Localization of phytochrome in etioplasts and its regulation
            <i>in vitro</i>
            of gibberellin levels

Evans, Audrey E.; Smith, Harry

doi:10.1073/pnas.73.1.138

Cited by 73 publications

(9 citation statements)

References 13 publications

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“…In contrast to R, cholines inhibited both the lengthening of first leaf and coleoptile. Choline compounds are known inhibitors of the biosynthesis of gibberellins (Deeva 1980) that are mainly responsible for stem lengthening, whereas R via phytochrome influences gibberellin activity in a different manner (Evans and Smith 1976;De Greef and Friderico 1983;Behringer et al 1990). …”

Section: Resultsmentioning

confidence: 98%

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

et al. 2005

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Effects of choline compounds (2-chloroethyltrimethylammonium chloride and 2-ethyltrimethylammonium chloride) as well as red radiation (R) pulse on the dynamics of cytokinin changes, growth and chlorophyll (a + b) accumulation were studied during the growth and greening of etiolated wheat seedlings (Triticum aestivum L., var. Mironovskaya-808). The seedlings were grown for 120 h in the dark and then exposed for 72 h to white light. Pre-treatment of caryopses with cholines and pre-irradiation of etiolated seedlings with R inhibited elongation of both coleoptile and first leaf; but the same factors accelerated these growth responses when seedlings were exposed to white light. Chlorophyll (Chl) accumulation and the first leaf appearance from coleoptile were accelerated by the pre-treatments as well. Far-red radiation (FR) reversed all effects of R but choline pre-treatment eliminated partly R/FR photoreversibility. Two compounds with high cytokinin activity (tested on a fresh weight basis by the bioassay with Amaranthus caudatus L.) were found in shoots and first leaves. One of them had R f , UV absorbance spectrum and the biological activity similar to N 6 -(D 2 -isopentenyl)adenosine. Another cytokinin-like substance was not identified with the used standards. Stimulation of greening by R pulse and cholines was accompanied with accelerated accumulation of both cytokinin-like substances. We conclude that the influence of R and cholines on the concentration of substances with cytokinin activities detected in the leaves might be involved in the stimulation of Chl accumulation.

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Section: Resultsmentioning

confidence: 98%

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

et al. 2005

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“…In addition, two laboratories have presented evidence suggesting that GAs may be synthesized or released by plastids upon their illumination by red light (5,8).…”

Section: Introductionmentioning

confidence: 99%

Uptake and Subcellular Compartmentation of Gibberellin A₁ Applied to Leaves of Barley and Cowpea

Ohlrogge

Garcı́a-Martı́nez²,

Adams³

et al. 1980

Plant Physiol.

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The uptake and subcellular accumulation of gibberellin A1 (GA1) by leaves and protoplasts of barley (cv. Numar) and cowpea (cv. Blackeye pea No. 5) were investigated.Uptake of GA1 by cowpea leaves is optimal at pH 5.8 and occurs by a saturable, probably carrier-mediated process having a half-maximal velocity at 10 to 20 micromolar. Uptake by both barley and cowpea leaves is inhibited by low temperature (+4 C) and the metabolic inhibitors 2,4-dinitrophenol and azide and is stimulated by ATP. Mesophyll protoplasts isolated from leaves fed radioactive GA1 retain 20 to 80%o of the radioactivity incorporated by excised leaves. The mechanisms by which plants regulate their GA concentration have not yet been defined. In addition to modulating rates of synthesis or degradation, control might also be achieved through sequestration of GA in compartments from which the hormone could be released in response to various environmental or internal stimuli (22,26). An example of this type of compartmental control mechanism may account for the regulation of stomatal closing by release of ABA from mesophyll chloroplasts (13).Plastids may be sites of both the biosynthetic steps leading to formation of GAs (15,27) and as compartments for their storage (20,21,28). In addition, two laboratories have presented evidence suggesting that GAs may be synthesized or released by plastids upon their illumination by red light (5,8).In this study we have investigated the uptake and subcellular localization of radioactive GA1 applied exogenously to leaves of ' The extreme length and width of cowpea leaves were recorded daily and the area of the leaves was estimated from the product of both.Uptake by Leaves. The epidermis was peeled from the lower side of 6-or 7-day old barley leaves. Two 2-cm long sections (60 jig Chl) then were floated on 2 ml 10-7 M 13H]GA, solution (dissolved in 18 mm K2HPO4, 7 mm citric acid buffer (pH 5.8), 0.5 M mannitol) at 25 C with gentle shaking. The lower epidermis of 5-day-old cowpea leaves was abraded by brushing with carborundum (3). Two 9-mm disks (73 jig Chl) then were cut from the leaves using a cork borer and the discs were floated on the radioactive solution as described for barley. In experiments on the effect of pH on GA, uptake, the discs were floated on radioactive solutions containing 25 mm citric acid, 25 mm K2HPO4, 25 mm Hepes, and 0.5 M mannitol adjusted to the different pH values.The incubations were terminated by removing the radioactive solutions and rinsing the leaf tissue three times with 5 ml buffer solution. The rinsing was carried out over a 15-min period to allow efflux from the extracellular space. The rinsed tissue was then extracted with hot 95% ethanol and the amount of radioactive GA in the extract determined by scintillation counting.For the determination of the subcellular distribution of radioactive GA in barley and for comparison of epidermal versus mesophyll uptake, 12-cm sections (measured from the apex) were cut and the excised leaves were allowed to stand upright for 3 h ...

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“…One approach to understanding phytochromemembrane interactions has been to try to reconstitute a phytochrome-mediated membrane function in vitro. Evidence of phytochrome action in such in vitro experiments has included the regulation of gibberellin levels in proplastids (11), of peroxidase activity in microsomes (24), of exogenous NADP reduction by mitochondria (18,19), and of metabolite permeability in mitochondria and plastids (14,27). We responses of these organelles to actinic R2 and FR were the earliest extensively studied correlations between these two phenomena.…”

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confidence: 99%

Modulation of a Mitochondrial Function by Oat Phytochrome in Vitro

Cedel

Roux²

1980

Plant Physiol.

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ABSTRACTresponses of these organelles to actinic R2 and FR were the earliest extensively studied correlations between these two phenomena. In the present paper, we are reporting our tests of whether Manabe and Furuya's results with pea mitochondria can be obtained with oat mitochondria. We also describe tests of whether exogenously added phytochrome, previously shown to bind to mitochondria with a reproducible stoichiometry (12), could influence the activity of the external NADH-dehydrogenases of mitochondria (22) that we supposed would be accessible to exogenous phytochrome. For these experiments, we have used extensively characterized mitochondrial preparations, and discuss why such characterizations are important for interpretation of the results. MATERIALS AND METHODSMitochondrial Isolation. Mitochondria were isolated from 4-day old etiolated oat seedlings (A vena sativa L., var. Garry) by the procedure of Douce et a. (8). This procedure involves two series of low and high speed centrifugations followed by discontinuous sucrose density gradient centrifugation. Approximately I kg of 4-to 5-cm long oat shoots was harvested after the plants had been chilled to approximately 4 C. The shoots were then exposed to 15 min of white fluorescent light (irradiance of 0.1 mw cm-2) while on ice after harvest and prior to homogenization. All subsequent manipulations were carried out in green safelight at 3-5 C. Mitochondria isolated from these plants were termed "light" mitochondria to contrast them from those isolated from etiolated plants that were not irradiated ("dark" mitochondria). The purified mitochondria were determined to be intact and functioning normally by electron microscopy and biochemical tests described by Douce et al. (8). Their purity was estimated by the quantitative morphometry method described by Cedel and Roux (4). Several random, low-magnification fields taken from various portions of a pellet of purified mitochondria were photographed to obtain the electron micrographs used for the morphometric measurements.Phytochrome Isolation. Phytochrome was isolated by the procedure of Roux et al. (26). All phytochrome used was fully photoreversible, exhibited a peak A for Pr at 667 nm, was at least 50%1o pure and showed 120,000 dalton mol wt subunits on SDS gels. Phytochrome spectral measurements were accomplished using a R-2 ratiospectrophotometer or a Cary model 15 scanning spectrophotometer.Determination of NADPH Levels. NADPH levels were determined by a technique that couples NADPH oxidation to the reduction of DCPIP using a diaphorase enzyme (EC 1.6.99) (16

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Localization of phytochrome in etioplasts and its regulation in vitro of gibberellin levels

Abstract: Etioplasts isolated from barley leaves and purified on a Sephadex G-50 (coarse)

Cited by 73 publications

References 13 publications

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

Uptake and Subcellular Compartmentation of Gibberellin A₁ Applied to Leaves of Barley and Cowpea

Modulation of a Mitochondrial Function by Oat Phytochrome in Vitro

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Localization of phytochrome in etioplasts and its regulation in vitro of gibberellin levels

Abstract: Etioplasts isolated from barley leaves and purified on a Sephadex G-50 (coarse)

Cited by 73 publications

References 13 publications

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

Uptake and Subcellular Compartmentation of Gibberellin A1 Applied to Leaves of Barley and Cowpea

Modulation of a Mitochondrial Function by Oat Phytochrome in Vitro

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Uptake and Subcellular Compartmentation of Gibberellin A₁ Applied to Leaves of Barley and Cowpea