Characterization and expression analysis of inositolphosphorylceramide synthase family genes in rice (Oryza sativa L.)

Genes encoding inositolphosphorylceramide synthase (IPCS), which play essential roles in sphingolipid biosynthesis, have been known to be widely distributed in plants. However, reports on identification, expression, and function analysis of plant IPCS family genes are very limited. In this study, a total of three OsIPCS genes were identified in the rice database, and their full-length coding regions were amplified by RT-PCR. These genes had 12–13 exons, and they encoded proteins of 313–326 amino acids with molecular mass of 35.8–37.6 kDa and isoelectric point of 10.99–12.61. Importantly, two typical and conserved motifs (D3 and D4) in plants were found in all the three putative OsIPCS proteins, indicating high similarity of OsIPCSs to the other plant IPCS proteins, which were confirmed by phylogenetic analysis. The transcripts of OsIPCS genes appeared in different rice organs including seedling roots, stems and leaves, and young panicles, but each gene showed a unique organ-specific expression pattern. Meanwhile, we found that all the three OsIPCS genes showed responses to stresses like drought, cold and salt, but their expression patterns were also to some extent different under stress treatments. Especially, under cold stress, OsIPCS1 and OsIPCS2 were significantly up-regulated in roots and stems but down-regulated in leaves, while OsIPCS3 was significantly up-regulated in all the measured organs. Actually, putative abiotic-stress regulatory elements were identified in the promoters of these genes. Our data suggest that OsIPCS genes should play important roles during rice growth and adversity adaptation.