Energy coupling for membrane hyperpolarization in Lemna: respiration rate, ATP level and membrane potential at low oxygen concentrations

Löppert, H. G.

doi:10.1007/bf00393171

Cited by 20 publications

(4 citation statements)

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“…However, these authors noticed a number of circumstances in which this correlation does not hold. Loppert's data (9) obtained in Lemna at different oxygen partial pressures would suggest that there is no correlation between ATP level and membrane potential, whereas Mimura et al (15) show that ADP and AMP, which increase under anoxia, are competitive inhibitors of plasmalemma ATPase. These findings suggest that factors other than ATP are implicated in the regulation of membrane potential under anoxic conditions.…”

Section: Introductionmentioning

confidence: 96%

H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

Xia¹,

Saglio²

1990

Plant Physiol.

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The relationship between changes in H+ flux and sugar transport in maize Zea mays L. DEA root tips have been investigated using two methods for controlling the cellular nucleotide level: (a) incubation in the presence of a glucose analog, the 2-deoxyglucose, which decreased the ATP level to less than 15% of its initial value within 60 minutes without changing the ADP (15) show that ADP and AMP, which increase under anoxia, are competitive inhibitors of plasmalemma ATPase. These findings suggest that factors other than ATP are implicated in the regulation of membrane potential under anoxic conditions. It is well established that sugar or amino acid transport in plant cells is driven by pmf' and that ATP fuels this electrogenic process (1,6,20,27), but it is difficult to find concurrent in vivo data on cellular free energy change, pmf generation, and substrate transport. Furthermore, the concept that ATP is the only fuel of these processes has been questioned by several reports on the possible involvement of another H+ secreting system linked to a redox chain with NAD(P)H as electron donor and stimulated by ferricyanide (4, 16, 21). Thus, the aim of the study reported here was to examine changes in energy charge, pmf, and substrate transport in a single experimental system.In this paper, the H+ extrusion and sugar transport in maize root tips have been investigated using dGlc and PO2 for controlling the cellular nucleotide level and FC for modulating the activity of the H+-pump. MATERIALS AND METHODS ChemicalsAll the unlabeled chemicals were purchased from Sigma Chemical Co. and were of the highest available purity. D-(U-14C)glucose (11 GBq/mmol) was from Commissariat a l'EnergieAtomique, France; D_(U-_4C)-fructose (11 GBq/ mmol) was from Radiochemical Center, Amersham, England; 3-O-methyl-D-(U-'4C)glucose (1 1.7 GBq/mmol); and 2-deoxy-D-(1-_4C)glucose (2.15 GBq/mmol) were from New England Nuclear. Plant MaterialMaize seeds (Zea mays L. DEA, Pioneer) were germinated in the dark at 250 C on wet filter paper. At 3 d after imbibition, 3 mm primary root tips (2.2 mg fresh weight each) were excised and incubated for 4 h at 25°C in a mineral solution (22), aerated by air bubbling, and buffered by 5 mM MOPS adjusted to pH 6.2 by KOH. In some experiments, the young 3 d seedlings were previously acclimated to anoxia with 18 h incubation period in hypoxia (2-4 kPa 02) as described (24). Transport StudiesRoot tips were placed in groups of 20 in disposable syringes (5 mL) containing 1.9 mL ofthe above medium. The syringes

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Section: Introductionmentioning

confidence: 96%

H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

Xia¹,

Saglio²

1990

Plant Physiol.

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“…If O2 consumption by mitochondrial cytochrome c oxidase governs O2 uptake of the intact tissue, this process should be saturated with O2 at very low concentrations (< 10 pmol -1-' in water, corresponding to < 1 Yo (w/v) in gaseous atmosphere). This condition was indeed experimentally verified in intact Lemna fronds (Loppert, 1983) but, to our knowledge, no corresponding information is available for rapidly growing plant material.…”

Section: Introductionmentioning

confidence: 82%

“…3). However, the low K, of O2 uptake measured in Lemna (Loppert, 1983) and the fact that O2 uptake could not be substantially improved by decreasing the size of the segments ( Table 2) argue against this interpretation. (ii) Mitochondria1 O2 consumption is obscured by the superposition of an O2 uptake process mediated by another, yet unknown, oxidase with a K, for O2 of about 35 pmol -1-'.…”

Section: Discussionmentioning

confidence: 98%

Oxygen Dependence of Elongation Growth and Oxygen Uptake in Maize Coleoptiles

Ding

Schöpfer

1995

Botanica Acta

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Auxin‐mediated elongation growth of maize coleoptile segments is inhibited by reducing the O2 concentration in the incubation medium to GT 100 μmol . 1−1. The half‐maximal elongation rate is reached at 40 μmol . 1−1 O2, i.e. about two orders of magnitude higher than with mitochondrial respiration. O2 uptake of the segments measured under similar conditions with an O2 electrode shows a very similar dependence on O2 concentration. Auxin increases O2 uptake by 5–10% when it induces growth. About 40% of the O2 uptake is insensitive to inhibition by KCN. Auxin has no effect on O2 uptake in the presence of KCN. The possibility that auxin‐mediated elongation growth depends on a KCN‐sensitive oxidative process, other than cytochrome c oxidase‐catalyzed respiration, is discussed.

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“…we find that the NADH oxidase of mature portions of the soybean hypocotyl is n o longer auxin responsive. That plasma membrane-associated NADH oxidase may be stimulated in vivo by auxin is indicated by the previously unexplained stimulation by auxin of oxygen uptake with plant tissues (Polevoy and Salamatova 1977. Loppert 1983.…”

Section: Discussionmentioning

confidence: 99%

Role of plasma membrane redox activities in elongation growth in plants

Moiré

Brightman

et al. 1988

Physiologia Plantarum

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Comparing isolated plasma membrane vesicles and excised hypocotyl segments from etiolated seedlings of soybean [Glycine max (L.) Merr. cv. Williams], certain antiproliferative agents that inhibited growth inhibited plasma membrane redox activities. Additionally, auxins that stimulated growth stimulated plasma membrane redox activities. Hormone stimulation was restricted to NADH oxidase (determined from disappearance of NADH) and was given both by isolated plasma membranes and by a soluhilizedenzyme preparation. Comparing IAA, the native auxin regulator, and 2,4‐D, a synthetic regulator, stimulation was observed, hut the dose‐response curves were different. Yet, the dose‐response relationships of both stimulation of auxin growth and stimulation of NADH oxidase were parallel. Inhibition of auxin‐induced growth by antiproliferative drugs was more complex. Some, like actinomycin D, preferentially inhibited NADH oxidase (EC 1.6.99.2) but inhibited NADH‐ferricya‐nide oxido‐reductase (EC 1.6.99.3) as well. Others, like adriamycin, inhibited primarily the NADH‐ferricyanide oxido‐reductase. Therefore, growth control by auxin appeared to involve NADH oxidase as a rate‐limiting terminal oxidase to link electron flow from NADH to oxygen. This observation may provide a fundamental difference from animal cells. With the latter, impermeant electron acceptors such as diferric transferrin or ferricyanide fulfill such a role. In plants, these impermeant electron acceptors were without effect on growth or were growth inhibitory.

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Energy coupling for membrane hyperpolarization in Lemna: respiration rate, ATP level and membrane potential at low oxygen concentrations

Cited by 20 publications

References 20 publications

H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

Oxygen Dependence of Elongation Growth and Oxygen Uptake in Maize Coleoptiles

Role of plasma membrane redox activities in elongation growth in plants

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Energy coupling for membrane hyperpolarization in Lemna: respiration rate, ATP level and membrane potential at low oxygen concentrations

Cited by 20 publications

References 20 publications

H+ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

H+ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

Oxygen Dependence of Elongation Growth and Oxygen Uptake in Maize Coleoptiles

Role of plasma membrane redox activities in elongation growth in plants

Contact Info

Product

Resources

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H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips

H⁺ Efflux and Hexose Transport under Imposed Energy Status in Maize Root Tips