Characterization and expression analysis of the glycosyltransferase 64 family in rice (Oryza sativa)

The glycosyltransferase 64 (GT64) family is widely conserved in many species, including animals and plants. The functions of GT64 family genes in animals have been well characterized in the biosynthesis of extracellular heparan sulfate, whereas two GT64 members in Arabidopsis thaliana are involved in the glycosylation of plasma membrane glycosylinositol phosphorylceramides (GIPCs). GIPCs are the main components of plant sphingolipids and serve as important signal molecules in various developmental processes and stress responses. Rice (Oryza sativa), a model monocot plant, contains four GT64 members in its genome. Using phylogenetic analysis, 73 GT64s from 19 plant species were divided into three main groups. Each group can be represented by the three members in Arabidopsis and show a trend of monocot-eudicot divergence. A promoter and genomic variation analysis of GT64s in rice showed that various stress-related regulatory elements exist in their promoters, and many sequence variations were found between the two main rice subspecies, japonica and indica. Additionally, transmembrane domain and subcellular localization analyses revealed that these genes all encode membrane-bound glycosyltransferases and are localized to the Golgi apparatus. Finally, expression analysis of the four GT64 genes in rice, as assessed by quantitative real-time PCR, showed that they have distinct tissue-specific expression patterns and respond to different hormone treatments or abiotic stresses. Our results indicated that this family of genes may play a role in different stress responses and hormone signaling pathways in rice, which will provide fundamental information for further investigation of their functions in future.