Polar glycerolipids of Chlamydomonas moewusii

The fatty acid and polar lipid compositions of the unicellular green alga C hlamydomonas moewusii were characterized. Since this organism is an importa nt plant model for phospholipid-based signal transduction, interest was foc used on the lipids phosphatidic acid, phosphatidylinositolphosphate and pho sphatidylinositolbisphosphate. A phosphatidylinositol:phosphatidylinositolp hosphate:phosphatidylinositolbisphosphate of 100:1.7:1.3 was found. The pol yphosphoinositides accounted for 0.8 mol% of the total phospholipids and th eir fatty acid compositions were similar to that of phosphatidylinositol ex cept for the enrichment of linolenic acid in phosphatidylinositol phosphate . Phosphatidic acid accounted for 0.67 mol% of the phospholipids. Major str uctural glycerolipids were monogalactosyldiacylglycerol (35 mol%), digalact osyldiacylglycerol (15 mol%), sulfoquinovosyldiacylglycerol (10 mol%), diac ylglyceryltrimethylhomoserine (16 mol%), phosphatidylglycerol (9 mol%), pho sphatidylethanolamine (8 mol%) and phosphatidylinositol (6 mol%). Relative changes in the total fatty acid compositions found during growth on nutrien t-limited medium reflected mainly alterations in the compositions of the ch loroplast lipids phosphatidylglycerol and monogalactosyldiacylglycerol. [P- 32]Pi-incorporation studies revealed that it took 6 days before the amount of label in the major phospholipids was proportional to their abundance. (C ) 2000 Elsevier Science Ltd. All rights reserved.