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

Abstract

Chromera velia is a recently discovered, photosynthetic, free-living alveolate that is the closest free-living relative to nonphotosynthetic apicomplexan parasites. Most plastids, regardless of their origin, have membranes composed chiefly of two galactolipids, mono-and digalactosyldiacylglycerol (MGDG and DGDG, respectively). Because of the hypothesized shared red algal origin between the plastids of C. velia and dinoflagellates, our primary objectives were to examine how growth temperature affects MGDG and DGDG composition via positive-ion electrospray/mass spectrometry (ESI/MS) and positive ion/electrospray/ mass spectrometry/mass spectrometry (ESI/MS/MS), and to examine galactolipid biosynthetic genes to determine if shared ancestry translates into shared MGDG and DGDG composition. When growing at 20°C, C. velia produces eicosapentaenoic acidrich 20:5(n-3)/20:5(n-3) (sn-1/sn-2) MGDG and 20:5(n-3)/20:5(n-3) DGDG as its primary galactolipids, with relative percentage compositions of approximately 35 and 60%, respectively. At 30°C these are lessened by approximately 5 and 8%, respectively, by the corresponding production of 20:5/20:4 forms of these lipids. The presence of 20:5 at the sn-1 position is similar to what has been observed previously in a cluster of peridinin-containing dinoflagellates, but the presence of 20:5(n-3) at the sn-2 position is extremely rare. Thus, the forms of MGDG and DGDG in C. velia displayed similarities and differences to what has been observed in peridinin-containing dinoflagellates, such as Lingulodinium polyedrum, which produces 20:5/18:5 and 20:5/18:4 as the major forms of MGDG and DGDG. We develop conceptual models from the galactolipids observed and galactolipid-relevant gene annotations to explain the presence of polyunsaturated fatty acid-containing MGDG and DGDG in both L. polyedrum and C. velia.

Separation and identification of lipids in the photosynthetic cousins of Apicomplexa Chromera velia and Vitrella brassicaformis

“…Monounsaturated FA with 18 carbons were recorded in both chromerids in two forms: C18:1 n‐7 and C18:1 n‐9. Contrary to Dahmen's group presenting an identification of galactolipids with non‐polyunsaturated FAs C18 in C. velia , FID methodology was able to found one type of FA C18:2 n‐6 and two types of FA C18:3 n‐6 and C18:3 n‐3. All these FAs are present in different groups of marine photosynthetic organisms .…”

Squishy lipids: Temperature effects on the betaine and galactolipid profiles of a C18/C18 peridinin‐containing dinoflagellate, Symbiodinium microadriaticum (Dinophyceae), isolated from the mangrove jellyfish, Cassiopea xamachana

“…We have found that like S. microadriaticum and species of Pyrocystis , C. velia also follows the pattern of modulating the sn ‐2 fatty acid of MGDG and DGDG, but rather than modulating a C 18 fatty acid it instead modulates 20:5 at 20°C to eicosatetraenoic (20:4) at 30°C (Dahmen et al . ). Thus, as we learn more about how dinoflagellates and their photosynthetic relatives respond to growth temperature with regard to their forms of MGDG and DGDG, we are finding that there are common adaptation mechanisms.…”

“…The presence of 16:0‐containing forms at 30°C does, however, agree with observations by Dahmen et al . () in the photosynthetic chromerid, Chromera velia Moore et al ., which produced 20:5/16:0 and 20:4/16:0 at 30°C but not 20°C. Similar results were observed by Adlerstein et al .…”

Temperature modulation and the presence of C20 fatty acids in mono‐ and digalactosyldiacylglycerol of Euglena gracilis and Lepocinclis acus: A modern interpretation of euglenid galactolipids using positive‐ion electrospray ionization/mass spectrometry

“…; Dahmen et al . ), it was found that the predominantly C 18 sn ‐2 fatty acids of MGDG and DGDG were modified to be less saturated at 30°C, whereas the predominantly C 20 sn ‐1 fatty acid had the same degrees of unsaturation at both temperatures. In H. ostrearia and P. tricornutum (Dodson et al .…”