Genome-Wide Identification, Evolutionary and Expression Analyses of the GALACTINOL SYNTHASE Gene Family in Rapeseed and Tobacco

Abstract

Galactinol synthase (GolS) is a key enzyme in raffinose family oligosaccharide (RFO) biosynthesis. The finding that GolS accumulates in plants exposed to abiotic stresses indicates RFOs function in environmental adaptation. However, the evolutionary relationships and biological functions of GolS family in rapeseed (<i>Brassica napus</i>) and tobacco (<i>Nicotiana tabacum</i>) remain unclear. In this study, we identified 20 <i>BnGolS</i> and 9 <i>NtGolS</i> genes. Subcellular localization predictions showed that most of the proteins are localized to the cytoplasm. Phylogenetic analysis identified a lost event of an ancient GolS copy in the Solanaceae and an ancient duplication event leading to evolution of <i>GolS4/7</i> in the Brassicaceae. The three-dimensional structures of two GolS proteins were conserved, with an important DxD motif for binding to UDP-galactose (uridine diphosphate-galactose) and inositol. Expression profile analysis indicated that <i>BnGolS</i> and <i>NtGolS</i> genes were expressed in most tissues and highly expressed in one or two specific tissues. Hormone treatments strongly induced the expression of most <i>BnGolS</i> genes and homologous genes in the same subfamilies exhibited divergent-induced expression. Our study provides a comprehensive evolutionary analysis of <i>GolS</i> genes among the Brassicaceae and Solanaceae as well as an insight into the biological function of <i>GolS</i> genes in hormone response in plants.