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  • 1. Cherian, Sam
    et al.
    Weyens, Niele
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Vangronsveld, Jaco
    Phytoremediation of Trace element Contaminated Environments and the Potential of Endophytic Bacteria for Improving this Process2012In: Critical reviews in environmental science and technology, ISSN 1064-3389, E-ISSN 1547-6537, Vol. 42, no 21, p. 2215-2260Article, review/survey (Refereed)
    Abstract [en]

    Trace elements (heavy metals and metalloids) are among the most widespread contaminants that pose serious threat to all living organisms. Plant and microbial-assisted remediation holds great promise for in situ remediation of trace element contaminated environments. An extended knowledge of plant processes generally involved in the uptake, translocation, storage and detoxification of contaminants, and plant-microbe interactions were essential in developing improved technologies for environmental clean up. Currently, with the initiation of transgenic technologies, great strides have been made in trace element phytoremediation research. In this review, we provide an overview of the current knowledge of how plants cope with trace elements and discuss the development of transgenic plants with improved trace element remediation capabilities. In addition, this review also addresses the recent progress made towards understanding the plant-microbe interactions, especially of endophytic bacteria (natural and genetically engineered), and their contribution in improving the efficiency and versatility of trace element phytoremediation. 

  • 2.
    D'Onofrio, Cladio
    et al.
    University of Pisa, Italy.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Sodium induces simultaneous changes in cytosolic calcium and pH in salt-tolerant quince protoplasts2009In: Journal of plant physiology (Print), ISSN 0176-1617, E-ISSN 1618-1328, Vol. 166, p. 1755-1763Article in journal (Refereed)
    Abstract [en]

    Previousexperimentswithsalt-resistantquinceBA29(Cydonia oblonga cv.Mill.) have shownthatthiscultivartakesupsodiumtransientlyintothecytosolofshoot protoplasts onlyintheabsenceofcalciumchloride,orat o1mMcalciumchloride. Addition ofNaClZ100mMtosingleprotoplastsfrom in vitro-cultivated quinceinthe presence of1.0mMcalciuminducedinstantchangesinthecytosolicconcentrations of calciumandprotons.Thesechangeswereinvestigatedbyuseoftetra [acetoxymethyl] estersofthefluorescentstilbenechromophoresFura2andbis- carboxyethyl-carboxyfluorescein (BCECF),respectively.ThecytosolicCa2+ dynamics in theprotoplastsweredependentontheconcentrationofNaCladded.Thechanges in calciumdifferedinamplitudeandfinalconcentrationandwerecorrelatedintime mainly withchangesinpH.Additionof100–400mMNaCltotheprotoplastscausedan oscillating increaseinthecytosoliclevelofcalcium,andthenadecrease.Addition of mannitol,ofequiosmolarconcentrationtoNaCl,didnotincreasethecytosolic calcium concentration.Moreover,therewasnoincreaseincytosoliccalciumwhen NaCl wasaddedinthepresenceofcalciumbindingethyleneglycol-bis(beta- aminoethylether)-N,N,N0,N0-tetra aceticacid(EGTA),orlantanorverapamil,two inhibitors ofplasmamembranecalciumchannels.Therefore,weconcludethat,in salt-resistant quince,sodiuminducesaninfluxofcalciumintothecytosolbyplasma membrane calciumchannels,andasimultaneousincreaseincytosolicpH.Because these changeswereobtainedinthepresenceof1mMcalciuminthemedium,they were notduetosodiumuptakeintothecytosol.

  • 3.
    Greger, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Kabir, Ahmad H.
    Landberg, Tommy
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Maity, Pooja J.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Silicate reduces cadmium uptake into cells of wheat2016In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 211, p. 90-97Article in journal (Refereed)
    Abstract [en]

    Cadmium (Cd) is a health threat all over the world and high Cd content in wheat causes high Cd intake. Silicon (Si) decreases cadmium content in wheat grains and shoot. This work investigates whether and how silicate (Si) influences cadmium (Cd) uptake at the cellular level in wheat. Wheat seedlings were grown in the presence or absence of Si with or without Cd. Cadmium, Si, and iron (Fe) accumulation in roots and shoots was analysed. Leaf protoplasts from plants grown without Cd were investigated for Cd uptake in the presence or absence of Si using the fluorescent dye, Leadmium Green AM. Roots and shoots of plants subjected to all four treatments were investigated regarding the expression of genes involved in the Cd uptake across the plasma membrane (i.e. LCT1) and efflux of Cd into apoplasm or vacuole from the cytosol (i.e. HMA2). In addition, phytochelatin (PC) content and PC gene (PCS1) expression were analysed. Expression of iron and metal transporter genes (IRT1 and NRAMP1) were also analysed. Results indicated that Si reduced Cd accumulation in plants, especially in shoot. Si reduced Cd transport into the cytoplasm when Si was added both directly during the uptake measurements and to the growth medium. Silicate downregulated LCT1 and HMA2 and upregulated PCS1. In addition, Si enhanced PC formation when Cd was present. The IRT1 gene, which was downregulated by Cd was upregulated by Si in root and shoot facilitating Fe transport in wheat. NRAMP1 was similarly expressed, though the effect was limited to roots. This work is the first to show how Si influences Cd uptake on the cellular level.

  • 4.
    Gul, Mehreen
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Bahauddin Zakariya University, Pakistan; University of Agriculture, Pakistan.
    Wakeel, A.
    Steffens, D.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Potassium-induced decrease in cytosolic Na+ alleviates deleterious effects of salt stress on wheat (Triticum aestivum L.)2019In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 21, no 5, p. 825-831Article in journal (Refereed)
    Abstract [en]

    Accumulation of NaCl in soil causes osmotic stress in plants, and sodium (Na+) and chloride (Cl-) cause ion toxicity, but also reduce the potassium (K+) uptake by plant roots and stimulate the K+ efflux through the cell membrane. Thus, decreased K+/Na+ ratio in plant tissue lead us to hypothesise that elevated levels of K+ in nutrient medium enhance this ratio in plant tissue and cytosol to improve enzyme activation, osmoregulation and charge balance. In this study, wheat was cultivated at different concentrations of K+ (2.2, 4.4 or 8.8 mm) with or without salinity (1, 60 or 120 mm NaCl) and the effects on growth, root and shoot Na+ and K+ distribution and grain yield were determined. Also, the cytosolic Na+ concentration was investigated, as well as photosynthesis rate and water potential. Salinity reduced fresh weight of both shoots and roots and dry weight of roots. The grain yield was significantly reduced under Na+ stress and improved with elevated K+ fertilisation. Elevated K+ level during cultivation prevented the accumulation of Na+ into the cytosol of both shoot and root protoplasts. Wheat growth at vegetative stage was transiently reduced at the highest K+ concentration, perhaps due to plants' efforts to overcome a high solute concentration in the plant tissue, nevertheless grain yield was increased at both K+ levels. In conclusion, a moderately elevated K+ application to wheat seedlings reduces tissue as well as cytosolic Na+ concentration and enhances wheat growth and grain yield by mitigating the deleterious effects of Na+ toxicity.

  • 5. Javed, M. Tariq
    et al.
    Akram, M. Sohail
    Tanwir, Kashif
    Chaudhary, Hassan Javed
    Ali, Qasim
    Stoltz, Eva
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Cadmium spiked soil modulates root organic acids exudation and ionic contents of two differentially Cd tolerant maize (Zea mays L.) cultivars2017In: Ecotoxicology and Environmental Safety, ISSN 0147-6513, E-ISSN 1090-2414, Vol. 141, p. 216-225Article in journal (Refereed)
    Abstract [en]

    Our earlier work described that the roots of two maize cultivars, grown hydroponically, differentially responded to cadmium (Cd) stress by initiating changes in medium pH depending on their Cd tolerance. The current study investigated the root exudation, elemental contents and antioxidant behavior of the same maize cultivars (cv. 3062 (Cd-tolerant) and cv. 31P41 (Cd-sensitive)] under Cd stress. Plants were maintained in a rhizobox-like system carrying soil spiked with Cd concentrations of 0, 10, 20, 30, 40 and 50 mu mol/kg soil. The root and shoot Cd contents increased, while Mg, Ca and Fe contents mainly decreased at higher Cd levels, and preferentially in the sensitive cultivar. Interestingly, the K contents increased in roots of cv. 3062 at low Cd treatments. The Cd stress caused acidosis of the maize root exudates predominantly in cv. 3062. The concentration of various organic acids was significantly increased in the root exudates of cv. 3062 with applied Cd levels. This effect was diminished in cv. 31P41 at higher Cd levels. Cd exposure increased the relative membrane permeability, anthocyanin (only in cv. 3062), proline contents and the activities of peroxidases (POD) and superoxide dismutase (SOD). The only exception was the catalase activity, which was diminished in both cultivars. Root Cd contents were positively correlated with the secretion of acetic acid, oxalic acid, glutamic acid, citric acid, and succinic acid. The antioxidants like POD and SOD exhibited a positive correlation with the organic acids under Cd stress. It is likly that a high exudation of dicarboxylic organic acids improves nutrient uptake and activities of antioxidants, which enables the tolerant cultivar to acclimatize in Cd polluted environment.

  • 6.
    Javed, M. Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Cadmium uptake in Elodea canadensis leaves and its interference with extra- and intra-cellular pH2014In: Plant Biology, ISSN 1435-8603, E-ISSN 1438-8677, Vol. 16, no 3, p. 615-621Article in journal (Refereed)
    Abstract [en]

    This study investigated cadmium (Cd) uptake in Elodea canadensis shoots under different photosynthetic conditions, and its effects on internal (cytosolic) and external pH. The plants were grown under photosynthetic (light) or non-photosynthetic (dark or in the presence of a photosynthetic inhibitor) conditions in the presence or absence of CdCl2 (0.5 mu m) in a medium with a starting pH of 5.0. The pH-sensitive dye BCECF-AM was used to monitor cytosolic pH changes in the leaves. Cadmium uptake in protoplasts and leaves was detected with a Cd-specific fluorescent dye, Leadmium Green AM, and with atomic absorption spectrophotometry. During cultivation for 3days without Cd, shoots of E.canadensis increased the pH of the surrounding water, irrespective of the photosynthetic conditions. This medium alkalisation was higher in the presence of CdCl2. Moreover, the presence of Cd also increased the cation exchange capacity of the shoots. The total Cd uptake by E.canadensis shoots was independent of photosynthetic conditions. Protoplasts from plants exposed to 0.5 mu m CdCl2 for 3days did not exhibit significant change in cytosolic [Cd2+] or pH. However, exposure to CdCl2 for 7days resulted in increased cytosolic [Cd2+] as well as pH. The results suggest that E.canadensis subjected to a low CdCl2 concentration initially sequesters Cd into the apoplasm, but under prolonged exposure, Cd is transported into the cytosol and subsequently alters cytosolic pH. In contrast, addition of 10-50 mu m CdCl2 directly to protoplasts resulted in immediate uptake of Cd into the cytosol.

  • 7.
    Javed, M. Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Cellular proton dynamics in Elodea canadensis leaves induced by cadmium2014In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 77, p. 15-22Article in journal (Refereed)
    Abstract [en]

    Our earlier investigations showed that Elodea canadensis shoots, grown in the presence of cadmium (Cd), caused basification of the surrounding medium. The present study was aimed to examine the proton dynamics of the apoplastic, cytosolic and vacuolar regions of E. canadensis leaves upon Cd exposure and to establish possible linkage between cellular pH changes and the medium basification. The changes in cytosolic calcium [Ca2+](cyt) was also investigated as the [Ca2+](cyt) and [pH](cyt) homeostasis are closely linked. The cellular H+ and Ca2+ concentrations were monitored by fluorescence microscopy and ion-specific fluorescent dyes. Cadmium concentration of leaf-cell walls was measured after plant cultivation at different fixed levels of starting pH. The protoplasts from E. canadensis leaves were isolated by use of a newly developed enzymatic method. Upon Cd addition, both cytosolic and vacuolar pH of leaf protoplasts increased with a concomitant rise in the cytosolic Ca2+ concentration. Time course studies revealed that changes in [Ca2+](cyt) and [PH](cyt) followed similar dynamics. Cadmium (0.5 mu M) exposure decreased the apoplastic pH by 0.85 units. The maximum cell wall bound Cd-contents were obtained in plants grown at low starting pH. It is concluded that Cd treatment causes apoplastic acidosis in E. canadensis leaves associated with enhanced Cd binding to the cell walls and, consequently, reduced Cd influx into the cytosol.

  • 8.
    Javed, M. Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Stoltz, Eva
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, Maria
    Changes in pH and organic acids in mucilage of Eriophorum angustifolium roots after exposure to elevated concentrations of toxic elements2012In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 20, no 3, p. 1876-1880Article in journal (Refereed)
    Abstract [en]

    The presence of Eriophorum angustifolium in mine tailings of pyrite maintains a neutral pH, despite weathering, thus lowering the release of toxic elements into acid mine drainage water. We investigated if the presence of slightly elevated levels of free toxic elements triggers the plant rhizosphere to change the pH towards neutral by increasing organic acid content. Plants were treated with a combination of As, Pb, Cu, Cd and Zn at different concentrations in nutrient medium and in soil in a rhizobox-like system for 48-120 hrs. The pH and organic acids were detected in the mucilage dissolved from root surface, reflecting the rhizosphere solution. Also the pH of root-cell apoplasm was investigated. Both apoplasmic and mucilage pH increased and the concentrations of organic acids enhanced in the mucilage with slightly elevated levels of toxic elements. When organic acid concentration was high, also the pH was high. Thus, efflux of organic acids from the roots of E. angustifolium may induce rhizosphere basification.

  • 9.
    Javed, Muhammad Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany.
    Cytosolic uptake of cadmium causes an extra- and intra-cellular basification in Elodea canadensisManuscript (preprint) (Other academic)
    Abstract [en]

    The current study was aimed to investigate the pH changes by Elodea canadensis shoots under different photosynthetic conditions in the presence and absence of cadmium (Cd) and its influence on Cd uptake. Plants were grown under light, dark and in the presence of the photosynthetic inhibitor (3-(3,4-dichlorophenyl)-1,1-dimethylurea) with and without 0.5 µM Cd in the solution at a starting pH of 5.0. The Cd uptake into the cytosol of leaf protoplasts was investigated by using a Cd-specific fluorescent dye, LeadmiumTM Green AM. Cadmium and proton dynamics were monitored in leaf protoplasts after plant exposure to 0.5 µM CdCl2 for 3 and 7 d, respectively. The pH sensitive dye BCECF-AM was used to detect cytosolic pH changes. The shoots increased the surrounding water pH, which enhanced Cd uptake. Beside pH increase by photosynthetic activity, E. canadensis possessed additional mechanisms to raise the surrounding water pH in the presence of Cd. The cytosolic cadmium (Cd2+cyt) fluorescence of leaf protoplasts increased upon addition of CdCl2 to the external medium, reflecting (Cd2+cyt) uptake. Plant exposure to 0.5 µM CdCl2 for 3 d did not induce significant changes in (Cd2+cyt)and [pH]cyt. However, the (Cd2+cyt) and pHcyt were significantly increased after plant exposure to 0.5 µM CdCl2 for 7d. This suggests that E. canadensis initially sequester Cd in its apoplasmic region depending upon the presence of acidic polysaccharides in its cell wall and external medium basification. With time Cd translocates into the cytosol and subsequently causes its basification.

  • 10.
    Javed, Muhammad Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Maria, Greger
    Stockholm University, Faculty of Science, Department of Botany.
    Cadmium induces cellular pH changes in Elodea canadensis and causes external basificationArticle in journal (Refereed)
    Abstract [en]

    Earlier investigations showed that Elodea canadensis causes a basification of the surrounding medium in the presence of cadmium. This study was aimed to investigate the mechanism by which Cd causes this plant to increase the surrounding water pH. Cd-induced pH changes in cytosol, vacuole and apoplastic regions of E. canadensis were monitored by fluorescence microscopy and pH-specific fluorescent dyes. Since cytosolic Ca2+ and pH homeostasis are closely linked, the cytosolic calcium [Ca2+]cytwas also investigated after Cd treatment. Cd binding to the cell walls of E. canadensis was investigated after cultivation of plants at different fixed pH. We developed a new enzymatic method for the isolation of protoplasts from E. canadensis leaves. Cd exposure resulted in a subsequent increase in both cytosolic and vacuolar pH of leaf protoplasts and concomitant rise in the [Ca2+]cyt. Changes in [Ca2+]cyt and [pH]cyt followed the same dynamics upon Cd addition, but the changes in [pH]cyt seemed to be prior to the [Ca2+]cyt changes. Cd treatment decreased the apoplastic pH by 0.85 units and Cd contents of cell walls were enhanced at low pH. In conclusion, Cd exposure decreased the apoplastic pH of E. canadensis and resulted in Cd binding to the cell walls which may prevent Cd influx to the cytosol. The results suggest that the Cd-induced apoplastic acidification can be one of the mechanisms to increase the surrounding medium pH by E. canadensis shoots.

  • 11.
    Javed, Muhammad Tariq
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Stoltz, Eva
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Botany.
    pH changes and organic acids exudation by Eriophorum angustifolium roots exposed to elevated concentration of toxic elementsArticle in journal (Refereed)
    Abstract [en]

    This study was aimed to investigate the influence of Eriophorum angustifolium roots on surrounding water pH in the presence of heavy metals and As, and the possible mechanism behind. We monitored the pH in the surrounding nutrient solution by E. angustifolium roots at a starting pH 3.5 and in the presence of a combination of As, Pb, Cu, Cd and Zn at different concentrations. The metal and As contents in the plant shoots and roots were analyzed as well as organic acids in the root exudates. Fluorescence microscopy and a pH-specific fluorescent dye were used to investigate the influence of different elements on apoplastic pH of E. angustifolium roots. The results showed that the roots have the ability to increase the rhizosphere pH even in the presence of different free metal ions and As. The plant root metal and As contents were significantly higher as compared with shoots. Metal and As treatment at higher concentrations significantly caused the apoplastic pH to increase in this species. Of the acids analyzed, the exudation of the oxalic, formic and succinic acids was significantly enhanced after metal and As exposure, as compared with control, giving the maximum concentration of these acids after 25 µM As, Cu, Zn, Pb and 2.5 µM Cd treatment. The roots of E. angustifolium respond to toxic ions by releasing organic acids, which transiently induce rhizosphere basification.

  • 12.
    Kader, Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Cytosolic calcium and pH signaling in plants under salinity stress2010In: Plant signaling and behavior, Vol. 5, no 3, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Calcium is one of the essential nutrients for growth and development of plants. It is an

    important component of various structures in cell wall and membranes. Besides some

    fundamental roles under normal condition, calcium functions as a major secondarymessenger

    molecule in plants under different developmental cues and various stress

    conditions including salinity stress. Also changes in cytosolic pH, pHcyt, either individually,

    or in coordination with changes in cytosolic Ca2+ concentration, [Ca2+]cyt, evoke a wide range

    of cellular functions in plants including signal transduction in plant-defense responses against

    stresses. It is believed that salinity stress, like other stresses, is perceived at cell membrane,

    either extra cellular or intracellular, which then triggers an intracellular-signaling cascade

    including the generation of secondary messenger molecules like Ca2+ and protons. The

    variety and complexity of Ca2+ and pH signaling result from the nature of the stresses as well

    as the tolerance level of the plant species against that specific stress. The nature of changes in

    [Ca2+]cyt concentration, in terms of amplitude, frequency and duration, is likely very

    important for decoding the specific downstream responses for salinity stress tolerance in

    planta. It has been observed that the signatures of [Ca2+]cyt and pH differ in various studies

  • 13.
    Kader, Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Sedel, Thorsten
    University of Bielefeld, Germany.
    Golldack, Dortje
    University of Bielefeld, Germany.
    Yemelyanov, Vladislav
    State University of St. Petersburg, Russia.
    Sodium sensing induces different changes in free cytosolic calcium concentration and pH in salt-tolerant and -sensitive rice (Oryza sativa) cultivars2007In: Physiologia Plantarum, ISSN 0031-9317, Vol. 130, p. 99-111Article in journal (Refereed)
    Abstract [en]

    Perception of salt stress in plant cells induces a change in the free cytosolic Ca2+, [Ca2+]cyt, which transfers downstream reactions toward salt tolerance. Changes in cytosolic H+ concentration, [H+]cyt, are closely linked to the [Ca2+]cyt dynamics under various stress signals. In this study, salt-induced changes in [Ca2+]cyt, and [H+]cyt and vacuolar [H+] concentrations were monitored in single protoplasts of rice (Oryza sativa L. indica cvs. Pokkali and BRRI Dhan29) by fluorescence microscopy. Changes in cytosolic [Ca2+] and [H+] were detected by use of the fluorescent dyes acetoxy methyl ester of calcium-binding benzofuran and acetoxy methyl ester of 2', 7'-bis-(2- carboxyethyl)-5-(and-6) carboxyfluorescein, respectively, and for vacuolar pH, fluorescent 6-carboxyfluorescein and confocal microscopy were used. Addition of NaCl induced a higher increase in [Ca21]cyt in the salt-tolerant cv. Pokkali than in the salt-sensitive cv. BRRI Dhan29. From inhibitor studies, we

    conclude that the internal stores appear to be the major source for [Ca2+]cyt increase in Pokkali, although the apoplast is more important in BRRI Dhan29. The [Ca21]cyt measurements in rice also suggest that Na1 should be sensed inside the cytosol, before any increase in [Ca2+]cyt occurs. Moreover, our results with individual mesophyll protoplasts suggest that ionic stress causes an increase in [Ca2+]cyt and that osmotic stress sharply decreases [Ca2+]cyt in rice. The [pH]cyt was differently shifted in the two rice cultivars in response to salt stress and may be coupled to different activities of the H1-ATPases. The changes in vacuolar pH were correlated with the expressional analysis of rice

    vacuolar H+-ATPase in these two rice cultivars.

  • 14.
    Kader, M Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Adaptation mechanisms in Rice (Oryza sativa) under salt stress2007In: 2nd World Conference on Stress: 3rd Cell Stress Society International Congress on Stress Responses in Biology and Mediin, 2007, p. 1-Conference paper (Refereed)
    Abstract [en]

    The project focuses on two important aspects of Na+ toxicity in salt-tolerant rice cv. Pokkali and salt-sensitive cv. BRRI Dhan29, namely i) how Na+ stress induces a change in cytosolic Ca2+, [Ca2+]cyt, and pH, [pH]cyt, and ii) how cells could maintain a low cytosolic Na+ and/or Na+/K+ ratio. The salt-induced changes in [Ca2+]cyt and [pH]cyt and their sources were monitored in single rice protoplasts by fluorescence microscopy. The expression of the transporter genes OsHKT1, OsHKT2 and OsVHA, which are thought to play a significant role in maintaining correct cytosolic Na+ and or Na+/K+ ratio, were examined in both rice cultivars under salt stress condition by real time RT-PCR and in situ PCR. The results show that Na+ must be sensed inside the cytosol, before any changes in [Ca2+]cyt and [pH]cyt occur. Sensing of Na+ induced different changes in [Ca2+]cyt and [pH]cyt in the two rice cultivars with different sources for the changes. The [pH]cyt changes were coupled to different

    H+-ATPases in the two cultivars. The expression analysis of OsHKT1, OsHKT2 and OsVHA showed variable and cell- specific induction in these cultivars under salt stress condition. The important mechanism for salt tolerance in cv. Pokkali was to keep cytosolic Na+ at a low level, by reducing Na+-influx (through down-regulation of OsHKT1) and compartmentalizing cytosolic Na+ into the vacuole (through the induction of vacuolar H+ATPase OsVHA, an energizer for the tonoplast Na+/H+ antiporter). Pokkali might also induce increased uptake of K+ through the induction of OsHKT2, as evident in this study. Vacuolar

    compartmentalization of Na+ is also present in salt-sensitive cv. BRRI Dhan29, but to a lesser extent and much later than in cv. Pokkali. The results suggest that the signaling and subsequent adaptive responses in the salt-tolerant rice cv. Pokkali are different from that in the salt-sensitive cv. BRRI Dhan29.

  • 15.
    Kader, Md Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Cellular traits for sodium tolerance in rice (Oryza sativa L.)2008Conference paper (Other academic)
    Abstract [en]

    Under salt stress the ability to reduce Na+-influx into the cytosol, and subsequently increase the compartmentalization of cytosolic Na+ into the vacuole, appeared to be the significant salt-tolerance determinant in salt-tolerant cv. Pokkali. These mechanisms were either absent or less efficient in the salt-sensitive cv. BRRI Dhan29.

  • 16.
    Kader, Md Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    Cellular traits for sodium tolerance in rice (Oryza sativa L.)2008In: Plant Biotechnology, ISSN 0289577, Vol. 25, no 3, p. 247-255Article in journal (Refereed)
    Abstract [en]

    Abstract

    The present review focuses on two important aspects of Na+ toxicity in rice (Oryza sativa L.), i) that Na+ stress induces different changes in cytosolic Ca2+, [Ca2+]cyt, and pH, [pH]cyt, in tolerant and sensitive cultivars, and ii) that cells from a tolerant cultivar can better maintain a low cytosolic Na+ and/or Na+/K+ ratio. Experiments with single rice protoplasts, fluorescence microscopy and specific ion-selective dyes suggest that Na+ must be sensed inside the cytosol, before any prolonged changes in [Ca2+]cyt and [pH]cyt occur. Inhibitor analyses show that Na+-induced increase in [pH]cyt in the tolerant cv. Pokkali, and a decrease in [pH]cyt in the sensitive cv. BRRI DHan29, likely are coupled to different H+-ATPases. Expression analysis of OsHKT2;1 (previous name OsHKT1), OsHKT2;2 (previous name OsHKT2) and OsVHA transcripts in rice using RT-PCR and fluorescence in situ-PCR, shows a variable and cell- specific induction in the two rice cultivars under salt stress condition. We conclude that the transient uptake of Na+, which occurs only in the tolerant cultivar, and the fast compartmentalization of Na+ into the vacuole, probably are the most important cellular traits for Na+-tolerance in rice. The low [Na+]cyt in cv. Pokkali might depend on the fast down-regulation of OsHKT2;1, causing less uptake of Na+, and fast up-regulation of the OsVHA transcript, and subsequent activation of the Na+/H+-anti-porter in the tonoplast. To decrease the cytosolic Na+/K+ ratio under Na+ toxicity, cv. Pokkali may also induce increased uptake of K+ through induction of OsHKT2;2, and other specific K+-transporter genes.

  • 17.
    Kader, Md Abdul
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Rasmusson, Allan
    University of Lund.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Expressions of HKT members in salt-tolerant and salt-sensitive rice cultivars are differentially regulated under salinity stress2009In: 9th IMPB Congress October 2009: Abiotic stress, Water, salts, minerals, 2009Conference paper (Other academic)
  • 18.
    Lindberg, Sylvia
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    kader, Md Abdul
    Bangladesh Agricultural University.
    Yemelyanov, Vladislav
    St Petersburg State University.
    Calcium signalling in plant cells under environmental stress2011In: Environmental adaptations and stress tolerance of plants in the era of climate change / [ed] Parvaiz A and Prasad MNV, New york, NY: Springer, 2011, 1, p. 325-360Chapter in book (Refereed)
    Abstract [en]

    A change of intracellular calcium concentration is an early event in a large array of biological processes in plants, such as cell division, polarity, growth and development at normal conditions and under adaptation to abiotic and biotic stresses. This chapter will focus on calcium signaling induced by different types of abiotic stress, such as salt, cold, anoxia, aluminium and heavy metal stresses. A minor part deals with biotic stress signaling. Most investigations, so far, concerned Ca2+ signaling in the cytosol, but the last years also signaling in the nucleus and other cell compartments such as mitochondria, ER and cell wall have been reported. We will compare the specific “signature” of calcium, including duration, amplitude and frequency of the signaling, which is induced by different stresses and is important for a change of the physiological function. Different stores for calcium take part in the signaling under various types of stresses. Of special interest is a comparison of signaling in tolerant and sensitive species and cultivars.

  • 19.
    Lindberg, Sylvia
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Premkumar, Albert
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Rasmussen, Ulla
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Schulz, Alexander
    Lager, Ida
    Phospholipases AtPLD1 and AtPLD2 function differently in hypoxia2018In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 162, no 1, p. 98-108Article in journal (Refereed)
    Abstract [en]

    Besides hydrolyzing different membrane phospholipids, plant phospholipases D and molecular species of their byproducts phosphatidic acids (PLDs/PAs) are involved in diverse cellular events such as membrane-cytoskeleton dynamics, hormone regulation and biotic and/or abiotic stress responses at cellular or subcellular levels. Among the 12 Arabidopsis PLD genes, PLD1 and PLD2 uniquely possess Ca2+-independent phox (PX) and pleckstrin (PH) homology domains. Here, we report that mutants deficient in these PLDs, pld1 and pld2, show differential sensitivities to hypoxia stimulus. In the present study, we used protoplasts of wild type and mutants and compared the hypoxia-induced changes in the levels of three major signaling mediators such as cytoplasmic free calcium [Ca-cyt.(2+)], hydrogen peroxide (H2O2) and PA. The concentrations of cytosolic Ca2+ and H2O2 were determined by fluorescence microscopy and the fluorescent dyes Fura 2-AM and CM-H(2)DCFDA, specific for calcium and H2O2, respectively, while PA production was analyzed by an enzymatic method. The study reveals that AtPLD1 is involved in reactive oxygen species (ROS) signaling, whereas AtPLD2 is involved in cytosolic Ca2+ signaling pathways during hypoxic stress. Hypoxia induces an elevation of PA level both in Wt and pld1, while the PA level is unchanged in pld2. Thus, it is likely that AtPLD2 is involved in PA production by a calcium signaling pathway, while AtPLD1 is more important in ROS signaling.

  • 20. Morgan, Sherif H.
    et al.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Maity, Pooja Jha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Geilfus, Christoph-Martin
    Plieth, Christoph
    Mühling, Karl-Hermann
    Calcium improves apoplastic-cytosolic ion homeostasis in salt-stressed Vicia faba leaves2017In: Functional Plant Biology, ISSN 1445-4408, E-ISSN 1445-4416, Vol. 44, no 5, p. 515-524Article in journal (Refereed)
    Abstract [en]

    Salinity disturbs both apoplastic and cytosolic Ca2+ and pH ([Ca2+](apo), [Ca2+](cyt), pH(apo) and pH(cyt)) homeostasis, and decreases plant growth. Seedlings of Vicia faba L. cv. Fuego were cultivated in hydroponics for 7 days under control, salinity (S), extra Ca (Ca) or salinity with extra Ca (S+Ca) conditions. The [Ca2+](apo), and pH(apo) in the leaves were then recorded in parallel by a pseudoratiometric method, described here for the first time. Lower [Ca2+](apo) and higher pH(apo) were obtained under salinity, whereas extra Ca supply increased the [Ca2+](apo) and acidified the pH(apo). Moreover, the ratiometric imaging recorded that [Ca2+](cyt) and pH(cyt) were highest in S+Ca plants and lowest in control plants. After all pretreatments, direct addition of NaC6H11O7 to leaves induced a decrease in [Ca2+](apo) in control and S+Ca plants, but not in S and Ca plants, and only slightly affected pH(apo). Addition of NaCl increased [Ca2+](cyt) in protoplasts from all plants but only transiently in protoplasts from S+Ca plants. Addition of NaCl decreased pH(cyt) in protoplasts from Ca-pretreated plants. We conclude that Ca supply improves both apoplastic and cytosolic ion homeostasis. In addition, NaC6H11O7 probably causes transport of Ca from the apoplast into the cytosol, thereby leading to a higher resting [Ca2+](cyt).

  • 21. Morgan, Sherif H.
    et al.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Muehling, Karl H.
    Calcium supply effects on wheat cultivars differing in salt resistance with special reference to leaf cytosol ion homeostasis2013In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 149, no 3, p. 321-328Article in journal (Refereed)
    Abstract [en]

    Salinity causes changes in cytosolic Ca2+, [Ca2+](cyt), Na+, [Na+](cyt) and pH, pH(cyt), which induce specific reactions and signals. Reactions causing a rebalancing of the physiological homeostasis of the cytosol could result in plant resistance and growth. Two wheat cultivars, Triticum aestivum, Seds1 and Vinjett, were grown in nutrient solution for 7days under moderate salinity (0 and 50mMNaCl) with and without extra addition of 5mMCaSO(4) to investigate the seedling-ion homeostasis under salinity. In the leaf protoplasts [Ca2+](cyt), [Na+](cyt) and pH(cyt) were detected using acetoxymethyl esters of the ion-specific dyes, Fura 2, SBFI and BCECF, respectively, and fluorescence microscopy. In addition, both cultivars were grown for 3weeks at 0, 50 and 125mMNaCl with, or without, extra addition of 5mMCaSO(4) to detect overall Na+ and Ca2+ concentrations in leaves and salinity effects on dry weights. In both cultivars, salinity decreased [Ca2+](cyt), while at extra Ca2+ supplied, [Ca2+](cyt) increased. The [Ca2+](cyt) increase was accompanied by increase in the overall Ca2+ concentrations in leaves and decrease in the overall Na+ concentration. Moreover, irrespective of Ca2+ treatment under salinity, the cultivars reacted in different ways; [Na+](cyt) significantly increased only in cv. Vinjett, while pH(cyt) increased only in cv. Seds1. Even at rather high total Na+ concentrations, the cytosolic concentrations were kept low in both cultivars. It is discussed whether the increase of [Ca2+](cyt) and pH(cyt) can contribute to salt tolerance and if the cytosolic changes are due to changes in overall Ca2+ and Na+ concentrations.

  • 22.
    Morgan, Sherif H.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Kiel, Germany; Cairo University, Egypt.
    Maity, Pooja Jha
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Geilfus, Christoph-Martin
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Muehling, Karl Hermann
    Leaf ion homeostasis and plasma membrane H+-ATPase activity in Vicia faba change after extra calcium and potassium supply under salinity2014In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 82, p. 244-253Article in journal (Refereed)
    Abstract [en]

    Salt stress in plants impacts apoplastic ion activities and cytosolic ionic homeostasis. The ameliorating effects exerted by calcium or potassium on compartmentation of ions in leaves under salinity are not fully understood. To clarify how calcium or potassium supply could ameliorate ion homeostasis and ATPase activities under salinity, 5 mM CaSO4 or 10 mM K2SO4 were added with, or without, 100 mM NaCl for 7 d and 21 d to Vicia faba grown in hydroponics. The apoplastic pH was detected with Oregon Green dextran dye in intact second-uppermost leaves by microscopy-based ratio imaging. The cytosolic Ca2+, Na+, K+ activities and pH were detected in protoplasts loaded with the acetoxy methyl-esters of Fura-2, SBFI, PBFI and BCECF, respectively, using epi-fluorescence microscopy. Furthermore, total Ca2+, Na+, K+ concentrations and growth parameters were investigated. The ATPase hydrolyzing activity increased with time, but decreased after long salinity treatment. The activity largely increased in calcium-treated plants, but was depressed in potassium-treated plants after 7 d. The calcium supply increased Vmax, and the ATPase activity increased with salinity in a non-competitive way for 7 d and 21 d. The potassium supply instead decreased activity competitively with Na+, after 21 d of salinity, with different effects on Km and Vmax. The confirmed higher ATPase activity was related with apoplast acidification, cytosol alkalinization and low cytosolic [Na+], and thus, might be an explanation why extra calcium improved shoot and leaf growth.

  • 23.
    Premkumar, Albert
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lager, Ida
    Rasmussen, Ulla
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Schulz, Alexander
    Arabidopsis PLDs with C2-domain function distinctively in hypoxia2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 167, no 1, p. 90-110Article in journal (Refereed)
    Abstract [en]

    Hypoxia (oxygen deprivation) causes metabolic disturbances at physiological, biochemical and genetic levels and results in decreased plant growth and development. Phospholipase D (PLD)-mediated signaling was reported for abiotic and biotic stress signaling events in plants. To investigate the participatory role of PLDs also in hypoxia signaling, we used wild type of Arabidopsis thaliana and 10 pld isoform mutants containing C2-domain. Hypoxia-induced changes in three major signaling players, namely, cytosolic free calcium (Ca-cyt(2+)), reactive oxygen species (ROS) and phosphatidic acid (PA), were determined in mesophyll protoplasts. The Ca-cyt(2+) and ROS levels were monitored by fluorescence microscopy and confocal imaging, while PA levels were quantified by an enzymatic method. Our findings reveal that the elevations of cytosolic calcium and PA are reduced in all the 10 mutants dysfunctional in PLD isoforms. The hypoxia-related changes in both calcium and ROS show different kinetic patterns depending on the type of PLD studied. Pharmacological experiments confirm that both external and internal sources contribute to calcium and ROS accumulation under hypoxia. PLD alpha 1-3, PLD beta 1 and PLD gamma 1-3 are likely involved in calcium signaling under hypoxia as well as in PA production, while all investigated PLDs, except for PLD gamma 3, take part in ROS elevation.

  • 24. Shahid, M.
    et al.
    Javed, M. T.
    Masood, S.
    Akram, M. S.
    Azeem, M.
    Ali, Q.
    Gilani, R.
    Basit, F.
    Abid, A.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Serratia sp. CP-13 augments the growth of cadmium (Cd)-stressed Linum usitatissimum L. by limited Cd uptake, enhanced nutrient acquisition and antioxidative potential2019In: Journal of Applied Microbiology, ISSN 1364-5072, E-ISSN 1365-2672, Vol. 126, no 6, p. 1708-1721Article in journal (Refereed)
    Abstract [en]

    Aims: The current study was aimed to evaluate the beneficial effects and bioremediation potential of a Cd-tolerant bacterial strain, Serratia sp. CP-13, on the physiological and biochemical functions of Linum usitatissimum L., under Cd stress.

    Methods and Results: The bacterial strain was isolated from the wastewater collection point of Chakera, Faisalabad, Pakistan, as this place contains industrial wastewater of the Faisalabad region. The Serratia sp. CP-13, identified through 16S rRNA gene sequence analysis, exhibited a significant phyto-beneficial potential in terms of in vitro inorganic phosphate solubilization, indole-3-acetic acid production and 1-aminocyclopropane-1-carboxylic acid deaminase activity. Effects of Serratia sp. CP-13 inoculation on L. usitatissimum were evaluated by growing the plants in CdCl2 (0, 5 or 10 mg kg(-1) dry soil)-spiked soil. Without inoculation of Serratia sp. CP-13, Cd stress significantly reduced the plant biomass as well as the quantity of proteins and photosynthetic pigments due to enhanced H2O2, malondialdehyde (MDA) contents and impaired nutrient homeostasis. Subsequently, Serratia sp. CP-13 increased the plant fresh and dry biomass, plant antioxidation capacity, whereas it decreased the lipid peroxidation under Cd stress. In parallel, Serratia sp. inoculation assisted the Cd-stressed plants to maintain an optimum level of nutrients (K, Ca, P, Mg, Fe and Mn).

    Conclusions: The isolated bacterial strain (Serratia sp. CP-13) when applied to Cd-stressed L. usitatissimum inhibited the Cd uptake, reduced Cd-induced lipid peroxidation, maintained the optimum level of nutrients and thereby, enhanced L. usitatissimum growth. The analysis of bio-concentration and translocation factor revealed that L. usitatissimum with Serratia sp. CP-13 inoculation sequestered Cd in plant rhizospheric zone.

    Significance and Impact of the Study: Serratia sp. CP-13 inoculation is a potential candidate for the development of low Cd-accumulating linseed and could be used for phytostabilization of Cd-contaminated rhizosphere/soil colloids.

  • 25.
    Shishova, Maria
    et al.
    Department of Plant Physiology and Biochemistry, St. Petersburg State University, 199034 St. Petersburg, Russia.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    A new perspective on auxin perception2010In: Journal of plant physiology (Print), ISSN 0176-1617, E-ISSN 1618-1328, Vol. 167, no 6, p. 417-422Article in journal (Refereed)
    Abstract [en]

    An important question in modern plant biology concerns the mechanisms of auxin perception. Despite the recently discovered soluble receptor, the F-box protein TIR1, there is no doubt that another type of signal perception exists, and is linked to the plasma membrane. Two models for the receptor have been suggested: either the receptor includes a protein kinase, or it is coupled with a G-protein. We propose a third model, acting through Ca2+-channels in the plasma membrane. The model is based on the revealed rapid auxin-induced reactions, including changes in the membrane potential, shifts in cytosol concentration of Ca2+ and H+ and modulation of cell sensitivity to hormones by the external Ca2+ concentration. Detailed inhibitor analysis with both living cells and isolated plasma membranes show that auxin might directly stimulate Ca2+ transport through the plasma membrane. A hypothetical scheme of auxin perception at the plasma membrane is suggested together with further transduction events. In addition, comparative analyses of auxin and serotonin perceptions are provided.

  • 26.
    Shishova, Maria
    et al.
    St Petersburg State University.
    Yemelyanov, Vladislav
    St Petersburg State University.
    Rudashevskaya, Elena
    St Petersburg State Universiry.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany. växtfysiologi.
    A shift in sensitivity to auxin within development of maize seedlings2007In: Journal of Plant Physiology, Vol. 164, p. 1323-1330Article in journal (Refereed)
    Abstract [en]

    The auxin-induced changes in cytosolic concentrations of Ca2+ and H+ ions were investigated in protoplasts from maize coleoptile cells at 3rd, 4th and 5th day of development of etiolated seedlings. The shifts in [Ca2+]cyt and [H+]cyt were detected by use of fluorescence microscopy in single protoplasts loaded with the tetra[acetoxymethyl]esters of the fluorescent calcium binding Fura 2, or pH-sensitive carboxy-fluorescein, BCECF, respectively. Both the auxin-induced shifts in the ion concentrations were specific to the physiologically active synthetic auxin, naphthalene-1-acetic acid (1-NAA), and not to the non-active naphthalene-2-acetic acid (2-NAA). Regardless of the age of the seedlings, the rise in [Ca2+]cyt was prior to the acidification in all investigated cases. The maximal acidification coincided with the highest amplitude of [Ca2+]cyt change, but not directly depended on the concentration of 1-NAA. Within aging of the seedlings the amplitude of auxin-induced [Ca2+]cyt elevation decreased. The shift in auxin-induced acidification was almost equal at 3rd and 4th day, but largely dropped at 5th day of development. The acidification was related to changes in the plasma

    membrane H+-ATPase activity, detected as phosphate release. The decrement in amplitude of both the tested auxin-triggered reactions well coincided with the end of the physiological function of the coleoptile. Hence the primary auxin-induced increase in [Ca2+]cyt, which is supposed to be an important element of hormone signal perception

    and transduction, can be used as a test for elucidation of plant cell sensitivity to auxin.

  • 27.
    Sun, Yujie
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. University of Copenhagen, Denmark.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Shabala, L.
    Morgan, S.
    Shabala, S.
    Jacobsen, S. -E.
    A comparative analysis of cytosolic Na+ changes under salinity between halophyte quinoa (Chenopodium quinoa) and glycophyte pea (Piswn sativwn)2017In: Environmental and Experimental Botany, ISSN 0098-8472, E-ISSN 1873-7307, Vol. 141, p. 154-160Article in journal (Refereed)
    Abstract [en]

    Sodium (Na+) uptake into the halophyte quinoa (Chenopodium quinoa Willd.) plants was compared with the uptake into pea (Pisum sativum L.), and related to changes in cytosolic pH and potassium (K+) concentration in plant tissues. The total uptake of Na+ and K+ in roots and shoots was analyzed and compared with net ion fluxes at the root xylem parenchyma, determined by ion-specific microelectrodes in a non-invasive way. The cytosolic changes of Na+ concentration, [Na-cyt(+)], and pH, pH(cyt), were measured by fluorescent probes, specific to Na+ and H+, using a dual-wavelength fluorescence microscopy. These changes were monitored in protoplasts after cultivation with or without 100 mM NaCl, and after addition of NaC1 to the protoplasts. Roots and shoots of quinoa controls contained much higher K+ levels than pea roots and shoots, and the K+ levels increased even more after salinity treatments in quinoa. The cytosolic uptake of Na+ in quinoa protoplasts was transient if less than 200 mM NaCl was added, while in pea the Na+ concentration increased even upon addition of 50 mM Na+ and gradually increased with time. Saline conditions during cultivation increased pH(cyt) of both species. However, with a direct addition of NaCl to control protoplasts only a small increase was seen in pea pH(cyt) while in quinoa this increase was much larger. The different reactions of pH(cyt) to salinity when NaCl was added to salinity-treated seedlings may reflect an increased proton pump activity in quinoa, while this activation is lacking in pea. ABA addition to the root xylem parenchyma cells induced a net efflux of K+ and acidification of the xylem. On the other hand, 20 mM NaC1 addition induced a net flux of protons in both species, and a net K+ flux in pea, but not in quinoa, probably since such a low concentration is not a stress for quinoa. It is suggested that salinity tolerance in quinoa is achieved by a faster removal of Na+ from the cytosol and a high K+ concentration in roots and shoots under salinity, resulting in a high K+/Na+ ratio, and that this mechanism is driven by a higher proton pump activity, compared with glycophytic pea species.

  • 28. Tanwir, Kashif
    et al.
    Akram, M. Sohail
    Masood, Sajid
    Chaudhary, Hassan Javed
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Javed, M. Tariq
    Cadmium-induced rhizospheric pH dynamics modulated nutrient acquisition and physiological attributes of maize (Zea mays L.)2015In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 22, no 12, p. 9193-9203Article in journal (Refereed)
    Abstract [en]

    Cadmium (Cd) is a highly mobile toxic element in soil-plant systems that interferes with plant growth and nutrient acquisition by modulations in the rhizospheric environment. The current study investigated the influence of maize roots on the medium pH, alterations in nutrient uptake, and impact on the plant's physiological attributes under Cd stress. Among the nine maize cultivars, subjected to Cd stress (9.15 mg/kg of sand), one was identified as Cd tolerant (3062-Pioneer) and the second as Cd sensitive (31P41-Pioneer). The selected maize cultivars were grown in nutrient solutions supplemented with 0, 10, 20, 30, 40, or 50 mu M CdCl2 under controlled conditions and a starting pH of 6.0. The rhizospheric pH dynamics were monitored each day up to 3 days. Both cultivars caused medium basification; however, the response was different at low (10 and 20 mu M) Cd treatments (sensitive cultivar caused medium basification) and at higher (50 mu M) Cd treatment (tolerant cultivar caused medium basification). Furthermore, higher Cd was accumulated by the sensitive cultivar which was predominantly found in the roots. Higher Cd levels in the medium resulted in increased uptake and translocation of both Cd and K (in the tolerant cultivar) or only Cd (in the sensitive cultivar). Uptake of other nutrients (Ca, Zn, and Fe) was antagonistically affected by Cd stress in both cultivars. Moreover, Cd stress significantly impaired chlorophyll content, catalase activity, and total protein content; irrespective of the genotype. The malondialdehyde (MDA) content was found to increase, in both cultivars, together with Cd level. However, the extent to which Cd interfered with the studied attributes was more pronounced in the sensitive cultivar as compared to the tolerant one. It is concluded that the maize roots responded to Cd stress by initiating modulations of medium pH which might be dependent on Cd tolerance levels. The study results may help to develop strategies to reduce Cd accumulation in maize and decontamination of metal-polluted soil sediments.

  • 29. Yemelyanov, Vladislav
    et al.
    Shishova, Maria
    St Petersburg State University.
    Chirkova, TV
    St Petersburg State University.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Anoxia-induced elevation of cytosolic Ca2+ concentration depends on different Ca2+ sources in rice and wheat protoplasts2011In: Planta, Vol. 234, p. 271-280Article in journal (Refereed)
    Abstract [en]

    The anoxia-dependent elevation of cytosolicCa2+ concentration, [Ca2+]cyt, was investigated in plants differing in tolerance to hypoxia. The [Ca2+]cyt was measuredby fluorescence microscopy in single protoplastsloaded with the calcium-fluoroprobe Fura 2-AM. Imposition of anoxia led to a fast (within 3 min) significant elevationof [Ca2+]cyt in rice leaf protoplasts. A tenfold drop in the external Ca2+ concentration (to 0.1 mM) resulted inconsiderable decrease of the [Ca2+]cyt shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La3+ and EGTA) and intracellular membrane Ca2+-channel antagonists(Li+, ruthenium red and cyclosporine A) reduced the anoxic Ca2+-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca2+]cyt. In wheat leaf protoplasts, the amplitude of the Ca2+-shift little depended on the external level of Ca2+. Wheat root protoplasts were characterized by a small shift of [Ca2+]cyt under anoxia. Plasmalemma Ca2+-channel blockers had little effect on the elevation of cytosolic Ca2+ in wheat protoplasts. Intact rice seedlings absorbed Ca2+ from the external medium under anoxic treatment. On the contrary,wheat seedlings were characterized by leakage of Ca2+. Verapamil abolished the Ca2?+influx in rice roots and Ca2+ efflux from wheat roots. Anoxia-induced [Ca2+]cyt elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca2+ stores are important for anoxic [Ca2+]cyt elevation in rice, whereas the hypoxia-intolerant wheat does not requireexternal sources for [Ca2+]cyt rise. Leaf and root protoplasts similarly responded to anoxia, independent of theirorgan origin.

  • 30.
    Zanella, Letizia
    et al.
    University of Rome La Sapienza.
    Brunetti, Patrizia
    University of Rome La Sapienza.
    Cardarelli, Maura
    University of Rome La Sapienza.
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Botany.
    Sanita di Toppi, Luigi
    University of Rome La Sapienza.
    Altamura, Maria Maddalena
    University of Rome La Sapienza.
    Falasca, Guiseppina
    University of Rome La Sapienza.
    Overexpression of AtPCS1 gene affects Cd tolerance in Arabidopsis thaliana2009In: / [ed] ., 2009Conference paper (Other academic)
  • 31. Zanella, Letizia
    et al.
    Fattorini, Laura
    Brunetti, Patrizia
    Roccotiello, Enrica
    Cornara, Laura
    D'Angeli, Simone
    Della Rovere, Federica
    Cardarelli, Maura
    Barbieri, Maurizio
    di Toppi, Luigi Sanita
    Degola, Francesca
    Lindberg, Sylvia
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Altamura, Maria Maddalena
    Falasca, Giuseppina
    Overexpression of AtPCS1 in tobacco increases arsenic and arsenic plus cadmium accumulation and detoxification2016In: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 243, no 3, p. 605-622Article in journal (Refereed)
    Abstract [en]

    Main conclusion The heterologous expression of AtPCS1 in tobacco plants exposed to arsenic plus cadmium enhances phytochelatin levels, root As/Cd accumulation and pollutants detoxification, but does not prevent root cyto-histological damages. High phytochelatin (PC) levels may be involved in accumulation and detoxification of both cadmium (Cd) and arsenic (As) in numerous plants. Although polluted environments are frequently characterized by As and Cd coexistence, how increased PC levels affect the adaptation of the entire plant and the response of its cells/tissues to a combined contamination by As and Cd needs investigation. Consequently, we analyzed tobacco seedlings overexpressing Arabidopsis phytochelatin synthase1 gene (AtPCS1) exposed to As and/or Cd, to evaluate the levels of PCs and As/Cd, the cyto-histological modifications of the roots and the Cd/As leaf extrusion ability. When exposed to As and/or Cd the plants overexpressing AtPCS1 showed higher PC levels, As plus Cd root accumulation, and detoxification ability than the non-overexpressing plants, but a blocked Cd-extrusion from the leaf trichomes. In all genotypes, As, and Cd in particular, damaged lateral root apices, enhancing cell-vacuolization, causing thinning and stretching of endodermis initial cells. Alterations also occurred in the primary structure region of the lateral roots, i. e., cell wall lignification in the external cortex, cell hypertrophy in the inner cortex, crushing of endodermis and stele, and nuclear hypertrophy. Altogether, As and/or Cd caused damage to the lateral roots (and not to the primary one), with such damage not counteracted by AtPCS1 overexpression. The latter, however, positively affected accumulation and detoxification to both pollutants, highlighting that Cd/As accumulation and detoxification due to PCS1 activity do not reduce the cyto-histological damage.

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