Membrane Transformations in Aging Potato Tuber Slices

Castelfranco, Paul A.; Tang, Wenjing; Bolar, Marlin L.

doi:10.1104/pp.48.6.795

Cited by 19 publications

(4 citation statements)

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“…The effectiveness of choline as a precursor of membrane 'This work was supported by National Science Foundation Grant GB 24961. 61 constituents has already been demonstrated in several plant systems (3,7,14).…”

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confidence: 83%

“…After 6 hr when the available choline-4C had been exhausted, the 14C content of the glyoxysomes (roughly 10% of the total incorporated) showed a marked decline. The closed circles show the response when, as indicated by the arrows in Figure 3, a 125-fold excess of unlabeled choline was added 1 hr after the application of choline-"C. Incorporation into mitochondria and glyoxysomes continued for the subsequent 3 hr, but at a diminishing rate and much more slowly than in the controls not receiving the "chase" of unlabeled choline. After 6 hr the 14C content of the mitochondria declined quite slowly, while that of the glyoxysomes showed a steeper decline.…”

Section: Methodsmentioning

confidence: 99%

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The Origin and Turnover of Organelle Membranes in Castor Bean Endosperm

Kagawa

Lord²,

Beevers³

1973

Plant Physiol.

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The origin and turnover of organelle membranes in castor bean (Ricinus communis L. var. Hale) endosperm was examined using choline-"C as a phospholipid precursor. On sucrose gradients three major particulate fractions were separated; a light membranous fraction (density 1.11-1.13 gram per cm3), the mitochondria (1.18 gram per cm3), and the glyoxysomes (1.24 gram per cm'). Choline-14C was readily incorporated into lecithin in all three particulate fractions, but the light membranous fraction became labeled first. Incorporation continued into all three fractions for 6 hours, at which time the available choline-"4C had been completely used. Subsequently, 14C was lost from the three components at distinctly different rates. When an excess of unlabeled choline was added after 1 hour (pulse-chase experiment), incorporation of choline-14C into glyoxysomes and mitochondria continued for three hours, but at a diminishing rate. This was followed by a period in which the 14C content of the mitochondria declined at a rate expected, if the half life of lecithin in the membrane were about 50 hours and that of the glyoxysomes 10 hours. These values are close to those calculated from the experiments in which no chase was used. The labeling in the light membrane fraction behaved differently from that of the mitochondria and glyoxysomes following the chase of unlabeled choline. Incorporation continued for only 1 additional hour, and then the "C content declined sharply in the subsequent 4 hours. The early kinetics and subsequent interrelationships are those expected if the lecithin in the membranes of mitochondria and glyoxysomes originates in components of the light membrane fraction.A striking increase in organelles housing enzymes of the gluconeogenic pathway occurs during the onset of fat breakdown in seedlings (4, 8, 11-13, 17, 20, 21). In the endosperm of castor bean seeds germinating at 30 C, the numbers of glyoxysomes and mitochondria increase during the first 5 days and decline when fat utilization is complete (8). The mechanism of biogenesis, maintenance, and destruction of these organelles is of interest. One approach is to examine the turnover of proteins and individual enzymes (9, 16). Another consideration is the behavior of the membranes surrounding the organelles. The effectiveness of choline as a precursor of membrane 'This work was supported by National Science Foundation Grant GB 24961. 61 constituents has already been demonstrated in several plant systems (3, 7, 14).Here we examine the origin and turnover of organelle membranes as revealed by the incorporation of choline-"C into lecithin. MATERIALS AND METHODSPlant Material. Seeds of castor bean (Ricinus communis L. var. Hale) were soaked in running water for 1 day and grown in moist vermiculite in darkness at 30 C. Seedlings of particular ages were carefully chosen for uniformity, and the seeds were detached at the hypocotyl. The testae were removed, and the seeds were surface sterilized by immersion for 10 sec in 30% (v/v) Clorox solution and 30...

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confidence: 83%

Section: Methodsmentioning

confidence: 99%

The Origin and Turnover of Organelle Membranes in Castor Bean Endosperm

Kagawa

Lord²,

Beevers³

1973

Plant Physiol.

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“…When isolated mitochondria are separated centrifugally in a density gradient, mitochondria from aged slices form a sharper, i.e. more homogeneous, band than mitochondria from fresh slices (8). In this context, it has been discovered that more than 30% of the phospho-and galactolipid of potato slices is degraded in 15 to 30 min at 0 C following cutting with the bulk of it resynthesized in the next 24 hr (40).…”

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confidence: 99%

“…On the other hand, a marked increase is observed in the capacity for acetate incorporation into fatty acids (43), and choline incorporation into phospholipids (3,5,39). In this connection, labeled choline is distributed among the various cell membranes, including mitochondrial membranes (8).…”

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confidence: 99%