Active swelling and acetate uptake in corn mitochondria

Wilson, Robert H.; Hanson, James A.; Mollenhauer, Hilton H.

doi:10.1021/bi00831a055

Cited by 26 publications

(28 citation statements)

References 33 publications

(47 reference statements)

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“…The indifference to substrate suggests that it is the common coupling mechanism associated with electron transport which is responding. In the absence of an anion which will react with the coupling mechanism (e.g., phosphate) only efflux pumping of KCI (contraction) is seen (20), and here the only cation promotion of respiration is with exogenous Isolation of corn mitochondria with 5 mm EDTA improved respiratory control and resistance to aging at ice temperatures (Table III). Addition of 5 mM Mg2+ to the isolation medium had no effect, but when 50 mm phosphate was also added, respiratory control was high and the mitochondria were resistant to aging.…”

Section: Methodsmentioning

confidence: 91%

“…Activation here lies with the coupling mechanism, and responses are obtained with all respiratory substrates. The postulated mechanism is one of active anion transport and is discussed fully in recent papers (8,10,17,20 (12) and general ATPase activity (13,17). This suggests that metals forming stable bonds are also required so that the time-dependent coupling necessary for ATPase can occur.…”

Section: Methodsmentioning

confidence: 98%

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Divalent Cation Stimulation of Substrate Oxidation by Corn Mitochondria

et al. 1970

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The oxidation of reduced nicotinamide adenine dinucleotide, malate-pyruvate, and succinate by corn mitochondria in buffered 0.2 M KCl was determined as a function of divalent cations. Ni2+, Mg2+, Co2+, Ca2+, Mn2+, Sr2+, and Ba2+ stimulated reduced nicotinamide adenine dinucleotide oxidation in the absence of inorganic phosphate, with Ca2+ and Sr2+ having the greatest effect. Malate-pyruvate and succinate oxidation was stimulated by Ca2+, Ba2+, and Sr2+, but only in the presence of inorganic phosphate. Ca2+, Sr2+, and Ba2+ produced a simulated state 4 to state 3 transition with all three substrates, but only with malate-pyruvate and succinate was there a return to state 4. The order of divalent cation effectiveness suggests that the rate of water substitution from the cation inner coordination hydration sphere may be a rate-limiting step in certain mitochondrial reactions involving electron transport and phosphorylation.Plant mitochondria readily oxidize exogenous reduced nicotinamide adenine dinucleotide by a pathway stimulated by salts in general and by divalent cations in particular (6, 9). Hackett (6) found that the divalent cation stimulation was greater than that due to the ionic strength effect of monovalent salts. Associated with the respiratory stimulation was a light absorbancy increase, indicative of structural changes. Hackett suggested that the stimulation was due to either a greater NADH permeability or a release of some limiting step in the respiratory chain which might be the breakdown of high energy intermediates.The oxidation of NADH by corn mitochondria is stimulated by Ca2+ (17), but this is not true for malate-pyruvate or succinate oxidation (7). Only in the presence of inorganic phosphate is organic acid oxidation promoted and this can be attributed to the coupling of respiration to phosphate transport (10, 16). Hence, if Ca2+ is enhancing substrate permeability, it does so only for NADH. It seems likely that Hackett's second alternative is more probable; divalent cations release some rate-limiting step of the NADH oxidation pathway.The Ca2+-stimulated oxidation of NADH is accompanied by extra Ca2+ binding (10). When respiration ceases, the Ca2+ is released. Hanson and Miller (8) METHODSIsolation of Mitochondria. Mitochondria were isolated from 3-day-old corn shoots (Zea mays L., WF9 X M14) by a procedure similar to that used by Kenefick and Hanson (10). Corn seedlings were grown on paper toweling saturated with a 0.1 mm CaCl2 solution. Approximately 100 g of corn shoots were ground in an ice-cold mortar with 200 ml of 0.5 M sucrose, 50 mM tris-HCl (pH 7.5), 50 mm KH2PO4, and 5 mm disodium EDTA (pH 7.5). The homogenate was strained through four layers of cheesecloth and cleared of cell debris by centrifuging at 1,500g for 10 min, and the mitochondria were collected by centrifugation at 28,00g for 5 min. The mitochondria were then resuspended in a total of 50 ml of 0.4 M sucrose and again centrifuged at 1 ,500g for 10 min. The supernatant was decanted into clean tubes and 10 ml o...

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Section: Methodsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 98%

Divalent Cation Stimulation of Substrate Oxidation by Corn Mitochondria

et al. 1970

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“…Phloem sieve tubes and some adjacent parenchyma cells contain (12,24,26). Swelling involves the unfolding of the inner membrane and a decrease in the amorphous matrix, while contraction involves the infolding of the inner membrane and increase in matrix density.…”

mentioning

confidence: 99%

“…It is generally thought that swollen corn mitochondria have very few cristae and a matrix that stains only lightly, that contracted mitochondria have many inflated cristae and a matrix that becomes densely stained, and that partially swollen mitochondria are intermediate (12,24,26). Swelling involves the unfolding of the inner membrane and a decrease in the amorphous matrix, while contraction involves the infolding of the inner membrane and increase in matrix density.…”

mentioning

confidence: 99%

Corn Mitochondrial Swelling and Contraction—an Alternate Interpretation

Malone¹,

Koeppe²,

Miller³

1974

Plant Physiol.

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Mitochondria isolated from 3-day-old etiolated corn shoots (Zea mays L.) can be categorized into three separate groups, each group characteristic of the cell type from which the mitochondria were isolated. Phloem sieve tubes and some adjacent parenchyma cells contain (12,24,26). Swelling involves the unfolding of the inner membrane and a decrease in the amorphous matrix, while contraction involves the infolding of the inner membrane and increase in matrix density. The presence of contracted, partially swollen, and swollen mitochondria in experimental in vitro preparations that should contain only contracted (or swollen) mitochondria is believed to result from mitochondria responding at different rates (26). A ready reversibility has been reported to exist between swollen, partially swollen, and contracted mitochondria (24).In vivo differences in the number of cristae and amount of amorphous matrix in different cell types for several species of plants have been reported (5, 7-9, 13, 16, 19, 22). Chrispeels et al. (6) Isolated mitochondria were fixed either while they were suspended or after being pelleted at 12,000 rpm for 10 min. Fixatives for isolated mitochondria or intact shoots were 1 or 2% glutaraldehyde either in 0.1 M phosphate buffer or in 0.2 M cacodylate buffer (pH 7.4) followed by 1 % OsO in the respective buffer; or only 1 % OSO4 in 0.1 M phosphate buffer or 0.2 M cacodylate buffer. Dehydration was in a graded ethyl alcohol series, and propylene oxide was used as a solvent for the Epon embedment (15).In vivo mitochondrial contractions were obtained by treating 1-mm thick sections of corn shoots with 2.5 mM 2DOG2 for 20 min (11). The sections were then fixed in 2% glutaraldehyde in 0.2 M cacodylate buffer.One-,um thick plastic sections of whole plant material were cut and observed with phase contrast optics for orientation purposes. Subsequently, thin plastic sections were cut from the adjacent area of the block. All thin sections were observed on an RCA EMU4 or Siemens Elmiskop I electron microscope after staining in uranyl acetate (23) and lead citrate (21).Areas of I. C. and 0. C. of type III mitochondria were determined by superimposing a dot grid on a micrograph and counting dots falling in the compartments. RESULTSMitochondrial profiles fell into three readily recognizable types and were classified according to the type which they most

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“…Numerous studies (3,13,18,22) have demonstrated a passive, energy-independent swelling of plant mitochondria in the presence of isomolar salt solutions, or isomolar solutions of monosaccharide sugars. The existence of an energy-dependent (active) swelling component in plant mitochondria has also been demonstrated (2,5,19,21). Addition of certain oxidizable substrates to swollen mitochondria results in an immediate rapid contraction of the mitochondria while the addition of ATP initiates contraction of swollen corn mitochondria (18), but not swollen castor bean endosperm mitochondria (20).…”

mentioning

confidence: 94%

Swelling and Contraction of Mitochondria from Cold-hardened and Nonhardened Wheat and Rye Seedlings

Pomeroy

1976

Plant Physiol.

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A comparison of mitochondria isolated from 2 and 24 C grown winter wheat (Triticum aestivum L.) and winter rye (Secak cereak L.) seedlings revealed no correlation between changes in swelling and contraction characteristics and extent of cold hardiness. The swelling response changed markedly due to growth at low temperature, but the change was similar for the four cultivars examined. The swelling response was also observed to change rapidly during aging of isolated mitochondria, either at 2 or 24 C. Spontaneously swollen mitochondria, isolated from 24 C grown seedlings, contracted abruptly upon addition of certain oxidizable substrates, but this response was lost when seedlings were transferred from 24 to 2 C. Studies on the effect of various substrates and respiratory inhibitors on the swelling and contraction responses indicate that inhibitors which reduce or stop electron flow through the electron transport chain also inhibit substrate induced mitochondrial contraction.Although the swelling and contraction characteristics of isolated plant mitochondria have been thoroughly investigated, the mechanisms involved in these processes are not completely understood. Numerous studies (3,13,18,22) have demonstrated a passive, energy-independent swelling of plant mitochondria in the presence of isomolar salt solutions, or isomolar solutions of monosaccharide sugars. The existence of an energy-dependent (active) swelling component in plant mitochondria has also been demonstrated (2,5,19,21). Addition of certain oxidizable substrates to swollen mitochondria results in an immediate rapid contraction of the mitochondria while the addition of ATP initiates contraction of swollen corn mitochondria (18), but not swollen castor bean endosperm mitochondria (20). Earlier studies on the effect of specific inhibitors of electron transport and oxidative phosphorylation on swelling and contraction (18,20) postulated that high energy intermediates are associated with the active swelling and contraction observed in plant mitochondria. More recent investigations of energized swelling and contraction have led to interpretation of these phenomena in chemiosmotic terms, suggesting that the energy required is derived from changes in the electrochemical proton gradient (2).Recent studies (11,15) in our laboratories on the mechanism of cold hardening in plants have been directed to investigations of structural and functional properties of wheat and rye mitochondria in relation to growth at low temperature. These studies have revealed a marked increase in the level of fatty acid unsaturation during growth at low temperature, but no differences were observed among cultivars of contrasting cold hardiness. The functional properties of mitochondria from cold hardy cultivars were similar to those from less hardy cultivars. Electron spin resonance studies identified three possible temperature-dependent structural transitions in the mitochondrial membranes, and the shift in one of these appeared to be quantitatively greater in the cold hardy ...

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Active swelling and acetate uptake in corn mitochondria

Cited by 26 publications

References 33 publications

Divalent Cation Stimulation of Substrate Oxidation by Corn Mitochondria

Divalent Cation Stimulation of Substrate Oxidation by Corn Mitochondria

Corn Mitochondrial Swelling and Contraction—an Alternate Interpretation

Swelling and Contraction of Mitochondria from Cold-hardened and Nonhardened Wheat and Rye Seedlings

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