Alterations of Membrane Lipid Content Correlated With Chloroplast and Mitochondria Development in Euglena gracilis

Abstract

Euglenoids are unique protists that can grow photoautotrophically, photomixotrophically, and heterotrophically. Here we grew Euglena gracilis under these different growth conditions and determined cellular contents of seven membrane lipids and one storage lipid (triacylglycerol), which account for more than 94 mol% of total membrane lipids. We also describe the relationship among chloroplast and mitochondria developments with lipid contents, protein contents, and oxygen evolution/consumption rates. In photoautotrophic growth conditions, E. gracilis cells accumulated chlorophyll, photosynthetic proteins, and glycolipids typical to thylakoid membranes. The same occurred for the cells grown under photomixotrophic conditions with higher respiration rates. In heterotrophic conditions, E. gracilis cells had higher respiration rates compared to cells grown in other conditions with the accumulation of pyruvate: NADP+ oxidoreductase, a mitochondrial protein and phospholipid common in mitochondria. Cells were also observed using a confocal laser scanning microscope and found to show more chlorophyll autofluorescence when grown photoautotrophically and photomixotrophycally, and fluorescence of MitoTracker when grown photomixotrophically and heterotrophically. These results suggest that under illumination, E. gracilis develops functional thylakoid membranes with membrane lipids and proteins for photosynthesis. In the medium with glucose, the cells develop mitochondria with phospholipids and proteins for respiration. Possible application based on lipid analysis for the enhancement of wax ester or alkene synthesis is discussed.

Proteome of the secondary plastid of Euglena gracilis reveals metabolic quirks and colourful history

“…This is probably related to the loss of starch synthesis during the emergence of the euglenophyte secondary plastid and the switch to extraplastidial paramylon (-1,3-glucan) as the main storage compound (Barsanti et al 2001 The E. gracilis plastid is also a site for biosynthesis of fatty acids and glycerolipids. The latter include the major plastid phospholipid phosphatidylglycerol and three glycolipids, monogalactosyl-and digalactosyldiacylglycerol (MGDG and DGDG) and sulfoquinovosyl-diacylglycerol (SQDG), in agreement with biochemical evidence documenting these lipids in the E. longa plastid (Matson et al 1970;Blee and Schantz 1978;Shibata et al 2018). We were able to reconstruct pathways for synthesizing these compounds, albeit with several enzymes missing from the proteome, but predicted by the transcriptome.…”

Influence of long term nitrogen limitation on lipid, protein and pigment production ofEuglena gracilisin photoheterotrophic cultures

“…The most abundant PUFA in all cultures was α-linolenic acid (ALA) and the most abundant LC-PUFAs were arachidonic acid (ARA) and eicosapentaenoic acid (EPA) (Table 3). In addition, E. gracilis is known to produce C16:4 PUFA (Shibata et al, 2018; Tossavainen et al, 2018), but since it was not included in our standards, it was excluded from the analysis. The nutritional status of cultures clearly influenced FA metabolism.…”

Metabolic quirks and the colourful history of the Euglena gracilis secondary plastid

“…The E. gracilis plastid is also a site for biosynthesis of fatty acids and glycerolipids, the latter including the major plastid phospholipid phosphatidylglycerol and three glycolipids, monogalactosyl- New Phytologist and digalactosyl-diacylglycerol (MGDG and DGDG) and sulfoquinovosyl-diacylglycerol (SQDG) (Matson & Meifei 1970;Blee & Schantz, 1978;Shibata et al, 2018). We reconstructed pathways for the synthesis of these compounds, albeit with several enzymes only predicted by the transcriptome.…”