Isolation of chloroplasts from marine microalgae Isochrysis galbana Parke suitable for organelle lipid composition analysis

Abstract

Background: Marine microalgae, Isochrysis galbana Parke, is an important diet microalgal species with high nutritional value. Different from other unicellular microalgae, its cell contains two chloroplasts which are the major sites for lipid synthesis. Results: Here, we optimized a chloroplast isolation approach suitable for I. galbana Parke, and evaluated the purity and integrity of the isolated chloroplasts by microscopic observations and biochemical assays. The chloroplast lipids were sequenced by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Glycolipids were the main chloroplast lipids, and DGDG, MGDG, and SQDG were the most abundant glyceroglycolipids. DGMG and SQMG were not observed among the chloroplast lipids. In addition, DG was the most abundant neutral lipid. A part of fatty acyl R1/R2 with MGMGs, DGDGs, MGDGs, SQDGs, PEs, and PCs were not found in chloroplasts. The fatty acid proportion of chloroplast lipids were increased, decreased, or remained unchanged compared with the whole-cell. Conclusions: This newly developed isolation approach was a simple and reliable method to isolate chloroplasts with high integrity and purity. Collectively, our findings show that such an isolation approach may be used in studies on many different aspects of chloroplast biology, and offers a useful reference for isolation of chloroplast from other marine microalgae.

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea

“…Nevertheless, one may speculate that there are two separated PKS pathways, one for the 22:6n-3 and one for the 18:5n-3, as these two PUFA are localized in different cell compartments. The 18:5n-3 is generally associated with chloroplastic glycolipids, while the 22:6n-3 is predominant in the other cellular compartments [51][52][53]. The 18:5n-3 was also described as an intermediate of 22:6n-3 synthesis by PKS pathway [4].…”