Discovery of Novel Neutral Glycosphingolipids in Cereal Crops: Rapid Profiling Using Reversed-Phased HPLC–ESI–QqTOF with Parallel Reaction Monitoring

This study explores the sphingolipid class of oligohexosylceramides (OHCs), a rarely studied group, in barley ( Hordeum vulgare L.) through a new lipidomics approach. Profiling identified 45 OHCs in barley ( Hordeum vulgare L.), elucidating their fatty acid (FA), long-chain base (LCB) and sugar residue compositions; and was accomplished by monophasic extraction followed by reverse-phased high performance liquid chromatography electrospray ionisation quadrupole-time-of-flight tandem mass spectrometry (HPLC–ESI–QqTOF–MS/MS) employing parallel reaction monitoring (PRM). Results revealed unknown ceramide species and highlighted distinctive FA and LCB compositions when compared to other sphingolipid classes. Structurally, the OHCs featured predominantly trihydroxy LCBs associated with hydroxylated FAs and oligohexosyl residues consisting of two–five glucose units in a linear 1 → 4 linkage. A survey found OHCs in tissues of major cereal crops while noting their absence in conventional dicot model plants. This study found salinity stress had only minor effects on the OHC profile in barley roots, leaving questions about their precise functions in plant biology unanswered.