Response of cytoplasmic pH to anoxia in plant tissues with altered activities of fermentation enzymes: application of methyl phosphonate as an NMR pH probe

Couldwell, Deborah L.; Dunford, Robin; Kruger, Nicholas J.; Lloyd, D. C.; Ratcliffe, George; Smith, Anna M.O.

doi:10.1093/aob/mcn174

Cited by 24 publications

(18 citation statements)

References 49 publications

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“…Resonance line shapes are also narrower at the higher oxygen conditions. This likely reflects enhanced homeostasis (increased uniformity of compartmental ionic environments, and thus uniformity of compartmental chemical shifts; Couldwell et al, 2009). Table I provides the results of quantitative spectral analysis for fully expanded, freshly harvested, mature GR horseweed leaves incubated for 14 h in buffer containing glyphosate under three different conditions: (1) in the dark, immersed in buffer equilibrated with 100% oxygen; (2) in the dark, immersed in buffer equilibrated with air (approximately 20% oxygen); and (3) in the light (150 mE m 22 s 21 ), floating on the surface of buffer without air equilibration.…”

Section: Tissue Assessmentmentioning

confidence: 99%

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

Ge¹,

d’Avignon²,

Ackerman

et al. 2014

Plant Physiology

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Horseweed (Conyza canadensis) is considered a significant glyphosate-resistant (GR) weed in agriculture, spreading to 21 states in the United States and now found globally on five continents. This laboratory previously reported rapid vacuolar sequestration of glyphosate as the mechanism of resistance in GR horseweed. The observation of vacuole sequestration is consistent with the existence of a tonoplast-bound transporter. 31 P-Nuclear magnetic resonance experiments performed in vivo with GR horseweed leaf tissue show that glyphosate entry into the plant cell (cytosolic compartment) is (1) first order in extracellular glyphosate concentration, independent of pH and dependent upon ATP; (2) competitively inhibited by alternative substrates (aminomethyl phosphonate [AMPA] and N-methyl glyphosate [NMG]), which themselves enter the plant cell; and (3) blocked by vanadate, a known inhibitor/blocker of ATP-dependent transporters. Vacuole sequestration of glyphosate is (1) first order in cytosolic glyphosate concentration and dependent upon ATP; (2) competitively inhibited by alternative substrates (AMPA and NMG), which themselves enter the plant vacuole; and (3) saturable.31 P-Nuclear magnetic resonance findings with GR horseweed are consistent with the active transport of glyphosate and alternative substrates (AMPA and NMG) across the plasma membrane and tonoplast in a manner characteristic of ATP-binding cassette transporters, similar to those that have been identified in mammalian cells.

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Section: Tissue Assessmentmentioning

confidence: 99%

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

Ge¹,

d’Avignon²,

Ackerman

et al. 2014

Plant Physiology

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“…However, the mechanisms of Pi transfer across the tonoplast remain poorly understood. In this study, the utilization of MeP, which is not metabolized (Couldwell et al, 2009) and does not participate in cell energy metabolism, permitted us both to mimic Pi movements between the cytoplasmic and vacuolar compartments and to interfere in situ with Pi transport. Our results indicate that MeP is readily incorporated by plant cells, provided that either Pi is absent from the external medium or MeP is present in large excess, since the transport of MeP across plasmalemma was competitively inhibited by Pi.…”

Section: Incorporation Of Mep To Cellsmentioning

confidence: 99%

“…We also used a Pi analog, methylphosphonate (MeP), which has several advantages: (1) it mimics Pi perception by plant cells but, unlike Pi, is not metabolized and is nontoxic in the short term (Couldwell et al, 2009); (2) its 31 P-NMR signal displays a broad amplitude of pH-related shift with pKa at 7.5 (DeFronzo and Gillies, 1987), thus facilitating the discrimination between cyt sol -MeP and org mp -MeP pools (Lebrun-Garcia et al, 2002); and (3) its signals do not overlap with those of Pi and phosphorylated metabolites (Gout et al, 2001).…”

mentioning

confidence: 99%

Phosphate (Pi) Starvation Effect on the Cytosolic Pi Concentration and Pi Exchanges across the Tonoplast in Plant Cells: An in Vivo 31P-Nuclear Magnetic Resonance Study Using Methylphosphonate as a Pi Analog

et al. 2009

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In vivo 31P-NMR analyses showed that the phosphate (Pi) concentration in the cytosol of sycamore (Acer pseudoplatanus) and Arabidopsis (Arabidopsis thaliana) cells was much lower than the cytoplasmic Pi concentrations usually considered (60–80 μm instead of >1 mm) and that it dropped very rapidly following the onset of Pi starvation. The Pi efflux from the vacuole was insufficient to compensate for the absence of external Pi supply, suggesting that the drop of cytosolic Pi might be the first endogenous signal triggering the Pi starvation rescue metabolism. Successive short sequences of Pi supply and deprivation showed that added Pi transiently accumulated in the cytosol, then in the stroma and matrix of organelles bounded by two membranes (plastids and mitochondria, respectively), and subsequently in the vacuole. The Pi analog methylphosphonate (MeP) was used to analyze Pi exchanges across the tonoplast. MeP incorporated into cells via the Pi carrier of the plasma membrane; it accumulated massively in the cytosol and prevented Pi efflux from the vacuole. This blocking of vacuolar Pi efflux was confirmed by in vitro assays with purified vacuoles. Subsequent incorporation of Pi into the cells triggered a massive transfer of MeP from the cytosol to the vacuole. Mechanisms for Pi exchanges across the tonoplast are discussed in the light of the low cytosolic Pi level, the cell response to Pi starvation, and the Pi/MeP interactive effects.

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“…However, in leaves of SSG-59-3, activity increased during 6 to 72 h of flooding stress from 30 to 200% as compared to that in control plants. Induction in LDH under waterlogging conditions has been reported in barley, wheat and rice (Hoffman et al 1986;Couldwell et al 2009). …”

Section: Resultsmentioning

confidence: 97%

Activities of enzymes of fermentation pathways in the leaves and roots of contrasting cultivars of sorghum (Sorghum Bicolor L.) during flooding

Jain

Singla

Jain

et al. 2010

Physiol Mol Biol Plants

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Flooding evoked a differential response in the activities of enzymes of fermentation pathway in leaves and roots of flood sensitive (S-308) and flood-tolerant (SSG-59-3) cultivars of sorghum. Activities of alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH) and alanine aminotransferase (AlaAT) enhanced in roots of SSG-59-3 during 72 h of flooding. In contrast, a transient increase in the activities was discerned in roots of S-308 up to 24 h flooding followed by a decline in activities of these enzymes. In leaves of SSG-59-3, the activities of ADH and LDH increased to about three fold during flooding stress as compared to that in the non-flooded control plants. Though elevation in activities of these enzymes was observed in leaves of S-308 up to 48 h of flooding, the magnitude of enhancement was much lower than that in SSG-59-3. Alanine aminotranferase activity depressed in leaves of both the cultivars but the level of decline was more pronounced in sensitive cultivar S-308 as compare to tolerant SSG-59-3. The amount of alcohol, lactic acid and alanine were higher in both roots and leaves of SSG-59-3 than that in S-308 during flooding stress. It is thus apparent that roots and leaves of flood tolerant variety tends to attain greater capacity to perform reactions of various fermentation pathways to sustain production of ATP under flooded conditions.

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Response of cytoplasmic pH to anoxia in plant tissues with altered activities of fermentation enzymes: application of methyl phosphonate as an NMR pH probe

Cited by 24 publications

References 49 publications

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

In Vivo 31P-Nuclear Magnetic Resonance Studies of Glyphosate Uptake, Vacuolar Sequestration, and Tonoplast Pump Activity in Glyphosate-Resistant Horseweed

Phosphate (Pi) Starvation Effect on the Cytosolic Pi Concentration and Pi Exchanges across the Tonoplast in Plant Cells: An in Vivo 31P-Nuclear Magnetic Resonance Study Using Methylphosphonate as a Pi Analog

Activities of enzymes of fermentation pathways in the leaves and roots of contrasting cultivars of sorghum (Sorghum Bicolor L.) during flooding

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