Galactinol Synthase Gene Family in Angiosperms: Insights on Expression and Evolution

Galactinol synthase (GolS) is a family 8 glycosyl transferase that uses myo-inositol and galactose to produce galactinol, a raffinose precursor sugar. Biotechnological approaches manipulating GolS expression are well known, since raffinose family oligosaccharides are compatible solutes involved in mechanisms of adaptation to stress tolerance; evolutionary aspects of this gene family still are poorly understood. In this work, we depicted genomic and evolutionary aspects of GolS gene family in angiosperm genomes. We selected 20 plant genomes for analysis: six monocots and 14 eudicots. We found a range from 1 to 3 GolS genes in monocots and 5 to 10 genes in dicots. All GolS proteins showed the conserved domain GT8 and most sequences presented a conserved C-terminal portion. GolS genes encode proteins ranging from 303 to 364 amino acids, and all members are under positive selection, with a predominance of synonymous substitutions in eudicots. The phylogenetic tree divided GolS into two main groups, which separated mono and eudicots. According to RNA sequencing results in coffee and sorghum, we could identify that each member of GolS gene family has a tissue-specific expression profile and in sugarcane, GolS genes are induced by drought. Our results indicate a distinct pattern of GolS evolution among angiosperms, suggesting an expansion of GolS gene family in eudicots mediated by tandem and segmental duplications. We can infer, preliminarily, based on transcriptional profiles and phylogenetic analyses, that each GolS member has a specific role in plant metabolism and development.