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

Abstract

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

Mono- and digalactosyldiacylglycerol composition of dinoflagellates. VI. Biochemical and genomic comparison of galactolipid biosynthesis betweenChromera velia(Chromerida), a photosynthetic alveolate with red algal plastid ancestry, and the dinoflagellate,Lingulodinium polyedrum

“…We make a similar hypothesis for the presence of 20:5 at the sn-1 position of the major forms of MGDG and DGDG in the Cluster 2 dinoflagellates identified by Gray et al (2009): that this trait has been obtained from its red algal plastid ancestor. However, with the exception of radiolabelling studies by Khozin et al (1997) and Sato & Moriyama (2007), little is known about the genes that encode the enzymes involved in the synthesis of galactolipids in the potential red algal ancestors of the plastids of C. velia and peridinin-containing dinoflagellates.…”

“…Conversely, the presence of 20:5 at the sn-2 position to form 20:5/20:5 MGDG and 20:5/20:5 DGDG was found to be very rare in peridinin-containing dinoflagellates, with only a few organisms possessing either lipid and only at relative abundances of less than 10% of the total galactolipids (Gray et al, 2009). Rather, in both of the clusters of peridinin-containing dinoflagellates identified by Gray et al (2009), it was observed that either 18:5 or 18:4 was present at the sn-2 position in the most abundant forms of MGDG and DGDG. In contrast, C. velia possessed 20:5, but neither 18:5 nor 18:4, at the sn-2 position.…”

“…In a comparison between C. velia and Cluster 2 dinoflagellates, including Lingulodinium polyedrum, Gray et al (2009) showed that these dinoflagellates possess 20:5 at the sn-1 position in the most abundant forms of MGDG and DGDG. Conversely, the presence of 20:5 at the sn-2 position to form 20:5/20:5 MGDG and 20:5/20:5 DGDG was found to be very rare in peridinin-containing dinoflagellates, with only a few organisms possessing either lipid and only at relative abundances of less than 10% of the total galactolipids (Gray et al, 2009). Rather, in both of the clusters of peridinin-containing dinoflagellates identified by Gray et al (2009), it was observed that either 18:5 or 18:4 was present at the sn-2 position in the most abundant forms of MGDG and DGDG.…”

“…For dinoflagellates containing C 20 and C 18 fatty acids in their galactolipids such as L. polyedrum, we have developed a potential model for galactolipid synthesis based on L. polyedrum's galactolipid composition (Gray et al, 2009) and gene annotations for galactolipid synthesis related genes (Roy & Morse, 2012). The identification of genes involved in the FASII synthase complex indicates that fatty acids are produced in the plastid through de novo synthesis, similar to what has been found in C. velia and other red algal plastids (Sato & Moriyama, 2007) (Fig.…”

“…Recently, peridinin-containing dinoflagellates, the largest group of photosynthetic dinoflagellates in terms of the number of known genera, were found via positive-ion electrospray/mass spectrometry (ESI/MS) analysis to be divided into two clusters according to the forms of MGDG and DGDG present (Gray et al, 2009). Cluster 1 dinoflagellates possessed major forms of MGDG and DGDG that contained C 18 fatty acids in the sn-1 and sn-2 positions (i.e.…”