Degradation of glycosylinositol phosphoceramide during plant tissue homogenization

A convenient method for the determination of plant sphingolipids (glycosylinositol phosphoceramide, GIPC; glucosylceramide, GluCer; phytoceramide 1-phosphate, PC1P and phytoceramide, PCer) was developed. This method includes the extraction of lipids using 1-butanol, alkali hydrolysis with methylamine and separation by TLC. The amounts of sphingolipids in the sample were determined based on the relative intensities of standard sphingolipids visualized by primulin/UV on TLC. Using this method, we found that almost all GIPCs were degraded in response to tissue homogenization in cruciferous plants (cabbage, broccoli and Arabidopsis thaliana). The decrease in GIPCs was compensated for by increases in PC1P and PCer, indicating that GIPC was degraded by hydrolysis at the D and C positions of GIPC, respectively. In carrot roots and leaves, most of GIPC degradation was compensated for by an increase in PCer. In rice roots, the decrease in GIPCs was not fully explained by the increases in PC1P and PCer, indicating that enzymes other than phospholipase C and D activities operated. As the visualization of lipids on TLC is useful for detecting the appearance or disappearance of lipids, this method will be available for the characterization of metabolism of sphingolipids in plants.