Alkalinization

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Christoph-martin Geilfus - One of the best experts on this subject based on the ideXlab platform.

  • the ph of the leaf apoplast is critical for the formation of pseudomonas syringae induced lesions on leaves of the common bean phaseolus vulgaris
    Plant Science, 2020
    Co-Authors: Christoph-martin Geilfus, Li Wang, Jiawen Wu
    Abstract:

    Abstract Inoculating a virulent strain of Pseudomonas syringae pv. phaseolicola (Pph) into the leaf of common bean (Phaseolus vulgaris) causes the leaf apoplast to alkalinize. Whether or not this apoplastic pH event facilitates virulence of Pph in interaction with common bean is unclear. For elucidating this topic, (i) Pph colonization of the common bean leaf apoplast, (ii) the formation of bacterial lesions, and (iii) apoplastic sucrose concentration were investigated in relation to the apoplastic leaf pH. For this, the Pph-induced leaf apoplastic Alkalinization was attenuated by spray application of either a synthetic auxin or an acidic pH buffer. Apoplastic pH was quantified in planta via microscopy-based pH imaging. Apoplastic washing fluids were extracted to quantify both colonization of bacteria in leaf apoplast and the concentration of apoplastic sucrose. Results reveal that the apoplastic Alkalinization facilitated bacterial colonization of the apoplast. Number of colony forming units and area of bacterial lesions were reduced when Pph-induced apoplastic Alkalinization was attenuated by foliar application of a synthetic auxin or acidic pH buffer. Application of both agents attenuated the Pph-induced increase of sucrose in the leaf apoplast, which is nutrient for bacteria. Data demonstrate that the Pph-mediated leaf apoplastic alkalinisation favours bacterial colonization.

  • transient Alkalinization of the leaf apoplast stiffens the cell wall during onset of chloride salinity in corn leaves
    Journal of Biological Chemistry, 2017
    Co-Authors: Christoph-martin Geilfus, Raimund Tenhaken, Sebastien Carpentier
    Abstract:

    Abstract During chloride salinity, the pH of the leaf apoplast (pHapo) transiently alkalizes. There is an ongoing debate about the physiological relevance of these stress-induced pHapo changes. Using proteomic analyses of expanding leaves of corn (Zea mays L.), we show that this transition in pHapo conveys functionality by (i) adjusting protein abundances and (ii) affecting the rheological properties of the cell wall. pHapo was monitored in planta via microscopy-based ratio imaging, and the leaf-proteomic response to the transient leaf apoplastic Alkalinization was analyzed via ultra-high performance liquid chromatography–MS. This analysis identified 1459 proteins, of which 44 exhibited increased abundance specifically through the chloride-induced transient rise in pHapo. These elevated protein abundances did not directly arise from high tissue concentrations of Cl− or Na+ but were due to changes in the pHapo. Most of these proteins functioned in growth-relevant processes and in the synthesis of cell wall–building components such as arabinose. Measurements with a linear-variable differential transducer revealed that the transient Alkalinization rigidified (i.e. stiffened) the cell wall during the onset of chloride salinity. A decrease in t-coumaric and t-ferulic acids indicates that the wall stiffening arises from cross-linkage to cell wall polymers. We conclude that the pH of the apoplast represents a dynamic factor that is mechanistically coupled to cellular responses to chloride stress. By hardening the wall, the increased pH abrogates wall loosening required for cell expansion and growth. We conclude that the transient Alkalinization of the leaf apoplast is related to salinity-induced growth reduction.

  • the ph of the apoplast dynamic factor with functional impact under stress
    Molecular Plant, 2017
    Co-Authors: Christoph-martin Geilfus
    Abstract:

    Abstract The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or proton-pump regulations. On the other hand, there are increasing indications that it is part of a mechanism to withstand stress. Regardless of this controversy, Alkalinization of the apoplast has received little attention. The apoplastic pH (pH apo ) increases not only during plant–pathogen interactions but also in response to salinity or drought. Not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor whether, and if so, how functional impact is conveyed. Controversial explanations have been given, and the unusual complexity of pH apo regulation is considered as the primary reason behind this lack of knowledge. A gathering of scattered information revealed that changes in pH apo convey functionality by regulating stomatal aperture via the effects exerted on abscisic acid. Moreover, apoplastic Alkalinization may regulate growth under stress, whereas this needs to be verified. In this review, a comprehensive survey about several physiological mechanisms that alkalize the apoplast under stress is given, and the suitability of apoplastic Alkalinization as transducing element for the transmission of sensory information is discussed.

  • chloride inducible transient apoplastic Alkalinizations induce stomata closure by controlling abscisic acid distribution between leaf apoplast and guard cells in salt stressed vicia faba
    New Phytologist, 2015
    Co-Authors: Christoph-martin Geilfus, Axel Mithofer, Jutta Ludwigmuller, Christian Zörb, Karl Hermann Muehling
    Abstract:

    Summary Chloride stress causes the leaf apoplast transiently to alkalize, an event that is presumed to contribute to the ability of plants to adapt to saline conditions. However, the initiation of coordinated processes downstream of the Alkalinization is unknown. We hypothesize that chloride-inducible pH dynamics are a key chemical feature modulating the compartmental distribution of abscisic acid (ABA) and, as a consequence, affecting stomata aperture. Apoplastic pH and stomata aperture dynamics in intact Vicia faba leaves were monitored by microscopy-based ratio imaging and porometric measurements of stomatal conductance. ABA concentrations in leaf apoplast and guard cells were compared with pH dynamics by gas-chromatography-mass-spectrometry (GC-MS) and liquid-chromatography–tandem-mass spectrometry (LC-MS/MS). Results demonstrate that, upon chloride addition to roots, an alkalizing factor that initiates the pH dynamic propagates from root to leaf in a way similar to xylem-distributed water. In leaves, it induces a systemic transient apoplastic Alkalinization that causes apoplastic ABA concentration to increase, followed by an elevation of endogenous guard cell ABA. We conclude that the transient Alkalinization, which is a remote effect of chloride stress, modulates the compartmental distribution of ABA between the leaf apoplast and the guard cells and, in this way, is instrumental in inducing stomata closure during the beginning of salinity.

  • ratiometric monitoring of transient apoplastic Alkalinizations in the leaf apoplast of living vicia faba plants chloride primes and pm h atpase shapes nacl induced systemic Alkalinizations
    New Phytologist, 2013
    Co-Authors: Christoph-martin Geilfus, Karlhermann Muhling
    Abstract:

    Summary Transient apoplastic Alkalinization has been discussed as a general stress factor, and is thought to represent a root-to-shoot signal that transmits information regarding an ongoing NaCl stress event from the site of the trigger to the distant plant tissue. Surprisingly, despite this importance, a number of gaps exist in our knowledge of NaCl-induced apoplastic pH Alkalinization. This study was designed in order to shed light onto the mechanisms responsible for the initiation and transiency of leaf apoplastic Alkalinization under conditions of NaCl stress as supplied to roots. An H+-sensitive fluorescence probe, in combination with ratiometric microscopy imaging, was used for in planta live recording of leaf apoplastic pH. The use of a nonionic solute demonstrated that the Alkalinization is induced in response to ionic, and not osmotic, components of NaCl stress. Tests with Cl−- or Na+-accompanying counter-ions strengthened the idea that the stress factor itself, namely Cl−, is transferred from root to shoot and elicits the pH alterations. Investigations with a plasma membrane ATPase inhibitor suggest that ATPase activity influences the course of the Alkalinization by having a shaping re-acidifying effect on the Alkalinization.

Pedro J Aparicio - One of the best experts on this subject based on the ideXlab platform.

  • blue light requirement for hc03 uptake and its action spectrum in monoraphidium braunii
    Photochemistry and Photobiology, 1998
    Co-Authors: Nuria Giraldez, Pedro J Aparicio, Miguel Angel Quinones
    Abstract:

    The uptake and assimilation of HCO3 by the green unicellular alga Monoraphidium braunii can be monitored by the Alkalinization of the external medium or by the O2 evolution associated with the uptake and reduction of this anion. The activation of HCO3 uptake in this microalga required the irradiation of the cell suspensions with low photon fluence rates of short wavelength radiation. Thus, when the cells were irradiated with strong red light in the presence of HCO3, very little Alkalinization of the external medium or O2 evolution could be observed. The O2 evolution rates measured under red light could be due to the assimilation of the CO2 derived from the HCO3 present in the medium. The blue light-dependent O2 evolution rates were not diminished by a periplasmic carbonic anhydrase inhibitor, suggesting that HCO3 -dependent O2 evolution was due to the photoactivation of a selective HCO3 uptake system at the plasma membrane. The action spectrum for HCO3- uptake in M. braunii was very similar to those reported for NO3- and CI- suggested that a flavoprotein may be the photoreceptor for this response.

  • effects of short pulses of blue light on the Alkalinization associated with the uptake of no3 and cl by the green alga monoraphidium braunii and related action spectra
    Photochemistry and Photobiology, 1995
    Co-Authors: Federico G Witt, Pedro J Aparicio
    Abstract:

    In Monoraphidium braunii, uptake of NO3−, NO2− and Cl− is associated with proton transport and triggered by blue light (BL). Only 10 s after cells able to reduce NO3− to NH4+ were irradiated with continuous, low-fluence BL in the presence of NO3−, an Alkalinization of the medium began and only became interrupted by switching off the BL with a 60–90 s time lag. With 30 s BL pulses, the NO3−-dependent Alkalinization lasted 3–5 min until it stopped. When the cells were exposed to continuous BL in the presence of Cl−, the Alkalinization also started within 10 s but lasted only 3 min. After that, the pH remained constant and decreased when the BL was switched off. With 30 s BL pulses, the Cl−-dependent Alkalinization lasted 3 min and then decreased to its initial value. The NO3−-dependent Alkalinization shown by cells unable to reduce NO3− to NH4+ was similar to that observed in the presence of Cl−. These Alkalinization rates fit the Bunsen-Roscoe reciprocity law. With 2 s pulses of high-fluence BL, the delay time of the NO3 - or Cl−-dependent Alkalinizations was only 2 s, one of the fastest BL responses reported so far. The action spectra for Cl− and NO3− uptakes proved to be very similar and matched the absorption spectra of flavins, including the 267 nm peak.

  • EFFECTS OF SHORT PULSES OF BLUE LIGHT ON THE Alkalinization ASSOCIATED WITH THE UPTAKE OF NO3− AND CL− BY THE GREEN ALGA MONORAPHIDIUM BRAUNII AND RELATED ACTION SPECTRA
    Photochemistry and Photobiology, 1995
    Co-Authors: Federico G Witt, Pedro J Aparicio
    Abstract:

    In Monoraphidium braunii, uptake of NO3−, NO2− and Cl− is associated with proton transport and triggered by blue light (BL). Only 10 s after cells able to reduce NO3− to NH4+ were irradiated with continuous, low-fluence BL in the presence of NO3−, an Alkalinization of the medium began and only became interrupted by switching off the BL with a 60–90 s time lag. With 30 s BL pulses, the NO3−-dependent Alkalinization lasted 3–5 min until it stopped. When the cells were exposed to continuous BL in the presence of Cl−, the Alkalinization also started within 10 s but lasted only 3 min. After that, the pH remained constant and decreased when the BL was switched off. With 30 s BL pulses, the Cl−-dependent Alkalinization lasted 3 min and then decreased to its initial value. The NO3−-dependent Alkalinization shown by cells unable to reduce NO3− to NH4+ was similar to that observed in the presence of Cl−. These Alkalinization rates fit the Bunsen-Roscoe reciprocity law. With 2 s pulses of high-fluence BL, the delay time of the NO3 - or Cl−-dependent Alkalinizations was only 2 s, one of the fastest BL responses reported so far. The action spectra for Cl− and NO3− uptakes proved to be very similar and matched the absorption spectra of flavins, including the 267 nm peak.

  • blue light induced ph changes associated with no3 no2 and cl uptake by the green alga monoraphidium braunii
    Plant Cell and Environment, 1994
    Co-Authors: Pedro J Aparicio, Miguel Angel Quinones, Federico G Witt, J M Ramirez, T Balandin
    Abstract:

    In M. braunii, the uptake of NO3− and NO2− is blue-light-dependent and is associated with Alkalinization of the medium. In unbuffered cell suspensions irradiated with red light under a CO2-free atmosphere, the pH started to rise 10s after the exposure to blue light. When the cellular NO3− and NO2− reductases were active, the pH increased to values of around 10, since the NH4+ generated was released to the medium. When the blue light was switched off, the pH stopped increasing within 60 to 90s and remained unchanged under background red illumination. Titration with H2SO4 of NO3− or NO2− uptake and reduction showed that two protons were consumed for every one NH4+ released. The uptake of Cl− was also triggered by blue light with a similar 10 s time response. However, the Cl− -dependent Alkalinization ceased after about 3 min of blue light irradiation. When the blue light was turned off, the pH immediately (15 to 30 s) started to decline to the pre-adjusted value, indicating that the protons (and presumably the Cl−) taken up by the cells were released to the medium. When the cells lacked NO3− and NO2− reductases, the shape of the Alkalinization traces in the presence of NO3− and NO2− was similar to that in the presence of Cl−, suggesting that NO3− or NO2− was also released to the medium. Both the NO3− and Cl−-dependent rates of Alkalinization were independent of mono- and divalent cations.

  • Blue-light-induced pH changes associated with NO3−, NO2− and Cl− uptake by the green alga Monoraphidium braunii
    Plant Cell and Environment, 1994
    Co-Authors: Pedro J Aparicio, Miguel Angel Quinones, Federico G Witt, J M Ramirez, T Balandin
    Abstract:

    In M. braunii, the uptake of NO3− and NO2− is blue-light-dependent and is associated with Alkalinization of the medium. In unbuffered cell suspensions irradiated with red light under a CO2-free atmosphere, the pH started to rise 10s after the exposure to blue light. When the cellular NO3− and NO2− reductases were active, the pH increased to values of around 10, since the NH4+ generated was released to the medium. When the blue light was switched off, the pH stopped increasing within 60 to 90s and remained unchanged under background red illumination. Titration with H2SO4 of NO3− or NO2− uptake and reduction showed that two protons were consumed for every one NH4+ released. The uptake of Cl− was also triggered by blue light with a similar 10 s time response. However, the Cl− -dependent Alkalinization ceased after about 3 min of blue light irradiation. When the blue light was turned off, the pH immediately (15 to 30 s) started to decline to the pre-adjusted value, indicating that the protons (and presumably the Cl−) taken up by the cells were released to the medium. When the cells lacked NO3− and NO2− reductases, the shape of the Alkalinization traces in the presence of NO3− and NO2− was similar to that in the presence of Cl−, suggesting that NO3− or NO2− was also released to the medium. Both the NO3− and Cl−-dependent rates of Alkalinization were independent of mono- and divalent cations.

David S. Goldfarb - One of the best experts on this subject based on the ideXlab platform.

  • uric acid stones and hyperuricosuria
    Advances in Chronic Kidney Disease, 2012
    Co-Authors: Tapan H Mehta, David S. Goldfarb
    Abstract:

    Recent work has highlighted the strong relationships among obesity, diabetes, and the metabolic syndrome as causes of low urinary pH. Low urinary pH in turn is the major urinary risk factor for uric acid stones. Unlike calcium stones, uric acid stones can be dissolved and easily prevented with adequate urinary Alkalinization. Recognizing the relevant risk factors should lead to increased identification of these radiolucent stones. The cornerstone of therapy is raising urinary pH; xanthine dehydrogenase inhibitors should be used only when urinary Alkalinization cannot be achieved.

Rachelle Buchbinder - One of the best experts on this subject based on the ideXlab platform.

  • ab0631 efficacy and safety of urine Alkalinization for patients with uric acid nephrolithiasis with or without gout arthritis a systematic review
    Annals of the Rheumatic Diseases, 2013
    Co-Authors: F Teixeira, Joao Rovisco, Sofia Ramiro, J C Branco, Rachelle Buchbinder
    Abstract:

    Background Gout is a complex metabolic and inflammatory disease with varying clinical presentations including gouty arthritis, uric acid nephrolithiasis and renal impairment. Urine Alkalinization may be a useful adjunct in the management of gout. As part of the 3e initiative for generating recommendations for the diagnosis and management of gout, we performed a systematic review using Cochrane methods to determine the efficacy and safety of urine Alkalinization in patients with uric acid nephrolithiasis with or without gouty arthritis. Objectives Determine the efficacy and safety of urine Alkalinization in patients with uric acid nephrolithiasis with or without gouty arthritis. Methods We searched Medline, EMBASE and Cochrane databases to March 2012, and 2010-11 ACR/EULAR abstracts to identify all randomized controlled trials (RCTs) and quasi-RCTs that compared urine Alkalinization to placebo or another therapy in people with uric acid nephrolithiasis with or without gouty arthritis. Primary outcomes were uric acid stone regression and withdrawals due to adverse effects. Two review authors independently selected studies for inclusion, assessed risk of bias (RoB) and extracted data using Cochrane methods. Results A total of 7103 articles were identified, of which 76 articles were selected for detailed review and two fulfilled inclusion criteria. One trial (60 participants) was judged to be at low risk of bias (RoB) and compared potassium citrate to phytotherapy. At 12 weeks, 14/30 (47%) people who received potassium citrate achieved uric acid stone remission compared to 9/30 (30%) in the phytotherapy group (P=0.05). The other trial (191 participants) was judged to be at unclear RoB and compared four treatment arms: potassium citrate and tamsulosin versus placebo or potassium citrate or tamsulosin. At 4 weeks, 27/46 (59%) who received potassium citrate achieved stone remission compared to 12/46 (26%) in the placebo group (P=0.003). There were no withdrawals in either trial due to adverse events. Conclusions There is limited evidence from two trials (1 at low RoB and 1 at unclear RoB) that urine Alkalinization may be an efficacious and safe treatment for patients with uric acid nephrolithiasis with or without gouty arthritis. Disclosure of Interest None Declared

Karl Hermann Muehling - One of the best experts on this subject based on the ideXlab platform.

  • chloride inducible transient apoplastic Alkalinizations induce stomata closure by controlling abscisic acid distribution between leaf apoplast and guard cells in salt stressed vicia faba
    New Phytologist, 2015
    Co-Authors: Christoph-martin Geilfus, Axel Mithofer, Jutta Ludwigmuller, Christian Zörb, Karl Hermann Muehling
    Abstract:

    Summary Chloride stress causes the leaf apoplast transiently to alkalize, an event that is presumed to contribute to the ability of plants to adapt to saline conditions. However, the initiation of coordinated processes downstream of the Alkalinization is unknown. We hypothesize that chloride-inducible pH dynamics are a key chemical feature modulating the compartmental distribution of abscisic acid (ABA) and, as a consequence, affecting stomata aperture. Apoplastic pH and stomata aperture dynamics in intact Vicia faba leaves were monitored by microscopy-based ratio imaging and porometric measurements of stomatal conductance. ABA concentrations in leaf apoplast and guard cells were compared with pH dynamics by gas-chromatography-mass-spectrometry (GC-MS) and liquid-chromatography–tandem-mass spectrometry (LC-MS/MS). Results demonstrate that, upon chloride addition to roots, an alkalizing factor that initiates the pH dynamic propagates from root to leaf in a way similar to xylem-distributed water. In leaves, it induces a systemic transient apoplastic Alkalinization that causes apoplastic ABA concentration to increase, followed by an elevation of endogenous guard cell ABA. We conclude that the transient Alkalinization, which is a remote effect of chloride stress, modulates the compartmental distribution of ABA between the leaf apoplast and the guard cells and, in this way, is instrumental in inducing stomata closure during the beginning of salinity.