through horizontal gene transfer (HGT) from bacteria to green algae. In contrast to the low gene number of TPSTs and NFSTs in land plants, the number of SULTs varied greatly among species. The absence of SULTs resulted in a significantly reduced gene number of SOTs in Cucurbitaceae, whereas the recent expansion of SULTs, mainly driven by tandem duplication (TD), caused a significant increase in SOT gene number in Begoniaceae. The significant variation in the gene number of SULTs across species, along with their evolutionary branching patterns, indicated lineage-specific duplication or contraction of SULTs, which profoundly influenced the production of sulfated metabolites during the diversification of monocots and core eudicots. This study provided the first comprehensive phylogenetic, classification and evolutionary analysis of SOTs in green plants across a broad taxonomic range.