Galactinol synthase across evolutionary diverse taxa: Functional preference for higher plants?

Galactinol synthase (GolS), a GT8 family glycosyltransferase, synthesizes galactinol and raffinose series of oligosaccharides (RFOs). Identification and analysis of conserved domains in GTs among evolutionarily diverse taxa, structure prediction by homology modeling and determination of substrate binding pocket followed by phylogenetic analysis of GolS sequences establish presence of functional GolS predominantly in higher plants, fungi having the closest possible ancestral sequences. Evolutionary preference for a functional GolS expression in higher plants might have arisen in response to the need for galactinol and RFO synthesis to combat abiotic stress, in contrast to other organisms lacking functional GolS for such functions.

► Galactinol synthase (GolS) represents a monospecific clade among the GT8 (Glycosyltransferase 8) enzymes.
► The 3-D structure of GolS shows a high structural flexibility which is significant in its evolution.
► GolS has evolved primarily as a plant-specific enzyme with a probable fungal ancestry.
► Expression of GolS is linked with abiotic stress.