共查询到20条相似文献,搜索用时 15 毫秒
1.
Previous results with potato tuber discs showed that a treatment with abscisic acid stimulated K+ uptake. In this investigation, we determine the relationship between increased K' uptake and H+extrusion, and Ca2+ fluxes by treating tissues with specific Ca2+ channel blocker (La3+), calmodulin (CaM) inhibitors (chlorpromazine and W7), and with Ca2+ ionophore (A23187). K+ uptake increased with increasing external pH whether tissues were treated with ABA or not. Treatment of tissues with La3+ inhibited K+ uptake, whereas CaM inhibitors have no effect. By contrast ABA and A23187 produced a synergistic effect, suggesting that
ABA may act in part, on K+ uptake, like a Ca2+ agonist, in accord with Huddart's hypothesis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
It is shown that, contrary to what is generally found, treatment with abscisic acid (ABA) of potato leaf tissues resulted
in an increase of K+ uptake. Comparison with other hormones was made: BAP induced an inhibition and GA3 a stimulation of K+ uptake. The uptake was sensitive to several metabolic inhibitors, external pH and ATPase inhibitors while p-chloromercuribenzenesulfonic
acid (PCMBS) had no effect. Uptake kinetics revealed the presence of both saturable and linear components which were both
stimulated by ABA treatment. Our data are consistent with an effect of ABA on the active and passive components of K+ uptake. These results are discussed in relation to the action of ABA on foliar senescence and the action on ion partitioning
in the whole plant. 相似文献
3.
Yanliang Guo Jingyi Zhu Jiahe Liu Yuxing Xue Jingjing Chang Yong Zhang Golam Jalal Ahammed Chunhua Wei Jianxiang Ma Pingfang Li Xian Zhang Hao Li 《Plant, cell & environment》2023,46(1):171-184
Precocious leaf senescence can reduce crop yield and quality by limiting the growth stage. Melatonin has been shown to delay leaf senescence; however, the underlying mechanism remains obscure. Here, we show that melatonin offsets abscisic acid (ABA) to protect photosystem II and delay the senescence of attached old leaves under the light. Melatonin induced H2O2 accumulation accompanied by an upregulation of melon respiratory burst oxidase homolog D (CmRBOHD) under ABA-induced stress. Both melatonin and H2O2 induced the accumulation of cytoplasmic-free Ca2+ ([Ca2+]cyt) in response to ABA, while blocking of Ca2+ influx channels attenuated melatonin- and H2O2-induced ABA tolerance. CmRBOHD overexpression induced [Ca2+]cyt accumulation and delayed leaf senescence, whereas deletion of Arabidopsis AtRBOHD, a homologous gene of CmRBOHD, compromised the melatonin-induced [Ca2+]cyt accumulation and delay of leaf senescence in Arabidopsis under ABA stress. Furthermore, melatonin, H2O2 and Ca2+ attenuated ABA-induced K+ efflux and subsequent cell death. CmRBOHD overexpression and AtRBOHD deletion alleviated and aggravated the ABA-induced K+ efflux, respectively. Taken together, our study unveils a new mechanism by which melatonin offsets ABA action to delay leaf senescence via RBOHD-dependent H2O2 production that triggers [Ca2+]cyt accumulation and subsequently inhibits K+ efflux and delays cell death/leaf senescence in response to ABA. 相似文献
4.
Harrihar A. Pershadsingh Evan B. Stubbs Jr. William D. NoteboomMarie L. Vorbeck Arlene P. Martin 《生物化学与生物物理学报:生物膜》1985,821(3)
The involvement of Ca2+-activated K+ channels in the regulation of the plasma membrane potential and electrogenic uptake of glycine in SP 2/0-AG14 lymphocytes was investigated using the potentiometric indicator 3,3′-diethylthiodicarbocyanine iodide. The resting membrane potential was estimated to be −57 ± 6 mV (n = 4), a value similar to that of normal lymphocytes. The magnitude of the membrane potential and the electrogenic uptake of glycine were dependent on the extracellular K+ concentration, [K+]o, and were significantly enhanced by exogenous calcium. The apparent Vmax of Na+-dependent glycine uptake was doubled in the presence of calcium, whereas the K0.5 was not affected. Ouabain had no influence on the membrane potential under the conditions employed. Additional criteria used to demonstrate the presence of Ca2+-activated K+ channels included the following: (1) addition of EGTA to calcium supplemented cells elicited a rapid depolarization of the membrane potential that was dependent on [K+]o; (2) the calmodulin antagonist, trifluoperazine, depolarized the membrane potential in a dose-dependent and saturable manner with an IC50 of 9.4 μM; and (3) cells treated with the Ca2+-activated K+ channel antagonist, quinine, demonstrated an elevated membrane potential and depressed electrogenic glycine uptake. Results from the present study provide evidence for Ca2+-activated K+ channels in SP 2/0-AG14 lymphocytes, and that their involvement regulates the plasma membrane potential and thereby the electrogenic uptake of Na+-dependent amino acids. 相似文献
5.
Catalina Cabot John V. Sibole Joan Barceló Charlotte Poschenrieder 《Journal of Plant Growth Regulation》2009,28(2):187-192
Previous results showed that in short-term NaCl-treated beans increased leaf abscisic acid (ABA) concentration was triggered
by Na+ but not by Cl-. In this work, the specificity of ABA signaling for Na+ homeostasis was studied by comparing the plant’s responses to solutions that modified accumulation of ABA and/or Na+ uptake and distribution, such as supplemental Ca2+, increased nutrient strength, different isosmotic composition, application of exogenous ABA, fluridone (an ABA inhibitor)
and aminooxiacetic acid (AOA, an ethylene inhibitor). After fluridone pretreatment, salt-treated beans had lower Na+ uptake and higher leaf Na+ exclusion capacity than non-pretreated plants. Moreover, Na+ uptake was increased and leaf Na+ exclusion was decreased by AOA and ABA. NaCl and KCl similarly increased leaf ABA and decreased transpiration rates, whereas
supplemental Ca2+ and increased strength nutrient solution decreased leaf ABA and leaf Na+. These results show (1) a non-ion-specific increase in ABA that probably signaled the osmotic component of salt, and (2)
increased ABA levels that resulted in higher leaf Na+ concentrations due to lower Na+ exclusion or increased root-shoot Na+ translocation. 相似文献
6.
The potassium uptake by potato tuber discs tissues freshly cut and after 24 h of ageing in the presence or not of abscisic
acid was investigated. Uptake kinetics revealed a biphasic dependence on external K+ concentrations. At concentration less than 10 mM, uptake was mediated by a saturable component and a linear component became
apparent at higher concentrations. At low K+ concentrations (lmM), the capacity of K+ uptake diminished by 2 times after ageing. Treatment of tissues with ABA increased the rate of K+ uptake. In both fresh and aged tissues the uptake was strongly enhanced by fusicoccin and decreased by several metabolic
inhibitors and ATPase inhibitors, underlying the active nature of uptake and suggesting the involvement of a plasmalemma H+-ATPase in K+ transport system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Sealed plasma membrane vesicles were obtained in high purity from leaves of Commelina communis L. by aqueous two-phase partitioning. Based on the analysis of a range of markers, the preparations (U3+U3′ phases) were shown to be devoid of tonoplast, Golgi and thylakoid membranes, and showed only trace mitochondrial contamination. One-third of the vesicles were oriented inside out and exhibited ATP-driven 45Ca2+ transport [? 15 pkat (mg protein)−1]. Ca2+ uptake into the vesicles had a pH optimum of 7.2 and apparent Km values for Ca2+ of 4.4 μM and for Mg-ATP of 300 μM. Ca2+ uptake, K+, Mg2+-ATPase (EC 3.6.1.3) activity as well as glucan synthase II (EC 2.4.1.34) activity were all maximal at the same equilibrium density (1.17 g cm−3) on continuous sucrose density gradients. The protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP) did not inhibit the ATP-dependent Ca2+ transport into the vesicles, excluding a Ca2+/H+ exchange driven by a proton gradient. ATP-dependent Ca2+ uptake was inhibited by erythrosin B (I50= 0.1 μM), ruthenium red (I50= 30 μM), La3+ (I50= 10 μM) and vanadate (I50= 500 μM), but not by azide, cyanide and oligomycin. The calmodulin antagonists, trifluoperazine (I50= 70 μM) and W-7 (I50= 100 μM) were also inhibitory, However, this inhibition was not overcome by calmodulin. Trifluoperazine and W-7, on the other hand, stimulated Ca2+ efflux from the vesicles rather than inhibit Ca2+ uptake. Our results demonstrate the presence of a Ca2+-ATPase in the plasma membrane of C. communis. In the intact cell, the enzyme would pump Ca2+ out of the cell. Its high affinity for Ca2+ makes it a likely component involved in adjusting low cytoplasmic Ca2+ levels. No indications for a secondary active Ca2+/H+ transport mechanism in the plasma membrane of C. communis were obtained. Both, the nucleotide specificity and the sensitivity towards vanadate. distinguish the Ca2+-ATPase from the H+-translocating K+. Mg2+-ATPase in C. communis plasma membranes. 相似文献
8.
Abstract— The incubation of brain stem slices from adult rats in a K+-enriched medium containing a 5-HT uptake inhibitor (fluoxetine) significantly increased their capacity to synthesize 5-HT from tryptophan. The K+-induced stimulation of 5-HT synthesis was at least partly dependent on the depletion of the indoleamine in tissues since: (1) a good correlation was found between the respective changes in 5-HT release and synthesis evoked by high K+ concentrations in the presence of various 5-HT uptake inhibitors; (2) the modifications in endogenous 5-HT levels produced by in vim treatments with drugs (reserpine, pargyline) or by incubating slices with 5-HT altered the stimulating effect of high K+ concentrations and fluoxetine on 5-HT synthesis; (3) the replacement of Ca2+ by Co2+ (4 mM) or EGTA (0.1 mM) in the incubating medium completely prevented the increased 5-HT release and synthesis evoked by high K+ concentrations and fluoxetine. The extraction of tryptophan hydroxylase from incubated tissues revealed that the increased 5-HT synthesis occurring in K+-enriched medium was associated with an activation of this enzyme. Kinetic analyses indicated that this activation resulted from an increase in the Vmax of tryptophan hydroxylase, its apparent affinities for both tryptophan and 6-MPH4 being not significantly affected. In contrast to the tryptophan hydroxylase from tissues incubated in normal physiological medium, the activated enzyme from tissues depolarized by K+ was hardly stimulated by Ca2+-mediated phosphorylating conditions. This led to the proposition of a hypothetical model by which the Ca2+ influx produced by the neuronal depolarization would trigger the activity of a Ca2+-dependent protein kinase capable of activating tryptophan hydroxylase. Although this sequence is still largely speculative it must be emphasized that, as expected from such a model, the regional differences in the K+-evoked activation of tryptophan hydroxylase in slices (cerebral cortex > brain stem > spinal cord) were parallel to those of the Ca2+-dependent protein phosphorylation (r= 0.92) and those of the activating effect of phosphorylating conditions on soluble tryptophan hydroxylase (r= 0.96). 相似文献
9.
Using detached leaves of potato plants (Solanum tuberosum cv. Bintje) it was shown that abscisic acid (ABA) induced an oriented transport of ions (86Rb,32P and3SS) towards the hormone-treated leaflet. In order to understand the hormone effect on cell permeability, pretreatment of discs
with hormonal solution was conducted. The pretreatment with ABA stimulated the uptake of K+ simultaneously with the decrease of efflux.
The effect of ABA on ion uptake is compared with the action of other hormones, benzylaminopurine (BAP), gibberellic acid (GA3) known to act over a long distance transport, too.
Three kinds of specificity are underlined: - hormonal specificity (stimulation by ABA and inhibiton by BAP of K+ uptake by foliar tissues); - ionic specificity (ABA increase86Rb influx, but inhibits32P and3SS influx); - tissue specificity shown by a comparative study between foliar tissues (source) and tuber tissues (sink). The
autoradiography of foliar discs demonstrated that a treatment of foliar discs can be used, at least for Rb+ (K), to study role of ABA in long-distance transport.
相似文献
10.
The spinach (Spinacia oleracea L.) leaf plasma membrane Ca2+-ATPase is regulated by calmodulin (3-fold stimulation) and limited proteolysis (trypsin; 4-fold stimulation). The plasma membrane Ca2+-ATPase was identified as a 120-kDa polypeptide on western immunoblots using two different antibodies. During trypsin treatment the 120-kDa band diminished and a new band appeared at 109 kDa. The appearance of the 109-kDa band correlated with the increase in enzyme activity following trypsin treatment. The stimulations by calmodulin and trypsin were not additive, suggesting that the 109-kDa polypeptide represents a Ca2+-ATPase lackin a terminal fragment involved in calmodulin regulation. This was confirmed by 125I-calmodulin overlay studies where calmodulin labeled the 120-kDa band in the presence of Ca2+, while the 109-kDa band did not bind calmodulin. The effects of calmodulin and limited proteolysis on ATP-dependent accumulation of 45Ca2+ in isolated inside-out plasma membrane vesicles were studied, and kinetical analyses performed with respect to Ca2+ and ATP. Calmodulin increased the Vmax. for Ca2+ pumping 3-fold, and reduced Km for Ca2+ from 1.6 to 0.9 µM. The Km for ATP (11 µM) was not affected by calmodulin. The effects of limited proteolysis on the affinities for Ca2+ and ATP were similar to those obtained with calmodulin. Notably, however, limited proteolysis increased the Vmax. for Ca2+ pumping to a higher extent than calmodulin, indicating incomplete calmodulin activation, or removal of an additional inhibitory site by trypsin. 相似文献
11.
Robert S. Siegel Shaowu Xue Yoshiyuki Murata Yingzhen Yang Noriyuki Nishimura Angela Wang Julian I. Schroeder 《The Plant journal : for cell and molecular biology》2009,59(2):207-220
Stomatal closure in response to abscisic acid depends on mechanisms that are mediated by intracellular [Ca2+] ([Ca2+]i), and also on mechanisms that are independent of [Ca2+]i in guard cells. In this study, we addressed three important questions with respect to these two predicted pathways in Arabidopsis thaliana. (i) How large is the relative abscisic acid (ABA)‐induced stomatal closure response in the [Ca2+]i‐elevation‐independent pathway? (ii) How do ABA‐insensitive mutants affect the [Ca2+]i‐elevation‐independent pathway? (iii) Does ABA enhance (prime) the Ca2+ sensitivity of anion and inward‐rectifying K+ channel regulation? We monitored stomatal responses to ABA while experimentally inhibiting [Ca2+]i elevations and clamping [Ca2+]i to resting levels. The absence of [Ca2+]i elevations was confirmed by ratiometric [Ca2+]i imaging experiments. ABA‐induced stomatal closure in the absence of [Ca2+]i elevations above the physiological resting [Ca2+]i showed only approximately 30% of the normal stomatal closure response, and was greatly slowed compared to the response in the presence of [Ca2+]i elevations. The ABA‐insensitive mutants ost1‐2, abi2‐1 and gca2 showed partial stomatal closure responses that correlate with [Ca2+]i‐dependent ABA signaling. Interestingly, patch‐clamp experiments showed that exposure of guard cells to ABA greatly enhances the ability of cytosolic Ca2+ to activate S‐type anion channels and down‐regulate inward‐rectifying K+ channels, providing strong evidence for a Ca2+ sensitivity priming hypothesis. The present study demonstrates and quantifies an attenuated and slowed ABA response when [Ca2+]i elevations are directly inhibited in guard cells. A minimal model is discussed, in which ABA enhances (primes) the [Ca2+]i sensitivity of stomatal closure mechanisms. 相似文献
12.
This report describes K+ efflux, K+ and Ca2+ uptake responses to endothelins (ET-1 and ET-3) in cultured endothelium derived from capillaries of human brain (HBEC). ET-1 dose dependently increased K+ efflux, K+ and Ca2+ uptake in these cells. ET-1 stimulated K+ efflux occurred prior to that of K+ uptake. ET-3 was ineffective. The main contributor to the ET-1 induced K+ uptake was ouabain but not bumetanide-sensitive (Na+-K+-ATPase and Na+-K+-Cl– cotransport activity, respectively). All tested paradigms of ET-1 effects in HBEC were inhibited by selective antagonist of ETA but not ETB receptors and inhibitors of phospholipase C and receptor-operated Ca2+ channels. Activation of protein kinase C (PKC) decreased whereas inhibition of PKC increased the ET-1 stimulated K+ efflux, K+ and Ca2+ uptake in HBEC. The results indicate that ET-1 affects the HBEC ionic transport systems through activation of ETA receptors linked to PLC and modulated by intracellular Ca2+ mobilization and PKC. 相似文献
13.
A possible role for protein kinases in the regulation of GABA exocytosis in nerve endings was investigated. The effect on the release of the radioactive neurotransmitter ([3H]GABA) from mouse brain synaptosomes of several protein kinase inhibitors was estimated after treatment with 37 mM K+ in the absence of external Na+, a condition under which [3H]GABA release is completely Ca2+ dependent. Among the inhibitors one group inhibit the kinases by binding to the catalytic site (i.e. staurosporine and H7) and others (TFP, sphingosine and W7) act on the regulatory site of protein kinases. The compounds of the second group, which are reported to inhibit calmodulin dependent events and the increase in cytosolic Ca2+ (Ca
i
) induced by high K+ depolarization, were the most efficient inhibitors of [3H]GABA release. The selective inhibitor of CaMPK II, KN-62, also markedly diminished [3H]GABA release as well as the increase in Ca
i
induced by high K+. The kinase inhibitors from the first group that are unable to diminish the increase in Ca
i
induced by high K+ were also less efficient inhibitors of [3H]GABA release even at high concentrations. The present results indicate that at the doses tested all the drugs inhibit to some extent the release of the Ca2+ dependent fraction of [3H]GABA perhaps by inhibiting a CaMPK II mediated phosphorylation step triggered by depolarization and facilitated by the elevation of Ca
i
. In addition, the second group of antagonists and KN-62 inhibit the elevation of Ca
i
to high K+ thus exhibiting a higher efficiency on [3H]GABA release than the first group of antagonists. 相似文献
14.
Partial Characterization of K and Ca Uptake Systems in the Halotolerant Alga Dunaliella salina
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The uptake of K+ and Ca2+ in Dunaliella salina is mediated by two distinct carriers: a K+ carrier with a high selectivity against Na+, Li+, and choline+ but not towards Rb+, K+, Cs+, or NH4+, and a Ca2+ carrier with a high selectivity against Mg2+. The latter is specifically blocked by La3+ and by Cd2+. Apparent Km values for K+ and Ca2+ uptake are 2.5 and 0.8 millimolar, respectively, and their maximal calculated fluxes are 22 and 0.8 nanomoles per square meter per second, respectively. Effects of permeable ions and ionophores on K+ and Ca2+ uptake suggest that the driving force for their uptake is the transmembrane electrical potential. Inhibitors of ATP production, typical inhibitors of plasma membrane H+-ATPases and protonionophores inhibit K+ and Ca2+ uptake and accelerate K+ efflux. The results suggest that an H+-ATPase in the cell membrane provides the driving force for K+ and Ca2+ uptake. Efflux measurements from 86Rb+ and 45Ca2+ loaded cells suggest that part of the intracellular K+ and most of the intracellular Ca2+ is nonexchangeable with the extracellular pool. Correlations between phosphate and K+ contents and the effect of phosphate on K+ efflux suggest intracellular associations between K+ and polyphosphates. On the basis of these results, it is suggested that: (a) K+ and Ca2+ uptake in D. salina is driven by the transmembrane electrical potential which is generated by the action of an H+-ATPase of the plasma membrane. (b) Part of the intracellular K+ is associated with polyphosphate bodies, while most of the intracellular Ca2+ is accumulated in intracellular organelles in the algal cells. 相似文献
15.
Plasmalemma-rich microsomal vesicles were prepared from whole leaf and acid-washed epidermal tissue of Vicia faba L. cv. Osnabrücker Markt by aqueous two-phase partitioning in dextran T-500 and polyethylenglycol 1350 aqueous phases. These vesicles were tightly sealed and predominantly right-side out, and contained a K+ -stimulated, mg2+-dependent and vanadate-sensitive ATPase. The enzyme from both tissues exhibited nearly identical properties: pH optimum 6.4, Km for ATP 0.60 mM(whole leaf) and 0.67 mM (epidermis). Vmax -480 nmol (mg protein)1 min1 (whole leaf) and 510 nmol (mg protein)1 min1 (epidermis), I50 (Na3,VO4) 7.5 μM (whole leaf) and 15 μM (epidermis). The enzyme was not inhibited by NO3(50 mM)or sodium azide (I mM). DCCD (20 μM) reduced enzyme activity to 50% (whole leaf) and 58% (epidermis), gramicidin S (20 μM) to 36% (whole leaf) and 41%(epidermis). Ca2+ inhibited the ATPase [I50, C2+: 0.5 mM(whole leaf) and 0.8 mM(epidermis)]. Ca2+ inhibited the ATPase [I50, C2+ 0.5 mM(whole leaf) und 0.8 (epidermis)]. The vanadate-sensitive ATPase from whole leaf and epidermal tissue was slightly but significantly stimulated by fusicoccin (FC) at a concentration (0.13 μM) promoting stomatal opening. The stimulation was not seen in the solubilized ATPase. Stomata of the cultivar used here were insensitive lo (±)ABA up to 2 μM level which is effective in most other cultivars and species. Likewise, at this concentration no effect of ABA on the activity of the epidermal ATPase was observed. The data are discussed with respect to the interaction of FC and ABA with the ATPase. 相似文献
16.
《生物化学与生物物理学报:生物膜》1986,860(1):25-34
Several lipophilic calmodulin antagonists (phenotiazines, butyrophenones and diphenylbutylpiperidines) inhibited Ca2+-induced loss of KCl from human red cells. However, the Ki values for this effect did not bear good correlation with the Ki values reported for well-known calmodulin-dependent systems. In addition, the inhibition was strongly dependent on the haematocrit and valinomycin-induced KCl fluxes were also affected. Added calmodulin did not have any effect on Ca2+-dependent 86Rb uptake by inside-out vesicles derived from red cell membranes whereas stimulation of Ca2+-dependent ATPase was apparent. Lipophilic anticalmodulins at high doses had all kinds of effects on 86Rb uptake by inside-out vesicles: increase, decrease or no change of the fraction of activated vesicles reached at submaximal Ca2+ concentrations, with or without modification of the relative rate of 86Rb uptake. The hydrophylic compound 48/80 decreased the fraction of activated vesicles reached at submaximal Ca2+ concentrations without affecting the relative rate of 86Rb uptake, but this effect took place only at concentrations 10-fold higher than the reported Ki for calmodulin-dependent systems. These results suggest that Ca2+-dependent K+ channels of red cells are not regulated by calmodulin. 相似文献
17.
Eugene Emmer Richard P. Rood John H. Wesolek Michael E. Cohen R. Scott Braithwaite Geoffrey W. G. Sharp Heini Murer Mark Donowitz 《The Journal of membrane biology》1989,108(3):207-215
Summary In rabbit ileum, Ca2+/calmodulin (CaM) appears to be involved in physiologically inhibiting the linked NaCl absorptive process, since inhibitors of Ca2+/CaM stimulate linked Na+ and Cl– absorption. The role of Ca2+/CaM-dependent phosphorylation in regulation of the brush-border Na+/H+ antiporter, which is believed to be part of the neutral linked NaCl absorptive process, was studied using purified brush-border membrane vesicles, which contain both the Na+/H+ antiporter and Ca2+/CaM-dependent protein kinase(s) and its phosphoprotein substrates. Rabbit ileal villus cell brush-border membrane vesicles were prepared by Mg precipitation and depleted of ATP. Using a freezethaw technique, the ATP-depleted vesicles were loaded with Ca2+, CaM, ATP and an ATP-regenerating system consisting of creatine kinase and creatine phosphate. The combination of Ca2+/CaM and ATP inhibited Na+/H+ exchange by 45±13%. This effect was specific since Ca2+/CaM and ATP did not alter diffusive Na+ uptake, Na+-dependent glucose entry, or Na+ or glucose equilibrium volumes. The inhibition of the Na+/H+ exchanger by Ca2+/CaM/ATP was due to an effect on theV
max and not on theK
m
for Na+. In the presence of CaM and ATP, Ca2+ caused a concentration-dependent inhibition of Na+ uptake, with an effect 50% of maximum occurring at 120nm. This Ca2+ concentration dependence was similar to the Ca2+ concentration dependence of Ca2+/CaM-dependent phosphorylation of specific proteins in the vesicles. The Ca2+/CaM/ATP-inhibition of Na+/H+ exchange was reversed by W13, a Ca2+/CaM antagonist, but not by a hydrophobic control, W12, or by H-7, a protein kinase C antagonist. we conclude that Ca2+, acting through CaM, regulates ileal brush-border Na+/H+ exchange, and that this may be involved in the regulation of neutral linked NaCl absorption. 相似文献
18.
Abstract Using the method of compartmental analysis, the ion fluxes and compartment concentrations of Ca2+, K+ and Cl- have been compared in the untreated vegetative frond and the abscisic acid (ABA) induced turion of Spirodela polyrrhiza. The ABA-induced turion is characterized by reduced Ca2+ exchange across the tonoplast and low vacuolar Ca2+ concentration relative to the vegetative frond. In addition the turion exhibits a higher plasmalemma flux with a correspondingly high Ca2+ concentration in the cytoplasm. The concentration of K+ and Cl- is much lower in the cytoplasm of the ABA-induced turion than in the vegetative frond with the influx/efflux ratio at both the plasmalemma and the tonoplast being less than 1, a finding exhibited also in dormant storage tissue. Treatment of vegetative fronds with ABA for 18 h resulted in a reduced K+ plasmalemma efflux relative to untreated vegetative fronds and a concomitant increase in the cytoplasmic concentration. There was no rapid effect of ABA on Ca2+, K+ or Cl- fluxes through either membrane. These results are consistent with the notion that drastic changes in ion fluxes and concentrations in the turion are a secondary consequence of ABA-induced development, possibly due to prior regulation by ABA of enzymes inherent to processes involved in membrane transport. 相似文献
19.
E. L. Voigt R. F. Caitano J. M. Maia S. L. Ferreira-Silva C. E. C. De Macêdo J. A. G. Silveira 《Biologia Plantarum》2009,53(4):764-768
Na+ accumulation was investigated in the roots of 11-d-old cowpea [Vigna unguiculata (L.) Walp.] plants. The relative contribution of different membrane transporters on Na+ uptake was estimated by applying Ca2+, K+, NH4
+, and pharmacological inhibitors. Na+ accumulation into the root symplast was decreased by half in the presence of 1 mM Ca2+ and it was almost abolished by 100 mM K+. The inhibitory effect of external NH4+ on Na+ accumulation was more pronounced in the roots of NH4
+-free growing plants. Na+ accumulation was reduced about 73 % by 0.1 mM flufenamate and it was almost blocked by 2 mM quinine. In addition, 20 mM tetraethylammonium
and 1.0 mM Cs+ decreased Na+ accumulation by 28 and 30 %, respectively. These results evidenced that low-affinity Na+ uptake by cowpea roots depends on Ca2+-sensitive and Ca2+-insensitive pathways. The Ca2+-sensitive pathway is probably mediated by nonselective cation channels and the Ca2+-insensitive one may involve K+ channels and to a lesser extent NH4
+-sensitive K+ transporters. 相似文献
20.
《Plant Science Letters》1984,33(1):103-114
The effects of monovalent cations, inhibitors of metabolism dinitrophenol (DNP), carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), and KCN and temperature variations upon Ca2+ fluxes in intact roots of barley (Hordeum vulgare L. cv. Fergus and Herta) seedlings were investigated. 45Ca2+ influx was depressed in CaSO4-grown (low-salt) plants by the presence of NH4+, K+, or Na+ in the uptake medium. In contrast Ca2+ influx was slightly increased by Li+. In low-salt roots pretreated with KCN and in roots preloaded with K+ (high-K+ plants), the presence of K+ in the medium had no significant effect on Ca2+ influx, while in roots preloaded with Na+, the presence of K+ in the medium depressed Ca2+ influx. In absolute terms, Ca2+ influx was significantly greater in high-salt (both K+ or Na+ preloaded) than in low-salt roots.Patterns of 45Ca2+ efflux in the absence and in the presence of K+, NH4+, or Li+ in the external medium showed that these monovalent cations caused stimulation of 45Ca2+ efflux both from the cytoplasmic and vacuolar phases.It was noted that these modifications of Ca2+ fluxes by monovalent cations are transient and characteristic of a transitional stage of cation uptake by low-salt roots. We conclude that, together with stimulated active H+ efflux (another characteristic of this transitional stage), modifications of Ca2+ fluxes during monovalent cation uptake by low-salt roots is a response directed towards the maintenance of electrical neutrality.Determination of net fluxes revealed that the plants were close to Ca2+ flux equilibrium in the growth medium (0.5 mM CaSO4). Transfer of these plants to 0.5 mM CaSO4 + 0.25 mM K2SO4 caused a net release of CA2+ into the external medium. 相似文献