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Berlin Brandenburg

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  • 1
    Language: English
    In: Marine Biotechnology, 2013, Vol.15(4), pp.437-444
    Description: Marine microheterotrophs thraustochytrids are emerging as a potential source for commercial production of polyunsaturated fatty acids (PUFA) that have nutritional and pharmacological values. With prospective demand for PUFAs increasing, biotechnological companies are looking for potential increases in those valuable products. However, high levels of NaCl in the culture media required for optimal thraustochytrid growth and PUFA production poses a significant problem to the biotechnological industry due to corrosion of fermenters calling for a need to reduce the amount of NaCl in the culture media, without imposing penalties on growth and yield of cultured organisms. Earlier, as reported by Shabala et al. (Environ Microbiol 11:1835–1843, 2009), we have shown that thraustochytrids use sodium predominantly for osmotic adjustment purposes and, as such, can be grown in low-salt environment without growth penalties, providing the media osmolality is adjusted. In this study, we verify if that conclusion, made for one specific strain and osmolyte only, is applicable to the larger number of strains and organic osmotica, as well as address the issue of yield quality (e.g., PUFA production in low-saline media). Using mannitol and sucrose for osmotic adjustment of the growth media enabled us to reduce NaCl concentration down to 1 mM; this is 15–100-fold lower than any method proposed so far. At the same time, the yield of essential PUFAs was increased by 15 to 20 %. Taken together, these results suggest that the proposed method can be used in industrial fermenters for commercial PUFA production.
    Keywords: Thraustochytrids ; Biotechnology ; Fermenter corrosion ; Osmotic adjustment ; Compatible solutes ; Polyunsaturated fatty acids (PUFA)
    ISSN: 1436-2228
    E-ISSN: 1436-2236
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 09 June 2015, Vol.112(23), pp.7309-14
    Description: The Darwin plant Dionaea muscipula is able to grow on mineral-poor soil, because it gains essential nutrients from captured animal prey. Given that no nutrients remain in the trap when it opens after the consumption of an animal meal, we here asked the question of how Dionaea sequesters prey-derived potassium. We show that prey capture triggers expression of a K(+) uptake system in the Venus flytrap. In search of K(+) transporters endowed with adequate properties for this role, we screened a Dionaea expressed sequence tag (EST) database and identified DmKT1 and DmHAK5 as candidates. On insect and touch hormone stimulation, the number of transcripts of these transporters increased in flytraps. After cRNA injection of K(+)-transporter genes into Xenopus oocytes, however, both putative K(+) transporters remained silent. Assuming that calcium sensor kinases are regulating Arabidopsis K(+) transporter 1 (AKT1), we coexpressed the putative K(+) transporters with a large set of kinases and identified the CBL9-CIPK23 pair as the major activating complex for both transporters in Dionaea K(+) uptake. DmKT1 was found to be a K(+)-selective channel of voltage-dependent high capacity and low affinity, whereas DmHAK5 was identified as the first, to our knowledge, proton-driven, high-affinity potassium transporter with weak selectivity. When the Venus flytrap is processing its prey, the gland cell membrane potential is maintained around -120 mV, and the apoplast is acidified to pH 3. These conditions in the green stomach formed by the closed flytrap allow DmKT1 and DmHAK5 to acquire prey-derived K(+), reducing its concentration from millimolar levels down to trace levels.
    Keywords: Akt ; Cipk ; Dionaea Muscipula ; Hak5 ; Transporter ; Calcium -- Metabolism ; Droseraceae -- Metabolism ; Potassium -- Metabolism ; Protein Kinases -- Metabolism
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 3
    In: Journal Of Experimental Botany, 2016, Vol. 67(15), pp.4611-4625
    Description: This work provides the mechanistic explanation for differential salt stress sensitivity amongst Brassica species and links it with regulation of root plasma membrane potential and the cytosolic K/Na ratio Brassica species are known to possess significant inter and intraspecies variability in salinity stress tolerance, but the cell-specific mechanisms conferring this difference remain elusive. In this work, the role and relative contribution of several key plasma membrane transporters to salinity stress tolerance were evaluated in three Brassica species ( B. napus , B. juncea , and B. oleracea ) using a range of electrophysiological assays. Initial root growth assay and viability staining revealed that B. napus was most tolerant amongst the three species, followed by B. juncea and B. oleracea . At the mechanistic level, this difference was conferred by at least three complementary physiological mechanisms: (i) higher Na + extrusion ability from roots resulting from increased expression and activity of plasma membrane SOS1-like Na + /H + exchangers; (ii) better root K + retention ability resulting from stress-inducible activation of H + -ATPase and ability to maintain more negative membrane potential under saline conditions; and (iii) reduced sensitivity of B. napus root K + -permeable channels to reactive oxygen species (ROS). The last two mechanisms played the dominant role and conferred most of the differential salt sensitivity between species. Brassica napus plants were also more efficient in preventing the stress-induced increase in GORK transcript levels and up-regulation of expression of AKT1 , HAK5 , and HKT1 transporter genes. Taken together, our data provide the mechanistic explanation for differential salt stress sensitivity amongst these species and shed light on transcriptional and post-translational regulation of key ion transport systems involved in the maintenance of the root plasma membrane potential and cytosolic K/Na ratio as a key attribute for salt tolerance in Brassica species.
    Keywords: H - Atpase ; Ion Homeostasis ; Membrane Potential ; Potassium Retention ; Ros Detoxification ; Sodium Exclusion ; Tissue Tolerance.
    ISSN: 0022-0957
    E-ISSN: 1460-2431
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  • 4
    In: Physiologia Plantarum, September 2012, Vol.146(1), pp.26-38
    Description: Two components of salinity stress are a reduction in water availability to plants and the formation of reactive oxygen species. In this work, we have used quinoa (), a dicotyledonous C3 halophyte species displaying optimal growth at approximately 150 m NaCl, to study mechanisms by which halophytes cope with the afore‐mentioned components of salt stress. The relative contribution of organic and inorganic osmolytes in leaves of different physiological ages (e.g. positions on the stem) was quantified and linked with the osmoprotective function of organic osmolytes. We show that the extent of the oxidative stress (UV‐B irradiation) damage to photosynthetic machinery in young leaves is much less when compared with old leaves, and attribute this difference to the difference in the size of the organic osmolyte pool (1.5‐fold difference under control conditions; sixfold difference in plants grown at 400 m NaCl). Consistent with this, salt‐grown plants showed higher Fv/Fm values compared with control plants after UV‐B exposure. Exogenous application of physiologically relevant concentrations of glycine betaine substantially mitigated oxidative stress damage to PSII, in a dose‐dependent manner. We also show that salt‐grown plants showed a significant (approximately 30%) reduction in stomatal density observed in all leaves. It is concluded that accumulation of organic osmolytes plays a dual role providing, in addition to osmotic adjustment, protection of photosynthetic machinery against oxidative stress in developing leaves. It is also suggested that salinity‐induced reduction in stomatal density represents a fundamental mechanism by which plants optimize water use efficiency under saline conditions.
    Keywords: Universities And Colleges -- Physiological Aspects ; Photosynthesis -- Physiological Aspects ; Oxidative Stress -- Physiological Aspects ; Salinity -- Physiological Aspects ; Quinoa -- Physiological Aspects ; Machinery -- Physiological Aspects ; Glycine -- Physiological Aspects ; Water Use -- Physiological Aspects;
    ISSN: 0031-9317
    E-ISSN: 1399-3054
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  • 5
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 02 May 2017, Vol.114(18), pp.4822-4827
    Description: The Venus flytrap captures insects and consumes their flesh. Prey contacting touch-sensitive hairs trigger traveling electrical waves. These action potentials (APs) cause rapid closure of the trap and activate secretory functions of glands, which cover its inner surface. Such prey-induced haptoelectric stimulation activates the touch hormone jasmonate (JA) signaling pathway, which initiates secretion of an acidic hydrolase mixture to decompose the victim and acquire the animal nutrients. Although postulated since Darwin's pioneering studies, these secretory events have not been recorded so far. Using advanced analytical and imaging techniques, such as vibrating ion-selective electrodes, carbon fiber amperometry, and magnetic resonance imaging, we monitored stimulus-coupled glandular secretion into the flytrap. Trigger-hair bending or direct application of JA caused a quantal release of oxidizable material from gland cells monitored as distinct amperometric spikes. Spikes reminiscent of exocytotic events in secretory animal cells progressively increased in frequency, reaching steady state 1 d after stimulation. Our data indicate that trigger-hair mechanical stimulation evokes APs. Gland cells translate APs into touch-inducible JA signaling that promotes the formation of secretory vesicles. Early vesicles loaded with H and Cl fuse with the plasma membrane, hyperacidifying the "green stomach"-like digestive organ, whereas subsequent ones carry hydrolases and nutrient transporters, together with a glutathione redox moiety, which is likely to act as the major detected compound in amperometry. Hence, when glands perceive the haptoelectrical stimulation, secretory vesicles are tailored to be released in a sequence that optimizes digestion of the captured animal.
    Keywords: Dionaea Muscipula ; Amperometry ; Exocytosis ; Plant Digestion ; Secretion ; Insecta ; Droseraceae -- Physiology ; Exocytosis -- Physiology ; Signal Transduction -- Physiology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 6
    Language: English
    In: Plant physiology, September 2013, Vol.163(1), pp.253-62
    Description: Salinity (NaCl) stress impairs plant growth and inflicts severe crop losses. In roots, increasing extracellular NaCl causes Ca²⁺ influx to elevate cytosolic free Ca²⁺ ([Ca²⁺](cyt)) as a second messenger for adaptive signaling. Amplification of the signal involves plasma membrane reduced nicotinamide adenine dinucleotide phosphate oxidase activation, with the resultant reactive oxygen species triggering Ca²⁺ influx. The genetic identities of the Ca²⁺-permeable channels involved in generating the [Ca²⁺](cyt) signal are unknown. Potential candidates in the model plant Arabidopsis (Arabidopsis thaliana) include annexin1 (AtANN1). Here, luminescent detection of [Ca²⁺](cyt) showed that AtANN1 responds to high extracellular NaCl by mediating reactive oxygen species-activated Ca²⁺ influx across the plasma membrane of root epidermal protoplasts. Electrophysiological analysis revealed that root epidermal plasma membrane Ca²⁺ influx currents activated by NaCl are absent from the Atann1 loss-of-function mutant. Both adaptive signaling and salt-responsive production of secondary roots are impaired in the loss-of-function mutant, thus identifying AtANN1 as a key component of root cell adaptation to salinity.
    Keywords: Annexins -- Physiology ; Arabidopsis -- Metabolism ; Arabidopsis Proteins -- Physiology ; Calcium Signaling -- Genetics
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 7
    Language: English
    In: FEBS Letters, 18 March 2014, Vol.588(6), pp.1008-1015
    Description: Cyclic mononucleotides are messengers in plant stress responses. Here we show that hydrogen peroxide (H O ) induces rapid net K -efflux and Ca -influx in Arabidopsis roots. Pre-treatment with either 10 μM cAMP or cGMP for 1 or 24 h does significantly reduce net K -leakage and Ca -influx, and in the case of the K -fluxes, the cell permeant cyclic mononucleotides are more effective. We also examined the effect of 10 μM of the cell permeant 8-Br-cGMP on the Arabidopsis microsomal proteome and noted a specific increase in proteins with a role in stress responses and ion transport, suggesting that cGMP is sufficient to directly and/or indirectly induce complex adaptive changes to cellular stresses induced by H O .
    Keywords: Plant Stress ; Hydrogen Peroxide ; Cyclic Mononucleotide ; Camp ; Cgmp ; Ion Flux ; Proteomic ; Arabidopsis Thaliana ; Biology ; Chemistry ; Anatomy & Physiology
    ISSN: 0014-5793
    E-ISSN: 1873-3468
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  • 8
    Language: English
    In: Biomolecular concepts, 01 October 2011, Vol.2(5), pp.407-19
    Description: Plants and bacteria respond to hyperosmotic stress by an increase in intracellular osmolality, adjusting their cell turgor to altered growth conditions. This can be achieved either by increased uptake or de novo synthesis of a variety of organic osmolytes (so-called 'compatible solutes'), or by controlling fluxes of ions across cellular membranes. The relative contributions of each of these mechanisms have been debated in literature for many years and remain unresolved. This paper summarises all the arguments and reopens a discussion on the efficiency and strategies of osmotic adjustment in plants and bacteria. We show that the bulk of osmotic adjustment in both plants and bacteria is achieved by increased accumulation of inorganic osmolytes such as K+, Na+ and Cl-. This is applicable to both halophyte and glycophyte species. At the same time, de novo synthesis of compatible solutes is an energetically expensive and slow option and can be used only for the fine adjustment of the cell osmotic potential. The most likely role the organic osmolytes play in osmotic adjustment is in osmoprotection of key membrane transport proteins and reactive oxygen species (ROS) scavenging. The specific mechanisms by which compatible solutes regulate activity of ion transporters remain elusive and require more thorough investigation. It is concluded that creating transgenic species with increased levels of organic osmolytes by itself is counterproductive due to high yield penalties; all these attempts should be complemented by a concurrent increase in the accumulation of inorganic ions directly used for osmotic adjustment.
    Keywords: Osmosis ; Bacteria ; Compatible Solutes ; Inorganic Ion ; Osmolyte ; Osmosensing ; Potassium ; Ros Scavenging ; Sodium;
    ISSN: 1868-5021
    E-ISSN: 1868503X
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  • 9
    In: Journal Of Experimental Botany, 2016, Vol. 67(3), pp.835-844
    Description: Improved salinity stress tolerance in wheat Nax lines is achieved by transcriptional and post-translational down-regulation of Na + loading into the xylem by a SOS1 transporter. Salinity stress tolerance in durum wheat is strongly associated with a plant’s ability to control Na + delivery to the shoot. Two loci, termed Nax1 and Nax2 , were recently identified as being critical for this process and the sodium transporters HKT1;4 and HKT1;5 were identified as the respective candidate genes. These transporters retrieve Na + from the xylem, thus limiting the rates of Na + transport from the root to the shoot. In this work, we show that the Nax loci also affect activity and expression levels of the SOS1-like Na + /H + exchanger in both root cortical and stelar tissues. Net Na + efflux measured in isolated steles from salt-treated plants, using the non-invasive ion flux measuring MIFE technique, decreased in the sequence: Tamaroi (parental line)〉 Nax1 = Nax2 〉 Nax1:Nax2 lines. This efflux was sensitive to amiloride (a known inhibitor of the Na + /H + exchanger) and was mirrored by net H + flux changes. TdSOS1 relative transcript levels were 6–10-fold lower in Nax lines compared with Tamaroi. Thus, it appears that Nax loci confer two highly complementary mechanisms, both of which contribute towards reducing the xylem Na + content. One enhances the retrieval of Na + back into the root stele via HKT1;4 or HKT1;5, whilst the other reduces the rate of Na + loading into the xylem via SOS1. It is suggested that such duality plays an important adaptive role with greater versatility for responding to a changing environment and controlling Na + delivery to the shoot.
    Keywords: Hkt Transporter ; Potassium ; Salinity Stress ; Sequestration ; Sodium ; Xylem Loading.
    ISSN: 0022-0957
    E-ISSN: 1460-2431
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  • 10
    In: Journal of Experimental Botany, 2018, Vol. 69(3), pp.667-680
    Description: GORK channel-mediated K + retention in roots is central to adaptation and signalling under hypoxia; this trait may be used as a physiological marker in waterlogging tolerance-oriented breeding programmes. Oxygen depletion under waterlogged conditions results in a compromised operation of H + -ATPase, with strong implications for membrane potential maintenance, cytosolic pH homeostasis, and transport of all nutrients across membranes. The above effects, however, are highly tissue specific and time dependent, and the causal link between hypoxia-induced changes to the cell’s ionome and plant adaptive responses to hypoxia is not well established. This work aimed to fill this gap and investigate the effects of oxygen deprivation on K + signalling and homeostasis in plants, and potential roles of GORK (depolarization-activated outward-rectifying potassium) channels in adaptation to oxygen-deprived conditions in barley. A significant K + loss was observed in roots exposed to hypoxic conditions; this loss correlated with the cell’s viability. Stress-induced K + loss was stronger in the root apex immediately after stress onset, but became more pronounced in the root base as the stress progressed. The amount of K + in shoots of plants grown in waterlogged soil correlated strongly with K + flux under hypoxia measured in laboratory experiments. Hypoxia induced membrane depolarization; the severity of this depolarization was less pronounced in the tolerant group of cultivars. The expression of GORK was down-regulated by 1.5-fold in mature root but it was up-regulated by 10-fold in the apex after 48 h hypoxia stress. Taken together, our results suggest that the GORK channel plays a central role in K + retention and signalling under hypoxia stress, and measuring hypoxia-induced K + fluxes from the mature root zone may be used as a physiological marker to select waterlogging-tolerant varieties in breeding programmes.
    Keywords: Gork ; H - Atpase ; H - Ppase ; Hypoxia ; Ionic Homeostasis ; Potassium ; Signalling ; Viability Staining ; Waterlogging
    ISSN: 0022-0957
    E-ISSN: 1460-2431
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