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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Chenopodiaceae Suaeda salsa L. was grown under different salt concentrations and under osmotic stress. The fresh weight was markedly stimulated by 0.1 M NaCl, 0.4 M NaCl and 0.1 M KCl and reduced by osmotic stress (PEG iso-osmotic to 0.1 M NaCl). Treatment with 0.4 M KCl severely damaged the plants. Membrane vesicle fractions containing tonoplast vesicles were isolated by sucrose gradient from leaves of the S. salsa plants and modulations of V-ATPase and V-PPase depending on the growth conditions were determined. Western blot analysis revealed that V-ATPase of S. salsa consists of at least nine subunits (apparent molecular masses 66, 55, 52, 48, 36, 35, 29, 18, and 16 kDa). This polypeptide pattern did not depend on culture conditions. V-PPase is composed of a single polypeptide (69 kDa). An additional polypeptide (54 kDa) was detected in the fractions of NaCl-, KCl- and PEG-treated plants. It turned out that the main strategy of salt-tolerance of S. salsa seems to be an up-regulation of V-ATPase activity, which is required to energize the tonoplast for ion uptake into the vacuole, while V-PPase plays only a minor role. The increase in V-ATPase activity is not obtained by structural changes of the enzyme, but by an increase in V-ATPase protein amount.
J Exp Bot 2001 Dec
PMID:Effects of salt treatment and osmotic stress on V-ATPase and V-PPase in leaves of the halophyte Suaeda salsa. 1170 85

The hydrolysis of ATP(4-) by the plasmalemma and tonoplast H(+)/ATPases and by the tonoplast pyrophosphatase results in the export of a proton to the apoplast or vacuole with remaining in the cytoplasm. As the enzymes that synthesize ATP(4-) require as a substrate it is proposed that protons are an essential substrate for ATP(4-) synthesis. Thus, the entry of protons to the cytoplasm by sym- and antiports will control the rate of ATP(4-) synthesis. Evidence is adduced that plants control the tension on the water column by removing water to or from the 'cellular reservoir' and guard cells by generating osmotic gradients. Schemes are presented that propose a series of metabolic changes that result in a seamless transition through the following states: (1) the import of K(+), Cl(-) and water from the apoplast to the vacuole, the K(+) being admitted to the cytoplasm via a Ca(2+)-activated K(+)-H(+) symport and the water via a Ca(2+)-activated aquaporin; (2) the continued import of K(+) and water from the apoplast to the vacuole with the concomitant export of protons and the synthesis of malate from glucose in the cytoplasm for importation into the vacuole; (3) when the tension on the water column is optimal, respiration and photosynthesis is maximal resulting in biosynthetic reactions and growth; (4) when tension on the water column increases, K(+), Cl(-) and water are exported from the vacuole to the apoplast; (5) the continued export of K(+) and water from the vacuole to the apoplast with malate for export being synthesized in the cytoplasm; the export of K(+) resulting in the acidification of the vacuole; and (6) a further increase in tension results in the deactivation of the plasmalemma H(+)/ATPase by a further increase in cytoplasmic Ca(2+) which also indirectly activates the alternative oxidase. It is suggested that mitochondrial pyruvate is partly oxidized by the TCA cycle and is partly exported to the cytoplasm where it is carboxylated to form malate(1-) for continued export to the apoplast. K(+) is transferred from the vacuole to the apoplast, the K(+) being replaced by protons from the export of mitochondrial pyruvate. The maintenance of the tonoplast electrochemical gradient is thought to result in an increase in the pH of the apoplast which may cause the hydrolysis of abscisic acid precursors with the resulting abscisic acid opening Ca(2+) channels so that the above events are reinforced. (7) This mode is proposed to continue by the metabolism of glucose to four phosphoenolpyruvate, three of which are carboxylated to malate(1-) for continued export to the apoplast with K(+) from the vacuole, the 'stress-tolerant quiescent state'.
J Exp Bot 2002 Feb
PMID:pH, abscisic acid and the integration of metabolism in plants under stressed and non-stressed conditions. II. Modifications in modes of metabolism induced by variation in the tension on the water column and by stress. 1180 19

Tortula ruralis is an important experimental system for the study of plant vegetative desiccation tolerance. EST gene discovery efforts utilizing desiccated gametophytes have identified a cDNA Vac1 encoding a predicted polypeptide with significant similarity to the vacuolar H(+)-ATPase c subunit. VAC1, the 167 amino acid deduced polypeptide, has a predicted molecular mass of 16.9 kDa, and a predicted pI of 9.7. Phylogenetic analysis demonstrated that previously characterized proteolipid polypeptide sequences could be reproducibly grouped into two major clades and that VAC1 forms a discrete evolutionary group. RNA blot and Western blot hybridizations were used to analyse expression of Vac1 and accumulation of VAC1 in response to (1) desiccation and rehydration, (2) increased NaCl concentration, and (3) NaCl-shock. During a desiccation-rehydration cycle, Vac1 transcripts are expressed in both the total and polysomal RNA fractions in approximately equal amounts, and the steady-state transcript levels are unchanged. However, Vac1 transcript levels increased in response to both elevated NaCl concentration and NaCl-shock. There is a preferential accumulation of Vac1 transcripts within the polysomal RNA fraction in response to salt stress, and these data suggest that T. ruralis possesses a salinity-stress-dependent and desiccation-stress-independent mechanism for post-transcriptional gene control. Using a cotton anti-c subunit polyclonal antibody raised against the C-terminal domain, it was shown that the amount of Tortula 16 kDa proteolipid in the tonoplast protein fraction was unaffected by any stress treatment.
J Exp Bot 2002 Feb
PMID:Characterization of the V-type H((+))-ATPase in the resurrection plant Tortula ruralis: accumulation and polysomal recruitment of the proteolipid c subunit in response to salt-stress. 1180 26

Unmodified samples of barley (Hordeum vulgare) sieve tube sap have been obtained by severing the stylets (stylectomy) of feeding aphids and collecting the exuding liquid. Primers were designed to direct the amplification of a series of specific cDNAs encoding barley proteins selected because of their significance in sieve tube function. mRNA encoding the H(+)/sucrose co-transporter SUT1, a putative aquaporin and the H(+)/ATPase PPA1 were detected in sieve tube sap. These mRNA species appear to be present at very low concentrations. mRNA encoding the potassium transporter HAK1 could not be detected. The results strongly suggest that some mRNA species are imported into sieve elements, which are enucleate, from neighbouring companion cells.
J Exp Bot 2002 Apr
PMID:Use of aphid stylectomy and RT-PCR for the detection of transporter mRNAs in sieve elements. 1188 82

Regulation by arbuscular mycorrhizal symbiosis of three tomato plasma membrane H+-ATPase genes (LHA1, LHA2 and LHA4) has been analysed in wild-type and mycorrhiza-defective tomato plants. Expression of these genes was differentially regulated in leaves and roots of both tomato phenotypes after inoculation with Glomus mosseae.
J Exp Bot 2002 Jul
PMID:Arbuscular mycorrhizal symbiosis regulates plasma membrane H+-ATPase gene expression in tomato plants. 1209 8

It is generally understood that the inhibition of growth of root apices is the initial effect caused by aluminium (Al) toxicity. The correlation between impaired H+-fluxes across the plasma membrane (PM) and Al-induced growth inhibition, Al accumulation and callose formation in root apices of squash (Cucurbita pepo L. cv. Tetsukabuto) is reported here. The root inhibition was dependent on Al concentration, and the duration of exposure, with the damage occurring preferentially in regions with high Al accumulation and callose formation. Using the fluorescent Al indicator (Morin), Al was localized in the cell walls of the root-tip cells after 3 h and in the whole root-tip cells after 6 h of the Al treatment (50 micro M). The inhibition of H+-pumping rate in the highly purified PM vesicles obtained from the Al-treated apical root portions (1 cm) coincided with the inhibition of root growth under Al stress. Furthermore, H+-ATPase activity of PM vesicles prepared from the control root apices was strongly inhibited by Al in vitro in a dose-dependent manner. Approximately 50% inhibition was observed when PM vesicles were preincubated at Al concentration as low as 10 micro M followed by the enzyme assay in the medium without Al. Using the pH indicator (bromocresol purple), it is shown that surface pH of the control (0 Al) root apices was strongly alkalized from the starting pH of 4.5 in a time-dependent manner. By contrast, the surface pH changed only slightly in the Al-treated root apices. The changes in surface pH mediated by altered dynamics of H+ efflux and influx across the root tip PM play an important role in root growth as affected by Al.
J Exp Bot 2002 Sep
PMID:Aluminium-induced growth inhibition is associated with impaired efflux and influx of H+ across the plasma membrane in root apices of squash (Cucurbita pepo). 1217 36

The maintenance of root elongation is an important adaptive response to low water potentials (psi(w)), but little is known about its regulation. An important component may be changes in root cell electrophysiology, which both signal and maintain growth maintenance processes. As a first test of this hypothesis, membrane potentials (E(m)) were measured within the cell elongation zone of maize (Zea mays L.) primary roots. Seedlings were grown in oxygenated solution culture, and low psi(w) was imposed by the gradual addition of polyethylene glycol. Cells hyperpolarized approximately 25 mV in response to low psi(w), and after 48 h resting potentials remained significantly hyperpolarized at psi(w) lower than -0.3 MPa compared with roots at high psi(w). Inhibitor experiments showed that the hyperpolarization was dependent on plasma membrane H(+)-ATPase activity. Previous work showed that accumulation of abscisic acid (ABA) is required for the maintenance of maize primary root elongation at low psi(w). To determine if the mechanism of action of ABA involves changes in root electrophysiology, E(m) measurements were made during long-term exposure to low psi(w). Steady-state resting E(m) were measured in regions in which maintenance of cell elongation was dependent on ABA accumulation (2-3 mm from the apex), or in which elongation was inhibited regardless of ABA status (6-8 mm from the apex). E(m) was substantially more negative in ABA-deficient roots specifically in the 2-3 mm region. The results suggest that set-points for ion homeostasis shifted in association with the maintenance of root cell elongation at low psi(w), and that ABA accumulation plays a role in regulating the ion transport processes involved in this response.
J Exp Bot 2003 Feb
PMID:Electrophysiological responses of maize roots to low water potentials: relationship to growth and ABA accumulation. 1255 24

Two maize genotypes differently responsive to nitrogen availability were characterized for their efficiency in nitrate accumulation via both the LATS (Low-Affinity Transport System) and HATS (High-Affinity Transport System) nitrate uptake systems. In addition, a full-length cDNA encoding a putative high-affinity nitrate transporter (ZmNrt2.1) was isolated and its expression evaluated in both the roots and leaves of the two maize genotypes, together with the expression of a maize H(+)-ATPase isoform (Mha1). The data showed the importance of the iHATS (Inducible High-Affinity System) system efficiency as a physiological marker of adaptation to low input and suggested that the transcript accumulation of ZmNrt2.1 might be a key step for the regulation of iHATS. However, ZmNrt2.1 transcription cannot account for the differences found between the two hybrids in terms of the activity of their respective iHATS and, as a consequence, of their adaptation to low input. Therefore, the involvement of some other transporter(s) or of some post-transcriptional/post-translational mechanism of regulation affecting the efficiency of iHATS may be hypothesized. In addition, the data suggest that the transcription of the Mha1 gene may also be involved in the global efficiency of the iHATS system.
J Exp Bot 2003 Mar
PMID:Expression of a putative high-affinity NO3- transporter and of an H+-ATPase in relation to whole plant nitrate transport physiology in two maize genotypes differently responsive to low nitrogen availability. 1259 72

An investigation was carried out to assess the effect of nitrate supply on the root plasma membrane (PM) H+-ATPase of etiolated maize (Zea mays L.) seedlings grown in hydroponics. The treatment induced higher uptake rates of the anion and the expression of a putative high-affinity nitrate transporter gene (ZmNRT2.1), the first to be identified in maize. Root PM H+-ATPase activity displayed a similar time-course pattern as that of net nitrate uptake and investigations were carried out to determine which of the two isoforms reported to date in maize, MHA1 and 2, responded to the treatment. MHA1 was not expressed under the conditions analysed. Genome analysis revealed that MHA2, described as the most abundant form in all maize tissues, was not present in the maize hybrid investigated, but a similar form was found instead and named MHA3. A second gene (named MHA4) was also identified and partially sequenced. Both genes, classified as members of the PM H+-ATPase subfamily II, responded to nitrate supply, although to different degrees: MHA4, in particular, proved more sensitive than MHA3, with a greater up- and down-regulation in response to the treatment. Increased expression of subfamily II genes resulted in higher steady-state levels of the enzyme in the root tissues and enhanced ATP-hydrolysing activity. The results support the idea that greater proton-pumping activity is required when nitrate inflow increases and suggest that nitrate may be the signal triggering the expression of the two members of PM H+-ATPase subfamily II.
J Exp Bot 2003 Aug
PMID:Induction of nitrate uptake in maize roots: expression of a putative high-affinity nitrate transporter and plasma membrane H+-ATPase isoforms. 1286 20

Wheat root tips express a 73 kDa cognate isoform and a 77 kDa heat-shock-induced isoform of peptidyl prolyl cis-trans isomerase (FK506 binding protein; FKBP) that is part of a chaperone complex with hsp90. The 73 kDa and 77 kDa FKBPs have very similar sequences, differing primarily in the N- and C-terminal 20 amino acids. In order to define the potential functional roles of these proteins, the 73 kDa and 77 kDa FKBPs were localized in root tips using antigen-affinity purified antibodies as a probe. The cognate 73 kDa FKBP is localized in the cytoplasm and appears enriched around the periphery of the early vacuole and vesicles exiting the trans-Golgi. Parallel assays with antibodies directed against tonoplast aquaporin and pyrophosphatase confirmed the association of FKBP with an early vacuole compartment. Sucrose gradient centrifugation analysis of root tip lysates also showed that 73 kDa FKBP is co-fractionated with tonoplast aquaporin and V-ATPase in a light compartment near the top of the gradient. Heat-shock treatment of root tips induces the accumulation of 77 kDa FKBP while the abundance of 73 kDa FKBP remains constant. Quantitative EM immunogold assays of the intracellular distribution of FKBP over an 8 h heat-shock time-course showed that FKBP is initially present in the cytoplasm, but is transported into the nucleus where it accumulates in the nucleoplasm and into specific subnuclear domains. The results of this study show that the intracellular distribution of the high Mr FKBPs in wheat root tips differs at normal and elevated temperatures, indicating different functional roles for the FKBP isoforms.
J Exp Bot 2003 Dec
PMID:Differential distribution of the cognate and heat-stress-induced isoforms of high Mr cis-trans prolyl peptidyl isomerase (FKBP) in the cytoplasm and nucleoplasm. 1458 27


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