Abscisic acid effects on intracellular pH and ion fluxes in barley leaf segments

Beffagna, N.

doi:10.1034/j.1399-3054.1992.850416.x

Cited by 3 publications

(5 citation statements)

References 15 publications

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“…A number of results previously obtained in our laboratory with different approaches have indicated that treatment with ABA induced a decrease in -∆H + and early cytoplasmic acidification in different adult tissues, these effects also being evident in the absence of activity of the plasmalemma H + -ATPase (Beffagna, 1992 [2] ; Beffagna et al, 1995 [6] , 1997 [7] ). Given the ascer-tained weight of the Ca 2+ pump-mediated Ca 2+ /H + fluxes, the possible involvement of Ca 2+ -ATPase activity in bringing about the changes in H + fluxes observed under ABA treatment was checked.…”

Section: Aba-induced Changes Of H + Fluxes and Ca 2+ -Atpase Activitymentioning

confidence: 90%

“…This material is particularly suitable for in vivo transport studies and accurate pH cyt measurements, and has been extensively characterized in the past in our laboratory (Marrè et al, 1987 [26] ; Beffagna and Romani, 1988 [3] , 1989 [4] , 1991 [5] ; Marrè et al, 1989 [27] ; Romani and Beffagna, 1991 [35] ; Beffagna et al, 1995 [6] ; Meraviglia et al, 1996 [28] ). Some results, aimed at a better understanding of the sequence of events occurring in adult tissues under ABA treatment, are also presented, suggesting the possible involvement of Ca 2+ -ATPase activity in inducing the -∆H + decrease and early cytoplasmic acidification, previously detected in the presence of ABA, either in leaves of barley and Elodea densa or in Arabidopsis thaliana seedlings (Beffagna, 1992 [2] , Beffagna et al, 1995 [6] , 1997 [7] ).…”

Section: Introductionmentioning

confidence: 93%

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H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

2000

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The features of Ca 2+ fluxes, the importance of the Ca 2+ pump-mediated H + /Ca 2+ exchanges at plasmalemma level, and the possible involvement of Ca 2+ -ATPase activity in ABA-induced changes of H + fluxes were studied in Egeria densa leaves. The results presented show that, while in basal conditions no net Ca 2+ flux was evident, a conspicuous Ca 2+ influx (about 1.1 µmol g -1 FW h -1 ) occurred. The concomitant efflux of Ca 2+ was markedly reduced by treatment with 5 µM eosin Y (EY), a specific inhibitor of the Ca 2+ -ATPase, that completely blocked the transport of Ca 2+ after the first 20 -30 min. The decrease in Ca 2+ efflux induced by EY was associated with a significant increase in net H + extrusion (-∆H + ) and a small but significant cytoplasmic alkalinization. The shift of external [Ca 2+ ] from 0.3 to 0.2 mM (reducing Ca 2+ uptake by about 30 %) and the hindrance of Ca 2+ influx by La 3+ were accompanied by progressively higher -∆H + increases, in agreement with a gradual decrease in the activity of a mechanism counteracting the Ca 2+ influx by an nH + /Ca 2+ exchange. The ABA-induced decreases in -∆H + and pH cyt were accompanied by a significant increase in Ca 2+ efflux, all these effects being almost completely suppressed by EY, in line with the view that the ABA effects on H + fluxes are due to activation of the plasmalemma Ca 2+ -ATPase. These results substantially stress the high sensitivity and efficacy of the plasmalemma Ca 2+ pump in removing from the cytoplasm the Ca 2+ taken up, and the importance of the contribution of Ca 2+ pump-mediated H + /Ca 2+ fluxes in bringing about global changes of H + fluxes at plasmalemma level.

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Section: Aba-induced Changes Of H + Fluxes and Ca 2+ -Atpase Activitymentioning

confidence: 90%

Section: Introductionmentioning

confidence: 93%

H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

2000

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“…Marre et al 1983;Mathieu et al 1986;Beffagna & Romani 1991), metabolism (Trockner & E. Marre 1988;M.T. Marre et al 1992), hormones (E. Marre 1979;Beffagna 1992;Cleland etal. 1977;Blatt &Thiel 1993), turgor (Li & Delrot 1987; Curtie;a/.…”

Section: Discussionunclassified

Transmembrane potential‐mediated coupling between H⁺ pump operation and K⁺ fluxes in Elodea densa leaves hyperpolarized by fusicoccin, light or acid load

Bellando

Marré

Sacco

et al. 1995

Plant Cell & Environment

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In isolated Elodea densa leaves, the relationships between H+ extrusion (‐ΔH+), K+ fluxes and membrane potential (Em) were investigated for two different conditions of activation of the ATP‐dependent H+ pump. The ‘basal condition’ (darkness, no pump activator present) was characterized by low values of‐ΔH+ and K+ uptake (ΔK+), wide variability of the −ΔH+/ΔK+ ratio, relatively low membrane polarization and Em values more positive than EK for external K+ concentrations (|K+]o of up to 2mol m−3. A net K+ uptake was seen already at [K+]o below 1 mol m−3, suggesting that K+ influx in this condition was a thermodynamically uphill process involving an active mechanism. When the H+ pump was stimulated by fusicoccin (FC), by cytosol acidification, or by light (the ‘high polarization condition’), K+ influx largely dominated K+ and C− efflux, and the −ΔH+/ΔK+ ratio approached unity. In the range 50 mmol m−3−5 mol m−3 [K+]0, Em was consistently more negative than EK. The curve of K+ influx at [K+]0 ranging from 50 to 5000mmol m−3 fitted a monophasic, hyperbolic curve, with an apparent half saturation value = 0–2 mol m−3. Increasing |K+]0 progressively depolarized Em, counteracting the strong hyperpolarizing effect of FC. The effects of K+ in depolarizing Em were well correlated with the effects on both K+ influx and −ΔH+, suggesting a cause‐effect chain: K+0 influx → depolarization → activation of H+ extrusion. Cs+ competitively inhibited K+ influx much more strongly in the ‘high polarization’ than in the ‘basal’ condition (50% inhibition at [Cs+]/[K+]0 ratios of 1:14 and 1:2, respectively) thus confirming the involvement of different K+ uptake systems in the two conditions. These results suggest that in E. densa leaves two distinct modes of interactions rule the relationships between H+ pump, membrane polarization and K+ transport. At low membrane polarization, corresponding to a low state of activation of the PM H+‐ATPase and to Em values more positive than EK, K+ influx would mainly

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“…An overview of the typical values of cytosolic pH, net H' extrusion and Em obtained in Elodea densa leaves after 120min under the experimental conditions described above is presented in Table 2, which summarizes the results reported in previous works ( M a d et al, 1987;Marre et al, 1989;Beffagna andRomani, 1991: Marre et al, 1992; Marri: M. T. et al, personal communication; Romani and Beffagna, unpublished). The data of Figure 2 show that C1-efflux, measured as release of 36Cl-in the external medium in these conditions, resulted in a maximum with IBA alone, and was progressively lower in the other conditions, according to the following order:…”

Section: Influence Of Cytosolic Ph H+ P U M P Activity and Em On Cl-mentioning

confidence: 83%

“…Alterna-tively, they might be regulated by the hormone either via Em, or via cytosolic pH, these factors being influenced by some mechanism different from the H' pump. In favour of the first hypothesis were some data obtained in barley leaves showing that treatment with a C1channel-blocking agent (DIDS, 4,4-diisothiocyano-2,2-disulfonic acid stilbene) induced a decrease in both intracellular pH a n d net H+ extrusion (Beffagna, 19921, and the results of Schauf a n d Wilson (1987) who detected a selective inhibition of whole-cell C1-currents by ABA in patch-clamped protoplasts of Asclepias tuberosa. In agreement with the possibility that an Em change may act as a signal evoking channel gating are a number of results reported in literature for Ca' ' channels (Schroeder a n d Hagiwara, 19901, K+ channels (Mac Robbie, 1990;Irving et al, 19921, and C1-(anion) channels (Schroeder a n d Keller, 1992).…”

Section: Introductionmentioning

confidence: 99%

Changes in Chloride Fluxes and Cytosolic pH Induced by Abscisic Acid in Elodea densa Leaves

1995

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The effects of ABA on intracellular pH, net H' extrusion, C1-fluxes and Em values were studied in Elodea densa leaves, and the possible relationships between the ABA-induced changes of cytosolic pH and of C1-and H' fluxes were investigated. Cytosolic and vacuolar pH were calculated by the weak acid and weak base distribution method. The data show that, also in this material (a water plant without stomata), ABA induces a decrease in both net H+ extrusion and intracellular pH, and strongly inhibits C1-efflux. No significant effect of ABA is detectable on Em values, either at short or long intervals in the presence or absence of K' . C1-efflux is apparently independent of the activity of the plasmalemma H' pump and of the Em values. Conversely, it strongly depends on the value of cytosolic pH, a larger efflux occurring for the lower pH values both in the presence and in the absence of M A . These results indicate that the ABA-induced cytosolic acidification cannot be the cause but, possibly, a consequence of the decrease in C1-efflux, and are consistent with the hypothesis of a primary role of ABA in regulating C1-ef'flux, presumably by directly affecting a class of C1--permeable channels.I

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Abscisic acid effects on intracellular pH and ion fluxes in barley leaf segments

Cited by 3 publications

References 15 publications

H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

Transmembrane potential‐mediated coupling between H⁺ pump operation and K⁺ fluxes in Elodea densa leaves hyperpolarized by fusicoccin, light or acid load

Changes in Chloride Fluxes and Cytosolic pH Induced by Abscisic Acid in Elodea densa Leaves

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Abscisic acid effects on intracellular pH and ion fluxes in barley leaf segments

Cited by 3 publications

References 15 publications

H+ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca2+‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

H+ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca2+‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

Transmembrane potential‐mediated coupling between H+ pump operation and K+ fluxes in Elodea densa leaves hyperpolarized by fusicoccin, light or acid load

Changes in Chloride Fluxes and Cytosolic pH Induced by Abscisic Acid in Elodea densa Leaves

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H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

H⁺ Fluxes at Plasmalemma Level: In Vivo Evidence for a Significant Contribution of the Ca²⁺‐ATPase and for the Involvement of its Activity in the Abscisic Acid‐Induced Changes in Egeria Densa Leaves

Transmembrane potential‐mediated coupling between H⁺ pump operation and K⁺ fluxes in Elodea densa leaves hyperpolarized by fusicoccin, light or acid load