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  • Hedrich, Rainer  (21)
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  • 1
    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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  • 2
    Language: English
    In: Plant physiology, November 2012, Vol.160(3), pp.1515-29
    Description: Understanding seasonality and longevity is a major challenge in tree biology. In woody species, growth phases and dormancy follow one another consecutively. In the oldest living individuals, the annual cycle may run for more than 1,000 years. So far, however, not much is known about the processes triggering reactivation from dormancy. In this study, we focused on wood rays, which are known to play an important role in tree development. The transition phase from dormancy to flowering in early spring was compared with the phase of active growth in summer. Rays from wood samples of poplar (Populus × canescens) were enriched by laser microdissection, and transcripts were monitored by poplar whole-genome microarrays. The resulting seasonally varying complex expression and metabolite patterns were subjected to pathway analyses. In February, the metabolic pathways related to flower induction were high, indicating that reactivation from dormancy was already taking place at this time of the year. In July, the pathways related to active growth, like lignin biosynthesis, nitrogen assimilation, and defense, were enriched. Based on "marker" genes identified in our pathway analyses, we were able to validate periodical changes in wood samples by quantitative polymerase chain reaction. These studies, and the resulting ray database, provide new insights into the steps underlying the seasonality of poplar trees.
    Keywords: Seasons ; Populus -- Cytology ; Trees -- Physiology ; Wood -- Cytology
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 3
    Language: English
    In: Oecologia, 2014, Vol.174(3), pp.839-851
    Description: Plant carnivory represents an exceptional means to acquire N. Snap traps of Dionaea muscipula serve two functions, and provide both N and photosynthate. Using 13 C/ 15 N-labelled insect powder, we performed feeding experiments with Dionaea plants that differed in physiological state and N status (spring vs. autumn plants). We measured the effects of 15 N uptake on light-saturated photosynthesis ( A max ), dark respiration ( R D ) and growth. Depending on N status, insect capture briefly altered the dynamics of R D / A max , reflecting high energy demand during insect digestion and nutrient uptake, followed by enhanced photosynthesis and growth. Organic N acquired from insect prey was immediately redistributed, in order to support swift renewal of traps and thereby enhance probability of prey capture. Respiratory costs associated with permanent maintenance of the photosynthetic machinery were thereby minimized. Dionaea’s strategy of N utilization is commensurate with the random capture of large prey, occasionally transferring a high load of organic nutrients to the plant. Our results suggest that physiological adaptations to unpredictable resource availability are essential for Dionaea’s success with regards to a carnivorous life style.
    Keywords: Plant carnivory ; Cost/benefit ; Photosynthetic efficiency ; Respiration ; Nitrogen uptake
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 4
    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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  • 5
    In: New Phytologist, April 2017, Vol.214(2), pp.597-606
    Description: The present study was performed to elucidate the fate of carbon (C) and nitrogen (N) derived from protein of prey caught by carnivorous Dionaea muscipula. For this, traps were fed 13C/15N‐glutamine (Gln). The release of 13CO2 was continuously monitored by isotope ratio infrared spectrometry. After 46 h, the allocation of C and N label into different organs was determined and tissues were subjected to metabolome, proteome and transcriptome analyses. Nitrogen of Gln fed was already separated from its C skeleton in the decomposing fluid secreted by the traps. Most of the Gln‐C and Gln‐N recovered inside plants were localized in fed traps. Among nonfed organs, traps were a stronger sink for Gln‐C compared to Gln‐N, and roots were a stronger sink for Gln‐N compared to Gln‐C. A significant amount of the Gln‐C was respired as indicated by 13C‐CO2 emission, enhanced levels of metabolites of respiratory Gln degradation and increased abundance of proteins of respiratory processes. Transcription analyses revealed constitutive expression of enzymes involved in Gln metabolism in traps. It appears that prey not only provides building blocks of cellular constituents of carnivorous Dionaea muscipula, but also is used for energy generation by respiratory amino acid degradation.
    Keywords: Amino Acid Catabolism ; Carbon Partitioning ; Dionaea Muscipula Venus Flytrap ; Glutamine ; Nitrogen N Partitioning ; Plant Carnivory ; Respiratory Degradation
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 6
    Language: English
    In: Environmental Pollution, November 2018, Vol.242, pp.905-913
    Description: Vegetation in the Arabian Peninsula is facing high and steadily rising tropospheric ozone pollution. However, little is known about the impacts of elevated ozone on date palms, one of the most important indigenous economic species. To elucidate the physiological responses of date palm to peak levels of acute ozone exposure, seedlings were fumigated with 200 ppb ozone for 8 h. Net CO assimilation rate, stomatal conduction, total carbon, its isotope signature and total sugar contents in leaves and roots were not significantly affected by the treatment and visible symptoms of foliar damage were not induced. Ozone exposure did not affect hydrogen peroxide and thiol contents but diminished the activities of glutathione reductase and dehydroascorbate reductase, stimulated the oxidation of ascorbate, and resulted in elevated total ascorbate contents. Total nitrogen, soluble protein and lignin contents remained unchanged upon ozone exposure, but the abundance of low molecular weight nitrogen (LMWN) compounds such as amino acids and nitrate as well as other anions were strongly diminished in leaves and roots. Other nitrogen pools did not benefit from the decline of LMWN, indicating reduced uptake and/or enhanced release of these compounds into the soil as a systemic response to aboveground ozone exposure. Several phenolic compounds, concurrent with fatty acids and stearyl alcohol, accumulated in leaves, but declined in roots, whereas total phenol contents significantly increased in the roots. Together these results indicate that local and systemic changes in both, primary and secondary metabolism contribute to the high tolerance of date palms to short-term acute ozone exposure. Date palms can grow and develop in an environment with high acute atmospheric ozone levels due to its tolerance to this air pollutant mediated by adaptations of both, primary and secondary metabolisms, as well as whole plant shoot-root interactions.
    Keywords: Sugars ; Reactive Oxygen Species ; Glutathione ; Ascorbate ; Nitrate ; Nitrogen Partitioning ; Anti-Oxidative System ; Secondary Metabolites ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 7
    Language: English
    In: Current Biology, 08 February 2016, Vol.26(3), pp.286-295
    Description: Carnivorous plants, such as the Venus flytrap ( ), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na -rich animal and nutrition for the plant. Children are able to count at the age of 15–18 months. In this work, Böhm et al. demonstrate that the carnivorous Venus flytrap plant is able to count as well. The leaf tips develop into snap traps, where the number of contacts of the prey with mechano-sensitive trap initiates capturing and processing of the animal victim.
    Keywords: Biology
    ISSN: 0960-9822
    E-ISSN: 1879-0445
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  • 8
    Language: English
    In: Current Biology, 09 September 2013, Vol.23(17), pp.1649-1657
    Description: Ammonium transporter (AMT/MEP/Rh) superfamily members mediate ammonium uptake and retrieval. This pivotal transport system is conserved among all living organisms. For plants, nitrogen represents a macronutrient available in the soil as ammonium, nitrate, and organic nitrogen compounds. Plants living on extremely nutrient-poor soils have developed a number of adaptation mechanisms, including a carnivorous lifestyle. This study addresses the molecular nature, function, and regulation of prey-derived ammonium uptake in the Venus flytrap, , one of the fastest active carnivores. The ammonium transporter DmAMT1 was localized in gland complexes where its expression was upregulated upon secretion. These clusters of cells decorating the inner trap surface are engaged in (1) secretion of an acidic digestive enzyme cocktail and (2) uptake of prey-derived nutrients. Voltage clamp of oocytes expressing DmAMT1 and membrane potential recordings with DmAMT1-expressing glands were used to monitor and compare electrophysiological properties of DmAMT1 in vitro and in planta. DmAMT1 exhibited the hallmark biophysical properties of a NH -selective channel. At depolarized membrane potentials (V  = 0), the K (3.2 ± 0.3 mM) indicated a low affinity of DmAMT1 for ammonium that increased systematically with negative going voltages. Upon hyperpolarization to, e.g., −200 mV, a K of 0.14 ± 0.015 mM documents the voltage-dependent shift of DmAMT1 into a NH transport system of high affinity. We suggest that regulation of glandular DmAMT1 and membrane potential readjustments of the endocrine cells provide for effective adaptation to varying, prey-derived ammonium sources.
    Keywords: Biology
    ISSN: 0960-9822
    E-ISSN: 1879-0445
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  • 9
    Language: English
    In: Plant physiology, June 2017, Vol.174(2), pp.798-814
    Description: Water limitation of plants causes stomatal closure to prevent water loss by transpiration. For this purpose, progressing soil water deficit is communicated from roots to shoots. Abscisic acid (ABA) is the key signal in stress-induced stomatal closure, but ABA as an early xylem-delivered signal is still a matter of debate. In this study, poplar plants () were exposed to water stress to investigate xylem sap sulfate and ABA, stomatal conductance, and sulfate transporter () expression. In addition, stomatal behavior and expression of ABA receptors, drought-responsive genes, transcription factors, and were studied after feeding sulfate and ABA to detached poplar leaves and epidermal peels of Arabidopsis (). The results show that increased xylem sap sulfate is achieved upon drought by reduced xylem unloading by PtaSULTR3;3a and PtaSULTR1;1, and by enhanced loading from parenchyma cells into the xylem via PtaALMT3b. Sulfate application caused stomatal closure in excised leaves and peeled epidermis. In the loss of sulfate-channel function mutant, At, sulfate-triggered stomatal closure was impaired. The QUAC1/ALMT12 anion channel heterologous expressed in oocytes was gated open by extracellular sulfate. Sulfate up-regulated the expression of , a key step of ABA synthesis, in guard cells. In conclusion, xylem-derived sulfate seems to be a chemical signal of drought that induces stomatal closure via QUAC1/ALMT12 and/or guard cell ABA synthesis.
    Keywords: Abscisic Acid -- Biosynthesis ; Arabidopsis Proteins -- Metabolism ; Organic Anion Transporters -- Metabolism ; Plant Stomata -- Physiology ; Sulfates -- Metabolism ; Xylem -- Metabolism
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 10
    In: New Phytologist, February 2015, Vol.205(3), pp.1320-1329
    Description: Carnivorous Dionaea muscipula operates active snap traps for nutrient acquisition from prey; so what is the role of D. muscipula's reduced root system? We studied the capacity for nitrogen (N) acquisition via traps, and its effect on plant allometry; the capacity of roots to absorb NO3−, NH4+ and glutamine from the soil solution; and the fate and interaction of foliar‐ and root‐acquired N. Feeding D. muscipula snap traps with insects had little effect on the root : shoot ratio, but promoted petiole relative to trap growth. Large amounts of NH4+ and glutamine were absorbed upon root feeding. The high capacity for root N uptake was maintained upon feeding traps with glutamine. High root acquisition of NH4+ was mediated by 2.5‐fold higher expression of the NH4+ transporter DmAMT1 in the roots compared with the traps. Electrophysiological studies confirmed a high constitutive capacity for NH4+ uptake by roots. Glutamine feeding of traps inhibited the influx of 15N from root‐absorbed 15N/13C‐glutamine into these traps, but not that of 13C. Apparently, fed traps turned into carbon sinks that even acquired organic carbon from roots. N acquisition at the whole‐plant level is fundamentally different in D. muscipula compared with noncarnivorous species, where foliar N influx down‐regulates N uptake by roots.
    Keywords: Ammonium ; Glutamine ; Nitrogen N Nutrition ; Plant Carnivory ; Root : shoot Integration
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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