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1.
Emilia Ballesteros Eduardo Blumwald Juan Pedro Donaire rés Belver 《Physiologia plantarum》1997,99(2):328-334
Na+ transport across the tonoplast and its accumulation in the vacuoles is of crucial importance for plant adaptation to salinity. Mild and severe salt stress increased both ATP- and PPi-dependent H+ transport in tonoplast vesicles from sunflower seedling roots, suggesting the possibility that a Na+/H+ antiport system could be operating in such vesicles under salt conditions (E. Ballesteros et al. 1996. Physiol. Plant. 97: 259–268). During a mild salt stress, Na+ was mainly accumulated in the roots. Under a more severe salt treatment, Na+ was equally distributed in shoots and roots. In contrast to what was observed with Na+, all the salt treatments reduced the shoot K+ content. Dissipation by Na+ of the H+ gradient generated by the tonoplast H+-ATPase, monitored as fluorescence quenching of acridine orange, was used to measure Na+/H+ exchange across tonoplast-enriched vesicles isolated by sucrose gradient centrifugation from sunflower (Helianthus annuus L.) roots treated for 3 days with different NaCl regimes. Salt treatments induced a Na+/H+ exchange activity, which displayed saturation kinetics for Na+ added to the assay medium. This activity was partially inhibited by 125 μM amiloride, a competitive inhibitor of Na+/H+ antiports. No Na+/H+ exchange was detected in vesicles from control roots. The activity was specific for Na+. since K+ added to the assay medium slightly dissipated H+ gradients and displayed non-saturating kinetics for all salt treatments. Apparent Km for Na+/H+ exchange in tonoplast vesicles from 150 mM NaCl-treated roots was lower than that of 75 mM NaCl-treated roots, Vmax remaining unchanged. The results suggest that the existence of a specific Na+/H+ exchange activity in tonoplast-enriched vesicle fractions, induced by salt stress, could represent an adaptative response in sunflower plants, moderately tolerant to salinity. 相似文献
2.
Large-scale preparation of highly purified tonoplast from cucumber (Cucumis sativus L.) roots was obtained after centrifugation of microsome pellet (10,000 – 80,000 g) on discontinuous sucrose density gradient
(20, 28, 32 and 42 %). Lack of PEP carboxylase (cytosol marker) and cytochrome c oxidase (mitochondrial marker) together with
a slight activity of VO4-ATPase (plasma membrane marker) and NADH-cytochrome c reductase (ER marker) in tonoplast preparation confirmed its high purity.
Using latency of nitrate-inhibited ATPase and H+ pumping as criteria it was established that the majority of tonoplast vesicles were sealed and oriented right(cytoplasmic)-side-out.
Strong acidification of the interior of vesicles observed at the presence of both, ATP and PPi, confirmed that obtained tonoplast contains two classes of proton pumps: V-ATPase and H+PPiase.
To examine and characterise of proton-transport systems in tonoplast, the effect of various inhibitors on H+ pumping and hydrolytic activities of ATPase and PPiase were measured. ATP-dependent activities (H+ flux and ATP hydrolysis) were specifically decreased by nitrate and bafilomycin A1, whereas the PPiase activities were reduced in the presence of fluoride and Na+ ions. Both enzymes showed a similar sensitivity to DCCD and DES. The results of experiments with KCl and NaCl suggested that
the vacuolar ATPase was stimulated by Cl−, whereas the vacuolar Ppiase requires K+ ions for its activity. 相似文献
3.
Properties of proton and sugar transport at the tonoplast of tomato (Lycopersicon esculentum) fruit 总被引:1,自引:0,他引:1
Tonoplast vesicles were isolated from tomato (Lycopersicon esculentum Mill.) fruit pericarp and purified on a discontinuous sucrose gradient. ATPase activity was inhibited by nitrate and bafilomycin A1 but was insensitive to vanadate and azide. PPase hydrolytic activity was inhibited by NaF but was insensitive to nitrate, bafilomycin A1 vanadate and azide. Kimetic studies of PPase activity gave an apparent Km, for PP3 of 18 μM. Identical distributions of bafilomycin- and NO3-sensitive ATPase activities within continuous sucrose density gradients, confirmed that bafilomycin-sensitive ATPase activity is a suitable marker for the tonoplast. By comparing the distribution of bafilomycin-sensitive ATPase activity with that of PPase activity, it was possible to locate the PPase enzyme exclusively at the tonoplast. The apparent density of the tonoplast did not change during fruit development. Measurements of tonoplast PPase and ATPase activities during fruit development over a 35-day period revealed an 80% reduction in PPase specific activity and a small decrease in ATPase specific activity. ATP- and PP1-dependent ΔpH generation was measured by the quenching of quinacrine fluorescence in tonoplast vesicles prepared on a discontinuous Dextran gradient. No H+ efflux was detected on the addition of sucrose to energized vesicles. Therefore a H+/sucrose antiport may not be the mechanism of sucrose uptake at the tomato fruit tonoplast. Similar results were obtained with glucose, fructose and sorbitol. The lack of ATP (or PP1) stimulation of [14C]-sucrose uptake also suggested that an antiport was not involved. Initial uptake rates of radiolabelled glucose and fructose were almost double that for sucrose. The inhibition of hexose uptake by p-chloromercuribenzene sulphonate (PCMBS) implicated the involvement of a carrier. Therefore storage of hexose in the tomato fruit vacuole and maintenance of a downhill sucrose concentration gradient into sink cells is likely to be regulated by the activity of sucrose metabolizing enzymes, rather than by energy-requiring uptake mechanisms at the tonoplast. 相似文献
4.
The co-ordinated action of the two proton-transporting enzymes at the tonoplast of the CAM plants. daigremontiana, viz. the ATPase and the PPiase, was studied by measuring fluorescent dye quenching. The initial rates of ATP and PPi-dependent H+ transport into tonoplast vesicles were additive, i.e. the sum of the rates obtained with each substrate alone was in the range obtained with both substrates added together at the same time. Conversely, the activities of the two H+ pumps were non-additive in establishing the steady-state level, indicating that the final steady state was under thermodynamic control of a maximal attainable proton gradient. The initial rates of ATP-dependent H+ transport were stimulated enormously if ATP was added a few minutes after pre-energization of the vesicles with PPi. This stimulation was observed only when the PPiase was active. A similar effect was not found for PPi-dependent H+ transport after pre-energization with ATP. Hence, a PPiase-activated ATP-dependent H+ transport can be distinguished from the basic ATP- and the basic PPi-dependent H+ transport. In parallel a PPi-dependent stimulation of ATP hydrolysis in the absence of ionophores was measured, which can only be attributed to the activity of the PPiase. PPiase-activated ATP-dependent H+ transport depends on the presence of permeant anions. It shows properties of both H+ transport activities, i.e. the chloride and malate stimulation and the DCCD inhibition of the ATP-dependent H+ transport activity, the nitrate stimulation and the KF inhibition of the PPi-dependent H+ transport activity. Only MgPPi and MgATP were effective as the respective substrates. The PPiase-activated ATP-dependent H+ transport had a half life of about 5–9 minutes. It is concluded that the PPiase may play an important role in kinetic regulation of the ATPase, and implications for CAM metabolism are discussed. 相似文献
5.
Hans Peter Getz 《Planta》1991,185(2):261-268
Sucrose uptake into tonoplast vesicles, which were prepared from red beet (Beta vulgaris L.) vacuoles isolated by two different methods, was stimulated by MgATP. Using the same medium as for osmotic disruption of vacuoles, membrane vesicles were prepared from tissue homogenates of dormant red beet roots and separated by high-speed centrifugation through a discontinuous dextran gradient. A low-density microsomal fraction highly enriched in tonoplast vesicles could be further purified from contaminating ER vesicles by inclusion of 5 mM MgCl2 in the homogenization medium. These vesicles were able to transport sucrose in an ATP-dependent manner against a concentration gradient, whereas vesicles from regions of other densities lacked this feature, indicating that ATP stimulation of sucrose uptake took place only at the tonoplast membrane. Sucrose uptake was optimal at pH 7 in the presence of MgATP and could be stimulated by superimposed pH gradients (vesicle interior acidic) in the absence of MgATP, which is consistent with the operation of a sucrose/H+-antiporter at the tonoplast. Tonoplast vesicles, obtained in high yield from tissue homogenates of red beet roots, exhibited sugar-uptake characteristics comparable to those of intact vacuoles; these characteristics included similarities in K
m (1.7 mM), sensitivity to inhibitors and specificity for sucrose.Many experiments were carried out at the Experiment Station of the HSPA, Aiea, Hawaii and financed by an NSF grant to Dr. Maretzki and Mrs. M. Thom. 相似文献
6.
A salt-tolerant stable cell-suspension culture from the halophyte Mesembryanthemum crystallinum L. has been established from calli generated from leaves of 6-week-old well-watered plants. Optimal cell growth was observed
in the presence of 200 mM NaCl, and within 7 d cells were able to concentrate Na+ to levels exceeding those in the growth medium. Accumulation of Na+ was paralled by increases in the compatible solute pinitol and myo-inositol methyl transferase (IMT), a key enzyme in pinitol biosynthesis. Increasing concentrations of NaCl stimulated the
activities of tonoplast and plasma-membrane H+-ATPases. Immunodetection of the ATPases showed that the increased activity was not due to changes in protein amount that
could be attributed to treatment conditions. A specific role for these mechanisms in salt-adaptation is supported by the inability
of mannitol-induced water stress to elicit the same responses, and the absence of enzyme activity and protein expression associated
with Crassulacean acid metabolism in the cells. Results demonstrate that these M. crystallinum cell suspensions show a halophytic growth response, comparable to that of the whole plant, and thus provide a valuable tool
for studying signaling and biochemical pathways involved in salt recognition and response.
Received: 18 June 1998 / Accepted: 22 August 1998 相似文献
7.
8.
Summary. The vacuolar H+-translocating inorganic pyrophosphatase (H+-PPase) uses pyrophosphate as substrate to generate the proton electrochemical gradient across the vacuolar membrane to acidify
vacuoles in plant cells. The heterologous expression of H+-PPase genes (TsVP from Thellungiella halophila and AVP1 from Arabidopsis thaliana) improved the salt tolerance of tobacco plants. Under salt stress, the transgenic seedlings showed much better growth and
greater fresh weight than wild-type plants, and their protoplasts had a normal appearance and greater vigor. The cytoplasmic
and vacuolar pH in transgenic and wild-type cells were measured with a pH-sensitive fluorescence indicator. The results showed
that heterologous expression of H+-PPase produced an enhanced proton electrochemical gradient across the vacuolar membrane, which accelerated the sequestration
of sodium ions into the vacuole. More Na+ accumulated in the vacuoles of transgenic cells under salt (NaCl) stress, revealed by staining with the fluorescent indicator
Sodium Green. It was concluded that the tonoplast-resident H+-PPase plays important roles in the maintenance of the proton gradient across the vacuolar membrane and the compartmentation
of Na+ within vacuoles, and heterologous expression of this protein enhanced the electrochemical gradient across the vacuolar membrane,
thereby improving the salt tolerance of tobacco cells.
Correspondence: J.-R. Zhang, School of Life Science, Shandong University, 27 Shanda South Road, Jinan, People’s Republic of
China 250100. 相似文献
9.
A Ca2+-ATPase and a Mg2+/H+-antiporter are present on tonoplast membranes from roots of Zea mays L. 总被引:1,自引:0,他引:1
The primary or secondary energized transport of Ca2+, Mg2+ and H+ into tonoplast membrane vesicles from roots of Zea mays L. seedlings was studied photometrically by using the fluorescent Ca2+ indicator Indo 1 and the pH indicator neutral red. The localization of an ATP-dependent, vanadate-sensitive Ca2+ pump on tonoplast-type vesicles was demonstrated by the co-migration of the Ca2+-pumping and tonoplast H+-pyrophosphatase (PPiase) activity on continuous sucrose density gradients. In ER-membrane fractions, only a low Ca2+-pumping activity could be detected. The ATP-dependent Ca2+ uptake into tonoplast vesicles (using Ca2+ concentrations from 0.8–1 μM) was completely inhibited by the Ca2+ ionophore ionomycin (1 μM) whereas the protonophore nigericin (1 μM) which eliminates ATP-dependent intravesicular H+ accumulation had no effect. Vanadate (IC50 = 43 μM) and diethylstilbesterol (IC50 = 5.2 μM) were potent inhibitors of this type of Ca2+ transport. The nucleotides GTP, UTP, ITP, and ADP gave 27%–50% of the ATP-dependent activity (K m = 0.41 mM). From these results, it was suggested that this ATP-dependent high-affinity Ca2+ transport mechanism is the only functioning Ca2+ transporter of the tonoplast under in-vivo conditions i.e. under the low cytosolic Ca2+ concentration. In contrast, the secondary energized Ca2+-transport mechanism of the tonoplast, the low-affinity Ca2+/H+-antiporter, which was reported to allow the uptake of Ca2+ in exchange for H+, functions chiefly as an Mg2+ transporter under physiological conditions because cytosolic Mg2+ is several orders of magnitude higher than the Ca2+ concentration. This conclusion was deduced from experiments showing that Mg2+ ions in a concentration range of 0.01 to 1 mM triggered a fast efflux of H+ from acid-loaded vesicles. Furthermore, the proton-pumping activity of the tonoplast H+-ATPase and H+-PPiase was found to be influenced by Ca2+ differently from and independently of the Mg2+ concentration. Calcium was a strong inhibitor for the H+-PPiase (IC50 = 18 μM, Hill coefficient nH = 1.7) but a weak one for the H+-ATPase (IC50 = 330 μM, nH = 1). From these results it is suggested that at the tonoplast membrane a functional interaction exists between (i) the Ca2+-and Mg2+-regulated H+-PPiase, (ii) the newly described high-affinity Ca2+-AT-Pase, (iii) the low-affinity Mg2+(Ca2+)/H+-antiporter and (iv) the H2+-ATPase. 相似文献
10.
R. Ratajczak 《Plant biology (Stuttgart, Germany)》1994,107(4):201-209
The effects of solubilization with Triton X-100 or Brij 58 on the polypeptide composition and the substrate affinity of the tonoplast H+-ATPase of plants of Mesembryanthemum crystallinum performing C3 photosynthesis or crassulacean acid metabolism (CAM) have been compared. Although all known subunits of the tonoplast H+-ATPase were present in the fraction of solubilized proteins after treatment with Brij 58 or Triton X-100, with Triton X-100 the apparent KM value for ATP hydrolysis was increased by a factor of 1.8 and 1.5 in preparations from C3 and CAM plants, respectively, even at low concentrations in contrast to treatment with Brij 58. This is explained by structural changes of the tonoplast H+-ATPase due to the Triton X-100 treatment. After solubilization with Brij 58 the tonoplast H+-ATPase was partially purified by Superose-6 size-exclusion FPLC. When Brij 58 was present, addition of lipids to the chromatography buffer was not necessary to conserve enzyme activity in contrast to previously described purification methods using Triton X-100. The substrate affinity of the partial purified H+-ATPase was similar to the substrate affinity obtained for ATP-hydrolysis of native tonoplast vesicles, indicating that the enzyme structure during partial purification was conserved by using Brij 58. The results underline that the lipid environment of the tonoplast H+-ATPase is important for enzyme structure and function. 相似文献
11.
Uptake of sucrose into vacuoles of suspension cells of Saccharum sp. (sugarcane) was investigated using a vacuole-isolation method based on osmotic- and pH-dependent lysis of protoplasts. Vacuoles took up sucrose at high rates without the influence of tonoplast energization on sucrose transport. Neither addition of ATP or pyrophosphate nor dissipation of the membrane potential or the pH gradient by ionophores changed uptake rates appreciably. Generation of an ATP-dependent pH gradient across the tonoplast was measured in vacuoles and tonoplast vesicles by fluorescence quenching of quinacrine. No H+ efflux could be measured by addition of sucrose to energized vacuoles or vesicles so that there was no evidence for a sucrose/H+ antiport system. Uptake rates of glucose and other sugars were similar to those of sucrose indicating a relatively non-specific sugar uptake into the vacuoles. Sucrose uptake was concentration-dependent, but no clear saturation kinetics were found. Strict dependence on medium pH and inhibition of sucrose transport by p-chloromercuriphenylsulfonic acid (PCMBS) indicate that sucrose uptake into sugarcane vacuoles is a passive, carrier-mediated process.Abbreviations FCCP
carbonylcyanide-p-trifluoromethoxyphenylhydrazone
- Mes
2-(N-morpholino)ethanesulfonic acid
- Mops
3-(N-morpholino)propanesulfonic acid
- PCMBS
p-chloromercuriphenylsulfonic acid
- PPi
pyrophosphate
This research was supported by the Deutsche Forschungsgemeinschaft. The technical assistance of H. Schroer is gratefully acknowledged. 相似文献
12.
Kripkyy Oleg Kerkeb Loubna Molina Anabel Belver Andrés Rodríguez-Rosales Pilar Donaire Juan Pedro 《Plant Cell, Tissue and Organ Culture》2001,66(1):41-47
The effects of NaCl-adaptation and NaCl-stress on in vivo H+ extrusion and microsomal vanadate- and bafilomycin-sensitive ATPase and PPase activities were studied in tomato cell suspensions.
Acidification of the external medium by 50 mM NaCl-adapted and non-adapted (control) tomato cells was similar. Extracellular
acidification by both types of cells during the first hour of incubation with 2 μM fusicoccin (FC) in the presence of 100
mM NaCl was lightly increased while in the presence of 100 mM KCl it was increased by 3 (control)- and 6.5 (adapted)-fold.
Extracellular alkalinization after 2 h of cell incubation in 100 mM NaCl indicated the possibility that a Na+/H+ exchange activity could be operating in both types of cells. Moreover, acidification induced by adding 100 mM NaCl + FC to
non-adapted cells was relatively less affected by vanadate than that induced by 5 mM KCl + FC, which suggested that salt stress
could induce some component other than H+ extrusion by H+-ATPase. In addition, no differences were observed in microsomal vanadate-sensitive ATPase activity among control, NaCl-adapted
and NaCl-stressed cells, while K+-stimulated H+-PPase and bafilomycin-sensitive H+-ATPase activities were higher in microsomes from NaCl-adapted than in those from control cells. Likewise, the stimulation
of in vivo H+ extrusion in NaCl adapted cells under NaCl or KCl stress in the presence of FC occurred with an inhibition of H+-PPase and bafilomycin-sensitive H+-ATPase activities and without changes in the vanadate-sensitive H+-ATPase activity. These results suggest that the stimulation of tonoplast proton pumps in NaCl-adapted cells, without changes
in plasmalemma H+-ATPase, could serve to energize Na+ efflux across the plasmalemma and Na+ fluxes into vacuoles catalyzed by the Na+/H+ antiports.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
14.
15.
Plants of the facultative halophyte and CAM species Mesembryanthemum crystallinum L. (Aizoaceae) were stressed for 8 d with 400 mol m−3 NaCl in the root medium. NaCl was then removed from the substratum, and the plants were watered again with NaCl-free solution. A second set of plants was maintained as controls. A small degree of CAM, as indicated by day-night changes in malate levels, was expressed during ageing of the plants. Salinity-stress-dependent CAM induction was reversible by the removal of salt, as indicated by similar Δ malate levels in previously salt-stressed plants and in non-stressed plants on day 19 of the experiment. Tonoplast vesicles were isolated from leaves during the time-course of stress application, stress removal and ageing. Parameters of the tonoplast H+-ATPase were correlated to the application of salinity, the expression of CAM and ageing. It was concluded, first, that a pronounced increase in the amount of tonoplast H+-ATPase is related to salinity per se and a smaller increase to ageing; secondly, that there is an increase in the specific activity of the enzyme related to ageing; thirdly, that the induction of two new polypeptides with molecular masses of 32 and 28 kDa is correlated in time with the expression of CAM, and, fourthly, that the two new polypeptides are part of the tonoplast H+-ATPase holoenzyme. 相似文献
16.
17.
Molecular Cloning and Different Expression of a Vacuolar Na+/H+ antiporter gene in Suaeda salsa Under Salt Stress 总被引:3,自引:0,他引:3
X.-L. Ma Q. Zhang H.-Z. Shi J.-K. Zhu Y.-X. Zhao C.-L. Ma H. Zhang 《Biologia Plantarum》2004,48(2):219-225
A Na+/H+ antiporter catalyzes the transport of Na+ and H+ across the tonoplast membrane. We isolated a vacuolar Na+/H+ antiporter cDNA (SsNHX1) clone from a euhalophyte, Suaeda salsa. The nuclear sequence contains 2262 bp with an open reading frame of 1665 bp. The deduced amino acid sequence is similar
to that of AtNHX1 and OsNHX1 in rice, with the highest similarities within the predicted transmembrane segments and an amiloride-binding domain. Northern
blot analysis shows that the expression of the S. salsa gene was increased by salt stress. The results suggest that the SsNHX1 product is likely a Na+/H+ antiporter and may play important roles in the salt tolerance of S. salsa.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Co‐expression of tonoplast Cation/H+ antiporter and H+‐pyrophosphatase from xerophyte Zygophyllum xanthoxylum improves alfalfa plant growth under salinity,drought and field conditions
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Salinity and drought are major environmental factors limiting the growth and productivity of alfalfa worldwide as this economically important legume forage is sensitive to these kinds of abiotic stress. In this study, transgenic alfalfa lines expressing both tonoplast NXH and H+‐PPase genes, ZxNHX and ZxVP1‐1 from the xerophyte Zygophyllum xanthoxylum L., were produced via Agrobacterium tumefaciens‐mediated transformation. Compared with wild‐type (WT) plants, transgenic alfalfa plants co‐expressing ZxNHX and ZxVP1‐1 grew better with greater plant height and dry mass under normal or stress conditions (NaCl or water‐deficit) in the greenhouse. The growth performance of transgenic alfalfa plants was associated with more Na+, K+ and Ca2+ accumulation in leaves and roots, as a result of co‐expression of ZxNHX and ZxVP1‐1. Cation accumulation contributed to maintaining intracellular ions homoeostasis and osmoregulation of plants and thus conferred higher leaf relative water content and greater photosynthesis capacity in transgenic plants compared to WT when subjected to NaCl or water‐deficit stress. Furthermore, the transgenic alfalfa co‐expressing ZxNHX and ZxVP1‐1 also grew faster than WT plants under field conditions, and most importantly, exhibited enhanced photosynthesis capacity by maintaining higher net photosynthetic rate, stomatal conductance, and water‐use efficiency than WT plants. Our results indicate that co‐expression of tonoplast NHX and H+‐PPase genes from a xerophyte significantly improved the growth of alfalfa, and enhanced its tolerance to high salinity and drought. This study laid a solid basis for reclaiming and restoring saline and arid marginal lands as well as improving forage yield in northern China. 相似文献
19.
Assessment of glycinebetaine and proline compartmentation by analysis of isolated beet vacuoles 总被引:2,自引:0,他引:2
Vacuoles isolated from storage root tissue of red beet (Beta vulgaris L.) do not leak significant quantities of betanin, sucrose, Na+ or K+ during isolation. This indicates that analysis of vacuoles in vitro gives meanigful information about the compartmentation of solutes in vivo. Preparations of vacouoles were used to determine the distribution of glycinebetaine and proline between vacuole and cytoplasm in beet cells. Both compounds were detected in preparations of isolated beet vacuoles. In the case of glycinebetaine it was shown that this solute was associated with the vacuoles, not with the small number of other organelles which contaminated the preparations. The vacuolar pool accounted for 26 to 84% of the total tissue glycinebetaine and 17 to 57% of the proline. Concentrations of these compounds in vacuole and cytoplasm were calculated and were always higher in the cytoplasm than in the vacuole. The concentration gradient across the tonoplast varied considerably. The significance of these results is discussed in relation to the hypothesis that glycinebetaine and proline function as benign cytoplasmic osmotica.Abbreviations A537
absorbance at 537 nm
- MES
2-(N-morpholino)-ethanesulphonic acid
- Na2EDTA
ethylenediaminetetraacetic acid, disodium salt
- SDS
sodium dodecyl sulphate
- Tris
tris(hydroxymethyl)methylamine 相似文献
20.
Chang-Quan Wang Cheng Xu Ji-Guo Wei Hong-Bo Wang Shao-Hai Wang 《Journal of Plant Growth Regulation》2008,27(1):58-67
In this study, high-betacyanin Suaeda salsa seedlings were developed and used to explore whether the betacyanin accumulation is related to salinity tolerance in S. salsa. After 8 days of culture, betacyanin content decreased markedly in both high-betacyanin S. salsa seedlings and the control under nonsalt stress, but the decreases were suppressed by NaCl treatments. Betacyanin content
in high-betacyanin seedlings was much higher than that in the control throughout the salt treatments. Growth of S. salsa plants was significantly promoted by NaCl treatments, and the fresh weight of high-betacyanin seedlings was much higher than
that of the control when grown in 400 mmol L−1 NaCl. Similar cell sap osmolarity and K+/Na+ ratios were observed in high-betacyanin seedlings and the control. No obvious differences in V-ATPase (tonoplast H+-ATPase) activity, leaf SOD (superoxide dismutase) activity, and total chloroplast SOD (including thylakoid-bound SOD and
stroma SOD) activity were detected between high-betacyanin seedlings and the control under nonsalt stress conditions. However,
V-ATPase hydrolytic activity increased dramatically in S. salsa seedlings when subjected to different levels of NaCl, and the increases in V-ATPase activity in high-betacyanin seedlings
were much higher than that in the control. No clear pattern was observed for NaCl-dependent activity changes of P-ATPase (plasma
membrane H+-ATPase) and V-PPase (tonoplast H+-pyrophosphatase). Similar changes were demonstrated in leaf SOD activity and chloroplast SOD activity under salt stress.
Both leaf SOD activity and chloroplast SOD activity were markedly enhanced with the increase of NaCl or with time, especially
thylakoid-bound SOD activity. Furthermore, the increases in chloroplast SOD activity and thylakoid-bound SOD activity were
much higher in high-betacyanin seedlings than that in the control at different levels of NaCl treatment. The higher V-ATPase
activity, chloroplastic SOD activity, and thylakoid-bound SOD activity demonstrated in high-betacyanin seedlings, but lower
in the control, suggest that high-betacyanin S. salsa seedlings may have higher potential to be energized by the electrochemical gradient for ion uptake into the vacuole and to
scavenge O2−• in situ produced in the chloroplasts, which may lead to higher salt tolerance than the control under salt stress. Thus, betacyanin
may be involved in salt tolerance of S. salsa. 相似文献