Characterization of the Betaine Lipids, Diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) and Diaclyglycerylhydroxymethyl-N,N,N-trimethyl-β-alanine (DGTA), in Brown- and Green-Pigmented Raphidophytes
Leblond, Jeffrey D.; Dahmen, Aaron S.; Dodson, Vernon J.; Dahmen, Jeremy L.
Raphidophytes are a small class of harmful marine and freshwater algae that have large environmental and economic consequences around the globe. Recently, an examination of the composition of chloroplast-based galactolipids in brown-pigmented, marine taxa and the green-pigmented, freshwater Gonyostomum semen, found that G. semen possesses abundant quantities of mono- and digalactosyldiacylglycerol (MGDG and DGDG, respectively) which contain octadecatrienoic acid (18:3). This particular fatty acid is often indicative of a green algal plastid ancestry, and, as such, forms of MGDG and DGDG containing it were not abundant in brown-pigmented raphidophytes which are hypothesized to have a non-green algal plastid ancestry. In the current study we were interested in performing a similar comparison on betaine lipids, a different class of fatty acid-containing lipids that play a structural role similar to phospholipids in many algae and lower plants. We have observed in brown- and green-pigmented raphidophytes that two betaine lipids, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), diaclyglycerylhydroxymethyl-N,N,N-trimethyl-β-alanine (DGTA), are present. Unlike prior observations on the MGDG and DGDG composition of raphidophytes, brown-pigmented raphidophytes were found to produce more forms of DGTS and DGTA, generally with more variants of polyunsaturated C18 fatty acids, than G. semen, thus identifying another way in which to compare algae of a different plastid ancestry.