Aspects of phosphorus physiology associated with phosphate-induced polar lipid remodelling in marine microalgae.

Marine microalgae exhibit a diversified phosphorus physiology and have also been recently found to show high inter-taxa variability in their phosphate induced-polar lipids' remodelling. Identification of phosphorus physiology aspects that are more related to lipid remodelling can contribute to better understanding of such intricate phytoplankton lipid metabolism. Therefore, some aspects of phosphorus physiology related to its uptake, storage and use were evaluated in a taxonomically diversified group of nine marine microalgae that was arranged into three subgroups, each of them including species showing similar polar lipid responses to phosphate. Luxury phosphate uptake (PU) was the physiological aspect best associated to microalgal polar lipid metabolism as it was maximal in species (Picochlorum atomus, Tetraselmis suecica and Nannochloropsis gaditana) that were able to counterbalance between phospholipids (PL) and betaine lipids (BL). Cryptophytes (Rhodomonas baltica, Chroomonas placoidea), characterized by their constitutive BL and flexible PL contents in response to phosphate, had almost no luxury PU and showed higher phosphorus cell quota (QP) under phosphate deprivation. Haptophyes (Isochrysis galbana, Diacronema vlkianum), with constitutive BL contents and permanently minimal PL contents, showed the lowest QP when deprived of phosphate while their luxury PU was below that for green microalgae. Induction of alkaline phosphatase activity following phosphate depletion was maximal in diatoms (Phaeodactylum tricornutum, Chaetoceros gracilis) and I. galbana but it was unrelated to lipid remodelling. Despite strong influence of taxonomy, polar lipid remodelling accounted for 38.8% of total variation when microalgae were ordinated using their physiological responses to phosphorus as descriptive variables.