Hormone-Controlled Synthesis of Endoplasmic Reticulum in Barley Aleurone Cells

Evins, Warren H.; Varner, Joseph E.

doi:10.1073/pnas.68.7.1631

Cited by 85 publications

(30 citation statements)

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“…Many GA3-induced changes in barley aleurone cells can be blocked by abscisic acid (ABA), including the synthesis of aamylase (6), the formation ofpolysomes (1 1), and the stimulation of phospholipid synthesis (10,21,23 effective and consistent antagonist of GA3-induced events, its effect on the shift in total lipase activity from the l0,OOOg pellet to the lipid body fraction was tested. As shown in Table IV, the relative increase in lipase activity in lipid body fractions is also sensitive to ABA treatment.…”

Section: Resultsmentioning

confidence: 99%

“…Within 2 h after the cells are exposed to GA3, the in vitro activities oftwo enzymes involved in phospholipid synthesis, phosphorylcholine-cytidyl transferase (EC 2.7.7.15) and phosphorylcholineglyceride transferase (EC 2.7.8.2), increase (1,21). Within 4 h, increased incorporation of radiolabeled choline into a microsomal fraction (10) and of radiolabeled orthophosphate into phospholipids (23) is observed. On the other hand, radiolabeled acetate and glycerol are not incorporated into phospholipids to any great extent in aleurone cells (14, 23,32,35 are predominantly used for new phospholipid synthesis (35).…”

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confidence: 99%

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Does Gibberellic Acid Induce the Transfer of Lipase from Protein Bodies to Lipid Bodies in Barley Aleurone Cells?

Fernandez¹,

Staehelin²

1987

Plant Physiol.

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We have examined the effect of gibberellic acid (GA3) on the distribution of the enzyme responsible for mobilizig storage triacyglycerol in aleurone cells of HordeEm Pulgare L. cv Himalaya. Using cellular fractionation techniques, we find that, in cells that have not been exposed to hormone, neutral lipase activity is principally associated with a pellet containing the membranes of protein bodies. If the cells are exposed to GA3 for at least 1 hour, the majority of the lipase activity becomes associated with the lipid body fraction. The nature of the in vivo association between lipid bodies and protein bodies was examined using ultrarapid freezing followed by freeze-fracture electron microscopy. Our Few investigators have looked at the processes that supply the phospholipid precursors and energy in aleurone layers, i.e. the reactions involved in the hydrolysis of triacylglycerols. Enzymes involved in the release of energy from fatty acids via the glyoxylate cycle appear within 1 to 2 d ofgermination in whole wheat seeds and can be induced by GA3 in embryo-less seeds (9). Lipases that are involved in triacylglycerol hydrolysis also appear in whole wheat seeds after 1 d of germination but cannot be induced by GA3 in embryo-less seeds (30). Jelsema et al. (20) have shown, however, that isolated wheat aleurone layers that have not been exposed to GA3 do contain acid lipase activity. In addition, their observations present an interesting enigma. Although triacylglycerols, the apparent substrate, are found within lipid bodies, the acid lipase activity is located principally in a pellet containing protein bodies. When the cells are exposed to GA3, the lipase activity disappears from the pellet (20).We have reexamined the distribution of lipase and GA3-induced changes in that distribution more closely using cellular fractionation techniques and electron microscopy. Our biochemical data indicate that lipase is associated with protein bodies as well as with lipid bodies. The distribution oflipase between these two organelles appears to be controlled by GA3. Since our structural data indicate that lipid bodies can bind to the surface ofprotein bodies and that the monolayer that surrounds the lipid body becomes continuous with the outer leaflet of the bilayer that surrounds the protein body, we propose that lipase may be transferred between the two organelles by lateral diffusion. A preliminary report of our biochemical findings appeared in Fernandez and Staehelin (13).MATERIALS AND METHODS Plant Materials. Aleurone layers of Hordeum vulgare L. cv Himalaya (1979 harvest, Washington State University, Pullman, WA) were prepared from surface-sterilized, embryo-less half seeds (7) imbibed for 4 d in 50 mm L-arginine (18). Layers were incubated on a rotary shaker at 26°C in 2 mm sodium-acetate buffer (pH 4.8) containing 20 mM CaCl2, 7.5 mg/ml chloramphenicol, and either 10 uM GA3 (Sigma Chemical Co.) or H20.Isolation of lipid bodies. Lipid bodies were isolated using a modification ofa procedure developed originally fo...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Does Gibberellic Acid Induce the Transfer of Lipase from Protein Bodies to Lipid Bodies in Barley Aleurone Cells?

Fernandez¹,

Staehelin²

1987

Plant Physiol.

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“…In studying the biochemical sequence of events during this lag period, we found an increase in polyribosome formation and an increased synthesis of ribosomes (6) and endoplasmic reticular membranes (7). These effects begin to occur within 2 to 4 hr after hormone application (6,7).…”

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confidence: 99%

“…These effects begin to occur within 2 to 4 hr after hormone application (6,7). Using the distinctive tryptophan-tyrosine ratio of a-amylase and of some of the other GA-induced proteins as a chemical identification tag, we showed that the polysomes responsible for the new enzyme synthesis are those polysomes produced in the presence of the hormone (6).…”

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Hormonal Control of Polyribosome Formation in Barley Aleurone Layers

Evins

Varner

1972

Plant Physiol.

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The addition of abscisic acid to barley (Hordeurn vulgare L. cv. Himalaya) aleurone layers at the same time as gibberellic acid completely prevents the gibberellin-induced increases in the percentage of polysomes, the formation of polyribosomes, and the synthesis of a-amylase, even when the molar concentration of gibberellic acid is four times greater than the concen- Gibberellic acid and abscisic acid affect both the conversion of monosomes to polysomes and the synthesis of new ribosomes. The gibberellin-stimulated increases in the number of ribosomes and the percentage of polysomes are probably a prerequisite for the hormone induction of enzyme synthesis.

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“…There is, however, a prominent lag period (8-10 hr) that precedes the onset of GA-mediated hydrolase synthesis and secretion (4). Early changes elicited by GA during this lag period are the proliferation and stacking of rough endoplasmic reticulum (RER) (5), enhancement of polysome formation (6), and the incorporation of ['4C]choline into a lipid-soluble component of the polysome fraction, presumably RER (6,7). A possible means by which GA may influence the biosynthesis of RER is through the enhancement of the activities of enzymes involved in phospholipid biosynthesis.…”

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Hormonal Control of Lecithin Synthesis in Barley Aleurone Cells: Regulation of the CDP-Choline Pathway by Gibberellin

Johnson

Kende

1971

Proc. Natl. Acad. Sci. U.S.A.

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The enzymes of the cytidine diphosphatecholine pathway, which is involved in lecithin biosynthesis, are present in imbibed barley aleurone cells. The first enzyme, choline kinase (EC 2.7.1.32), is found in the soluble protein fraction. Its activity is not affected by prior treatment of aleurone layers with gibberellin. The second and third enzymes of the pathway, phosphorylcholine-cytidyl (EC 2.7.7.15) and phosphorylcholineglyceride (EC 2.7.8.2) transferases, are associated with the particulate fractions. Their activities are greatly increased by gibberellin treatment during the lag phase (0-8 hr) of gibberellin-effected a-amylase synthesis. The hormonal effects are evident two hours after gibberellin treatment. Inhibitors that block gibberellin-effected a-amylase formation also inhibit the stimulation of these membrane-bound enzymes by the hormone.In barley aleurone cells, the synthesis and secretion of several hydrolytic enzymes are controlled by gibberellin (GA) (1). At least two of the hydrolases are synthesized de novo as a result of GA action (2, 3). There is, however, a prominent lag period (8-10 hr) that precedes the onset of GA-mediated hydrolase synthesis and secretion (4). Early changes elicited by GA during this lag period are the proliferation and stacking of rough endoplasmic reticulum (RER) (5), enhancement of polysome formation (6), and the incorporation of ['4C]choline into a lipid-soluble component of the polysome fraction, presumably RER (6, 7). A possible means by which GA may influence the biosynthesis of RER is through the enhancement of the activities of enzymes involved in phospholipid biosynthesis. We have investigated this possibility and now report the presence of, and the effect of GA on, enzyme activities of the CDP-choline pathway in barley aleurone cells. MATERIALS AND METHODSSeed Preparation and Treatment. Half-seeds of barley (Hordeum vulgare L., cv. Himalaya) were prepared as described by Chrispeels and Varner (8) and allowed to imbibe at 250C for 4 days. Either half-seeds or aleurone layers (50 per treatment) were placed in 250-ml Erlenmeyer flasks containing 10 ml of 2 mM Na acetate buffer (pH 4.8), with or without 1

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Hormone-Controlled Synthesis of Endoplasmic Reticulum in Barley Aleurone Cells

Cited by 85 publications

References 20 publications

Does Gibberellic Acid Induce the Transfer of Lipase from Protein Bodies to Lipid Bodies in Barley Aleurone Cells?

Does Gibberellic Acid Induce the Transfer of Lipase from Protein Bodies to Lipid Bodies in Barley Aleurone Cells?

Hormonal Control of Polyribosome Formation in Barley Aleurone Layers

Hormonal Control of Lecithin Synthesis in Barley Aleurone Cells: Regulation of the CDP-Choline Pathway by Gibberellin

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