Changes in galactolipid composition of the cold freshwater dinoflagellate Borghiella dodgei in response to temperature

The freshwater dinoflagellate Borghiella dodgei is adapted to cold temperatures. We investigated the effects of small temperature changes on its galactolipid composition, choosing 3 and 7°C as deviations from its optimal growth temperature (5°C). The galactolipid profile, important for maintenance of membrane fluidity, was determined by liquid chromatography–mass spectrometry and the influence of temperature on galactolipids was investigated by one-way ANOVA. We found 24 different galactolipid species, including novel tri-galactosyldiacylglycerols (TGDGs). The overall amount of mono- (MGDG), di- (DGDG) and tri- (TGDG) galactosyldiacylglycerols remained stable while single galactolipids varied with temperature. Few changes were found from 3 to 5°C, instead 11 galactolipid species changed from 5 to 7°C. Concomitantly with the unsaturation index of MGDGs, the more unsaturated galactolipids decreased at higher temperature, and the less abundant and less unsaturated galactolipids in each lipid class accumulated. Changes in the galactolipid profile of Borghiella underlined its cold-stenothermal nature: it can adapt to relatively ‘higher’ temperatures by reducing the synthesis of the more unsaturated MGDGs, DGDGs and TGDGs, but remains restricted by its lower growth rate. Based on our results, we predict that with climate change the galactolipid profile of cold-stenothermal algae will change with important repercussions on their consumers.