Mono- and digalactosyldiacylglycerol composition of dinoflagellates. I. Peridinin-containing taxa

Two glycolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are components of chloroplast membranes. This study addresses the lack of information regarding the major intact forms of these glycolipids in photosynthetic dinoflagellates through the use of a full-scan positive-ion electrospray ionization/mass spectrometry (ESI/MS) survey of MGDG and DGDG in 35 peridinin-containing taxa from the class Dinophyceae. Further analysis using positive-ion electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS) was performed to determine the positional distribution of fatty acids associated with MGDG and DGDG. The dinoflagellates examined were divided into two clusters based on the forms of MGDG and DGDG present. The first possessed 18:5/18:4 MGDG (sn-1/sn-2), 18:5/18:5 MGDG, 18:4/18:4 DGDG, and 18:5/18:4 DGDG as major forms, and the second possessed 20:5/18:4 MGDG, 20:5/18:5 MGDG, 20:5/18:4 DGDG, and 20:5/18:5 DGDG as major forms. The differentiation between C18/C18 and C20/C18 glycolipids indicates differing biosynthetic pathways, as well as a possible evolutionary divergence between the two dinoflagellate clusters.