Occurrence of an acyl-CoA:1-acylglycerophosphorylcholine acyltransferase in plant mitochondria.

In the presence of oleoyl-CoA, purified and intact mitochondria from potato tuber formed phosphatidylcholine from labeled lysophosphatidylcholine. The labeled oleoyl moiety of the acyl-CoA was also incorporated in the absence of exogenous lysolipids, such incorporation being largely increased by the addition of exogenous lysophosphatidylcholine. In the presence of various other lysophospholipids, no synthesis of the corresponding phospholipids was observed, suggesting a high specificity of the acyltransferase towards the acyl acceptor. This enzyme was chiefly located in the outer membrane of mitochondria. These results indicate that any acylglycerophosphorylcholine transferred from the endoplasmic reticulum to mitochondria may be acylated to phosphatidylcholine.

[Comparative analysis of ultrastructure and lipid composition of plastids from sun and shade plants (author's transl)]. / Analyse comparative de l'ultrastructure et de la composition lipidique des chloroplastes de plantes d'ombre et de soleil.

The ultrastructure and lipid composition of chloroplasts, isolated from various shade and sun plants, were compared. Depending on the origin of the plastid, significant differences were observed in the percentage of appressed thylakoids. Accordingly, plastids could be classified into three different types: Type I chloroplasts, from mesophyll cells of sun plants (barley, corn, spinach, bean), display well-developed grana and intergrana thylakoid membranes. Type II chloroplasts, typical of shade plant (Arum), show giant grana stacks with few interconnecting thylakoids. Type III chloroplasts, from bundle sheath cells of leaves from C4-plants (corn), are characterized by an extensive development of stroma thylakoids with only occasional rudimentary grana. The percentages of appressed membranes are in the ranges of 50 to 60%, 80% and 2% for type I, II and III plastids respectively. Striking differences are observed in the fatty acid composition of phosphatidylglycerol molecules. Trans-delta3-hexadecenoic acid is found only in this phospholipid and amounts to 30 to 40%, 50% and less than 8% of total fatty acids in type I, II and III plastids respectively. The comparison of ultrastructural and biochemical data suggests a strong correlation between the amounts of phosphatidylglycerol molecules containing trans-delta3-hexadecenoic acid and the percentages of appressed membranes (grana stacks) within plastid stroma.

Sur l'incorporation de la radioactivite du sn-glycerol-3-phosphate-(14)C dans le monogalactosyldiglyceride des plastes isoles.

Isolated plastids (chloroplasts and etioplasts) that are morphogically intact and free of any contamination from other cell structures can incorporate label from sn-glycerol-3-phosphate-(14)C into monogalactosyldiglyceride.