Diacylglyceryl-N,N,N-trimethylhomoserine-dependent lipid remodeling in a green alga, Chlorella kessleri

Membrane lipid remodeling contributes to the environmental acclimation of plants. In the green lineage, a betaine lipid, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), is included exclusively among green algae and nonflowering plants. Here, we show that the green alga Chlorella kessleri synthesizes DGTS under phosphorus-deficient conditions through the eukaryotic pathway via the ER. Simultaneously, phosphatidylcholine and phosphatidylethanolamine, which are similar to DGTS in their zwitterionic properties, are almost completely degraded to release 18.1% cellular phosphorus, and to provide diacylglycerol moieties for a part of DGTS synthesis. This lipid remodeling system that substitutes DGTS for extrachloroplast phospholipids to lower the P-quota operates through the expression induction of the BTA1 gene. Investigation of this lipid remodeling system is necessary in a wide range of lower green plants for a comprehensive understanding of their phosphorus deficiency acclimation strategies.

Diacylglyceryl-N,N,N-trimethylhomoserine-dependent Lipid Remodeling in a Green Alga, Chlorella Kessleri

Membrane lipid remodeling contributes to environmental 19 acclimation of plants. In a green lineage, a betaine lipid, diacylglyceryl-N,N,N-trimethylhomoserine (DGTS), is included exclusively among green algae and non-flowering plants. Here we show that, a green alga, Chlorella kessleri, reported to exceptionally possess no DGTS, synthesizes it specifically under phosphorus-deficiency conditions through the eukaryotic pathway via the ER. Simultaneously, phosphatidylcholine and phosphatidylethanolamine, which are similar to DGTS in its zwitterionic property, are almost completely degraded to release 18.1% cellular phosphorus, and to provide its diacylglycerol moieties for a part of DGTS synthesis. Above lipid remodeling system that substitutes DGTS for extrachloroplast phospholipids to lower the P-quota operates through expression induction of the gene for BTA1 that is functionally identified as responsible for DGTS synthesis, and those for0 phospholipid breakdown. Investigation of this lipid remodeling is necessary in a widerange of lower green plants for a comprehensive understanding of their phosphorus deficiency acclimation strategies.

Lipidomics and Anti-Inflammation Activity of Brown Algae, Lobophora sp., in Vietnam

Lobophora sp., belonging to brown macro algae phylum, is found in coral reefs. In this study, the fatty acid composition, lipid classes, polar lipid molecular forms, and bioactivities of this algae have been determined. It follows that five classes including polar lipid (Pol), sterol (ST), free fatty acids (FFA), triacylglycerol (TAG), and hydrocarbon and wax (HW), 23 fatty acids containing 5 PUFAs (ALA, GLA, AA, EPA, and DHA) and 157 molecular types of polar lipid group containing 48 phospholipid molecular forms belonging to 4 subclasses (PI (11), PC (14), PG (22), PA (1)), 45 glycolipid molecular forms classified into 3 subclasses of MGDG (8), DGDG (1), SQDG (36), and 64 betaine lipid molecular forms belonging to 2 subclasses (DGTA (37), DGTS (27)) have been identified for the first time from this algae. Furthermore, both polar lipid (PL) and unpolar lipid (UPL) show the NO inhibition activities with values of IC50 ranging from 52.10 to 66.21 µg/mL. Thus, lipid of this brown algae could promise to be a potential source for application in food, cosmetic, and pharmaceutic industry.

Phosphate starvation induces replacement of phospholipids with the betaine lipid diacylglycerol-N,N,N-trimethylhomoserine in the human fungal pathogen Candida albicans

We have previously demonstrated that phosphate starvation induces replacement of phosphatidylcholine with the betaine lipid diacylglyceryl-N,N,N-trimethylhomoserine (DGTS) in fungi. In Neurospora crassa, the BTA1 gene encodes the betaine lipid synthase, which is necessary and sufficient for DGTS synthesis. BTA1 expression and DGTS accumulation are part of the fungal phosphorus (Pi) deprivation (PHO) regulon, mediated by the NUC-1/Pho4p transcription factor. We now demonstrate that the human pathogen Candida albicans encodes a BTA1 ortholog (CaBTA1), which is activated during Pi scarcity. The CaBTA1 gene is also induced under certain biofilm-promoting conditions independent of Pi starvation. RNA-seq and qRT-PCR showed a significant increase in CaBTA1 expression in response to Pi limitation. Thin-layer chromatography and LC-ESI-MS/MS confirmed the replacement of PC with DGTS in wild-type under low Pi and showed the absence of DGTS in the bta1ΔΔ mutant.Pi limitation in the gut of critically ill patients also triggers the switching of C. albicans into an invasive filamentous form. To assess the role of BTA1 and DGTS in the pathogenicity of C. albicans in vitro, we compared the growth and morphology of bta1ΔΔ and wild type in hyphaeinducing media and observed defects in biofilm formation and invasive growth in the bta1ΔΔ mutant. This observation is complemented by RNA-seq data demonstrating that Pi starvation in planktonic C. albicans cells induces the expression of virulence-associated cell surface proteins. Taken together, these results show novel functional interactions between lipid metabolism and remodeling, biofilm formation, and the phosphate starvation response of C. albicans.

Phosphate Starvation in Fungi Induces the Replacement of Phosphatidylcholine with the Phosphorus-Free Betaine Lipid Diacylglyceryl-N,N,N-Trimethylhomoserine

ABSTRACTDiacylglyceryl-N,N,N-trimethylhomoserine (DGTS) is a phosphorus-free betaine-lipid analog of phosphatidylcholine (PtdCho) synthesized by many soil bacteria, algae, and nonvascular plants. Synthesis of DGTS and other phosphorus-free lipids in bacteria occurs in response to phosphorus (P) deprivation and results in the replacement of phospholipids by nonphosphorous lipids. The genes encoding DGTS biosynthetic enzymes have previously been identified and characterized in bacteria and the algaChlamydomonas reinhardtii. We now report that many fungal genomes, including those of plant and animal pathogens, encode the enzymatic machinery for DGTS biosynthesis, and that fungi synthesize DGTS during P limitation. This finding demonstrates that replacement of phospholipids by nonphosphorous lipids is a strategy used in divergent eukaryotic lineages for the conservation of P under P-limiting conditions. Mutants ofNeurospora crassawere used to show that DGTS synthase encoded by theBTA1gene is solely responsible for DGTS biosynthesis and is under the control of the fungal phosphorus deprivation regulon, mediated by the NUC-1/Pho4p transcription factor. Furthermore, we describe the rational reengineering of lipid metabolism in the yeastSaccharomyces cerevisiae, such that PtdCho is completely replaced by DGTS, and demonstrate that essential processes of membrane biogenesis and organelle assembly are functional and support growth in the engineered strain.