No abstract

ABSTRACIA comparison was made of epicuticular lipid accumulation on leaves of Lycopersicon pennelii and Lycopersicon esculentum Mill. cv VF36 from 5 to 16 weeks of age. Epicuticular lipids were a small fraction of the leaf dry weight (0.16%) of 5-week-old 'VF36', and increased to only 0.96% of the leaf dry weight after an additional 12 weeks of growth. In contrast, leaves from 5-week-old and 17-week-old L. penneliji plants had, respectively, 0.94% and 19.9% of their total dry weight in epicuticular lipid. Lipid accumulation was not affected by drought stress. Leaf position appears to influence the amount of lipid on the leaf surface. A glycolipid appears to be exuded from the terminal cell of glandular trichomes found on the leaves, stems, peduncles, calyxes, and fruits of L. pennellii.

No abstract

Diacylgalactosylglycerol synthesis was a prerequisite for the incorporation of [1-14C]-acetate into linoleate and alpha-linolenate of isolated spinach (Spinacia oleracea) chloroplasts. Oleate at position 1 of diacylgalactosylglycerol was desaturated to linoleate and alpha-linolenate both in the light and in the dark. Some desaturation of palmitate was also observed after prolonged incubations.

UDP-galactose-'4C, uniformly labeled in the galactose moiety, and UDP-glucose-l4C, uniformly labeled in the glucose moiety, were purchased from New England Nuclear. UDP-galactose-'2C was purchased from Calbiochem. UDP-glucose-12C was purchased from Pabst. Silica Gel G was obtained from Brinkman and silicic acid (Bio-Sil A, 100-200 mesh) was obtained from Calbiochem.Steryl glucosides have been known to exist in plants for some time (21), but the existence of acylated steryl glucosides has been recognized only recently (15). The acylated steryl glucosides have since been studied by Kiribuchi et al. (13,14), and. some aspects of their biosynthesis have been described by Hou et al. (10,11) and Kauss (12). Eichenberger and Menke (5) have made a study of the distribution of free sterols, steryl glycosides, and steryl esters in the subcellular fractions of leaves. They discovered that although half of the leaf lipid was localized in the chloroplast, only one quarter of the total leaf sterol was found in this subcellular organelle. The sugars found in the steryl glycosides were glucose and mannose, and the fatty acid found in the steryl esters was palmitic acid (5). No further information appears to be available concerning the subcellular distribution, and no physiological function has been ascribed to the free sterols and sterol derivatives in plants.In an earlier investigation on the biosynthesis of galactolipids in plants (20) METHODSPreparation of Pea Root Mitochondrial Fraction. Pea seeds were soaked for 16 hr in water before being planted in trays of wet vermiculite. Germination and growth took place in darkness for 5 to 6 days, and the trays were then transferred to light (14 hr of illumination per day). The plants were normally harvested 10 days after germination. The roots were taken and washed with distilled water and then cut -into small pieces. The roots (e.g., 30 g) were ground with mortar and pestle in cold 0.5 M sucrose which was 0.01 M with respect to phosphate buffer, pH 7.4 (e.g., 30 ml). The homogenate was filtered through cheesecloth and then centrifuged at 1,OOOg for 2 min. The pellet was discarded and the supematant centrifuged at 18,000g for 15 min. The pellet was resuspended in the sucrose-phosphate solution used for homogenization and the pellet was centrifuged down again at 18,000g. This washed pellet was resuspended in 0.01 M tris-HCl buffer, pH 7.4 (e.g., 6 ml), with the aid of a glass Potter-Elvehjem homogenizer.Preparation of Spinach Chloroplast Fraction. Spinach was taken from the greenhouse, and the leaves were washed with distilled water. Petioles and midribs were removed, and the remainder of the leaves (e.g., 30 g) were ground with a mortar and pestle in cold 0.5 M sucrose, 0.01 M with respect to phosphate buffer, pH 7.4 (e.g., 30 ml). The homogenate was filtered through four layers of cheesecloth, and this filtrate was centrifuged at 200g for 2 min. The pellet was discarded, and the supernatant was centrifuged at lOOOg for 7 min. The supernatant was carefully removed, and the pellet ...

Isolated intact pea chloroplasts synthesized phosphatidyiglycerol from either I'4Clacetate or j'Clglycerol 3-phosphate. Both time-course and pulse-chase labeling studies demonstrated a precursor-product relationship between newly synthesized phosphatidic acid and newly synthesized phosphatidylglycerol.The synthesis both of CDP-diacylglycerol from exogenous phosphatidic acid and CTIP, and of phosphatidylglycerol from exogenous CDPdiacyiglycerol and glycerol 3-phosphate, could be assayed in fractions obtained from disrupted chloroplasts. Moreover, the enzymes catalyzing these reactions were localized in the inner envelope membrane. Exoge- Purification and Fractionation of Chloroplasts. Intact chloroplasts were obtained from homogenates of 14-to 17-d-old pea seedlings (Pisum sativum var Laxton's Progress No. 9) by differential centrifugation followed by Percoll density gradient centrifugation as described (8), with the following exceptions: 1. the pH of the buffer was adjusted with KOH instead of NaOH; 2. the centrifugation speeds were increased and the times decreased, as modified from the protocol described by Heinz and Roughan (17) to: (a) first sedimentation, 3300g, 90 s; (b) Percoll gradient sedimentation, 13,000g, 5 min; (c) dilution and recovery, and wash sedimentations, 3300g, 90 and 75 s, respectively. Those chloroplasts used directly for lipid synthesizing assays were resuspended in 0.3 M sorbitol in 33.4 mM Tricine-NaOH (pH 7.9).Those chloroplasts which were fractionated were suspended in 0.6 M sucrose (2 mg Chl/ml), and broken by slow freezing (-20°C, about 45 min) and thawing (22-24C, about 30 min) (8). The suspension was diluted with buffer to 0.36 M sucrose, and 5 ml were pipetted over the following sucrose step-density gradients: 1.3 M, 2 ml; 1.2 M, 1 ml; 1.1 M, 4 ml; 0.5 M, 5 ml (as modified from Joyard and Douce [ 18]). The gradients were then centrifuged at 1 16,000gma for 90 min. The soluble stromal components remained within the 0.36 M layer, the envelopes sedimented to the 0.5/1.1 M interface, while the thylakoids sedimented to the 1.3 M layer. A small green pellet, which accounted for 12 to 40% of the total Chl, was assumed to be unbroken chloroplasts. The envelope membranes were collected with a Pasteur pipette, diluted 4-to 5-fold with buffer, and collected by centrifugation (90,000g,,,. 60 min); they were then resuspended in either buffer only or 0.2 M sucrose (usually to about 0.5-1 mg protein/ml). All

No abstract

No abstract