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D R Janero

Publications and source records attributed to D R Janero.

59 records · Page 4Linked to original sources
PubMed1982

Isolation and characterization of an ether-linked homoserine lipid from the thylakoid membrane of Chlamydomonas reinhardtii 137+.

A polar diacylglycerolipid isolated from the phototrophic green alga Chlamydomonas reinhardtii 137+ (wild-type) displays chromatographic and chemical identity with the either-linked homoserine lipid 1(3),2-diacylglyceryl-(3)-O-4'(N,N,N-trimethyl)homoserine (DGTS) of the golden alga Ochromonas danica. Subcellularly, DGTS is a constituent of a fraction of thylakoid membranes purified from Chlamydomonas whole-cell homogenates. The proportion of DGTS in the photosynthetic lamellae is approximately 40% of the total found in the alga. Cellular and thylakoid-membrane DGTS both have an unsaturated:saturated ratio of about 1.8 and contain predominantly hexadecanoic and octadecanoic fatty acids. Quantitatively, the fatty acid complement of thylakoid DGTS is distinct from the cellular DGTS fatty acid profile. The results provide the first demonstrations that DGTS is a bona fide membrane lipid and, specifically, that ether-linked homoserine lipid is a component of the thylakoid membrane of a phototrophic green-plant cell.

Cell Membrane↗
PubMed1981

Thylakoid membrane biogenesis in Chlamydomonas reinhardtii 137+: cell cycle variations in the synthesis and assembly of polar glycerolipid.

The synthesis and assembly of thylakoid membrane polar glycerolipid (glycolipid, phospholipid, and ether lipid) have been monitored in synchronous cultures of the green alga Chlamydomonas reinhardtii 137+. A "pulse" protocol using radioactive acetate as the lipogenic precursor was devised to allow assessment of both processes during the 24-h (12-h light/12-h dark) vegetative cell cycle. Under these conditions, acetate incorporation into each chromatographically resolved lipid at the cellular level reliably reflects lipid synthesis, and the appearance of radiolabeled lipid in purified photosynthetic membrane is indicative of the lipid assembly attendant to thylakoid biogenesis. Our results demonstrate that polar glycerolipid is synthesized by the alga and is assembled into its thylakoid membrane continuously, but differentially, with respect to cell cycle time. Synthesis and assembly are most rapid during the photoperiod (mid-to-late G1), reach maximum rates at mid-photoperiod, and are comparatively negligible in the dark (S, M, and early-to-mid G1). The extent to which synthesis and assembly vary within this general kinetic pattern, though, is characteristic of each thylakoid lipid, suggesting that the processes take place in a multistep manner with some temporal coordination among the different lipid types. Parallelism between the cyclic patterns of polar lipid synthesis at the cellular level and of polar lipid assembly into photosynthetic membrane at the subcellular level indicates that lipid production is not only essential to continuing thylakoid biogenesis but is also the critical determinant of the kinetics of thylakoid lipid assembly.

Acetates↗
PubMed1981

Cellular and thylakoid-membrane glycolipids of Chlamydomonas reinhardtii 137+.

The glycolipids of the green alga Chlamydomonas reinhardtii 137+ have been quantitated in the phototrophically-cultured cell and in its thylakoid membrane. Three lipids, the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the sulfated glycolipid sulfoquinovosyldiacylglycerol (SL), constitute the total glycolipid complement and some 70-80% of the total polar lipid at both levels. About 70% of the alga's sulfolipid, but only about half of its galactolipid, is localized in the thylakoid. The three cellular and thylakoid glycolipids all contain prominent hexadecanoic and octadecanoic fatty acids. Quantitatively, each lipid has a distinctive acyl profile, making SL the most highly saturated and MGDG the least saturated glycolipid. Differences between the fatty acid profiles of each corresponding cellular and thylakoid glycolipid indicate that discrimination of the glycolipid species assembled into photosynthetic membrane takes place during thylakoid membrane biogenesis.

Cell Membrane↗
PubMed1981

Cellular and thylakoid-membrane phospholipids of Chlamydomonas reinhardtii 137+.

The phospholipids of phototrophically-cultured Chlamydomonas reinhardtii 137+ have been quantitated at the cellular and thylakoid membrane levels. The alga contains three major phospholipids, phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC), which together constitute about 14% of the cellular polar lipid complement. PG is the only phospholipid in an analytical fraction of thylakoid membrane isolated from the alga, and represents about 9% of the membrane's total polar lipid. Slightly more than half the cellular PG is localized in the photosynthetic lamellae. Hexadecanoic and octadecanoic fatty acids make up over 70% of the acyl groups esterified to these phospholipids, PG being the most highly unsaturated of the three. Differences in fatty acid profile between cellular and thylakoid PG, as well as the presence of PE and PC in the alga but not in its thylakoid, are indicative of a strict biogenetic regulation of the specific types and species of phospholipid associated with the photosynthetic membrane.

Cell Membrane↗