Mono- and digalactosyldiacylglycerol composition of dinoflagellates. II. Lepidodinium chlorophorum, Karenia brevis, and Kryptoperidinium foliaceum, three dinoflagellates with aberrant plastids

The intact molecular forms of mono- and digalactosyldiacylglycerol (MGDG and DGDG, respectively), two important chloroplast membrane lipids, were determined via positive-ion electrospray ionization/mass spectrometry and positive-ion electrospray ionization/mass spectrometry/mass spectrometry for Lepidodinium chlorophorum, Karenia brevis and Kryptoperidinium foliaceum, three dinoflagellates with non-canonical plastids lacking the typical dinoflagellate carotenoid pigment peridinin, along with Tetraselmis sp., Emiliania huxleyi and Navicula perminuta, three algae with shared common ancestors, respectively, to these aberrant, tertiary plastids. Lepidodinium chlorophorum and K. brevis were found to possess 18:5/18:5 MGDG (sn-1/sn-2 regiochemistry), a form observed in several peridinin-containing dinoflagellates, along with forms of MGDG and DGDG not found in peridinin-containing taxa. Lepidodinium chlorophorum was found to possess 18:5/16:4 MGDG and 20:5/16:4 DGDG, and K. brevis was found to possess 18:5/14:0 MGDG and DGDG as forms of these lipids. Kryptoperidinium foliaceum was not observed to produce any C18 fatty acids within its forms of MGDG and DGDG; 20:5/16:3 MGDG and 20:5/16:2 DGDG were the two predominant forms. The MGDG and DGDG composition of the K. foliaceum/N. perminuta pair was almost an exact match, whereas in the L. chlorophorum/Tetraselmis sp. and K. brevis/E. huxleyi pairs, the MGDG and DGDG compositions were similar in some respects, but not others. The significance of these findings, along with the MGDG and DGDG composition of the putative tertiary endosymbionts, is discussed in the context of the evolution of the plastids of these organisms.