Publications by authors named "Joachim Fisahn"

37 Publications

RAPTOR Controls Developmental Growth Transitions by Altering the Hormonal and Metabolic Balance.

Plant Physiol 2018 06 23;177(2):565-593. Epub 2018 Apr 23.

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.

Vegetative growth requires the systemic coordination of numerous cellular processes, which are controlled by regulatory proteins that monitor extracellular and intracellular cues and translate them into growth decisions. In eukaryotes, one of the central factors regulating growth is the serine/threonine protein kinase Target of Rapamycin (TOR), which forms complexes with regulatory proteins. To understand the function of one such regulatory protein, Regulatory-Associated Protein of TOR 1B (RAPTOR1B), in plants, we analyzed the effect of mutations on growth and physiology in Arabidopsis () by detailed phenotyping, metabolomic, lipidomic, and proteomic analyses. Mutation of resulted in a strong reduction of TOR kinase activity, leading to massive changes in central carbon and nitrogen metabolism, accumulation of excess starch, and induction of autophagy. These shifts led to a significant reduction of plant growth that occurred nonlinearly during developmental stage transitions. This phenotype was accompanied by changes in cell morphology and tissue anatomy. In contrast to previous studies in rice (), we found that the Arabidopsis mutation did not affect chloroplast development or photosynthetic electron transport efficiency; however, it resulted in decreased CO assimilation rate and increased stomatal conductance. The mutants also had reduced abscisic acid levels. Surprisingly, abscisic acid feeding experiments resulted in partial complementation of the growth phenotypes, indicating the tight interaction between TOR function and hormone synthesis and signaling in plants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.17.01711DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001337PMC
June 2018

Control of plant leaf movements by the lunisolar tidal force.

Authors:
Joachim Fisahn

Ann Bot 2018 06;121(7):e1-e6

Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Potsdam, Germany.

Background: Investigations into the diurnal ascent and descent of leaves of beans and other species, as well as experimental interventions into these movements, such as exposures to light at different times during the movement cycle, led to the concept of an endogenous 'clock' as a regulator of these oscillations. The causal origin of leaf movement can be traced to processes that modulate cell volume in target tissues of the pulvinus and petiole. However, these elements of the leaf-movement process do not sufficiently account for the rhythms that are generated following germination in constant light or dark conditions, or when plants are transferred to similar free-running conditions.

Scope: To further unravel the regulation of leaf-movement rhythms, many of the published time courses of leaf movements that provided evidence for the concept of the endogenous clock were analysed in conjunction with the contemporaneous time courses of the lunisolar tidal acceleration. This was accomplished by application of the Etide program, which estimates, with high temporal resolution, local gravitational changes as a consequence of the diurnal variations of the lunisolar gravitational force due to the orbits and relative positions of Earth, Moon and Sun. To substantiate the results obtained in earthbound laboratories additional experiments were performed in the International Space Station (ISS). Tidal recurrence within the ISS exhibited a periodicity of 45 min. In all instances investigated, it was evident that a synchronism exists between the times of the turning points of both the lunisolar tide and of the leaftide when the direction of leaf movement changes. This finding of synchrony documents that the lunisolar tide is a regulator of the leaftide, and that the rhythm of leaf movement is not of endogenous origin but is an expression of an exogenous lunisolar clock impressed upon the leaf-movement apparatus.

Conclusions: A huge number of correlations between leaftide and Etide time courses were established for leaf movement rhythms in natural conditions of the greenhouse, in conditions of constant light or dark, and under the microgravity conditions of the International Space Station. Even the apparently spontaneous short-period, small-amplitude rhythms recorded from leaves under unusual growth conditions are consistent with the hypothesis of a lunisolar zeitgeber. Synchronism between leaftide and Etide is discussed in terms of classical and quantum mechanics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mcx214DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6007428PMC
June 2018

Are there tides within trees?

Authors:
Joachim Fisahn

Ann Bot 2018 11;122(5):735-739

Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany.

Background: Tree stem diameters and electrical stem potentials exhibit rhythmic variations with periodicities of 24-25 h. Under free-running conditions of constant light or darkness these rhythms were suggested to be mediated by the lunisolar gravitational force.

Scope: To further unravel the regulation of tree stem diameter dilatations, many of the published time courses of diameter variations were re-evaluated in conjunction with the contemporaneous time courses of the lunisolar tidal acceleration. This was accomplished by application of the Etide program, which estimates, with high temporal resolution, local gravitational changes as a consequence of the diurnal variations of the lunisolar gravitational force due to the orbits and relative positions of Earth, Moon and Sun. In all instances investigated, it was evident that a synchronism exists between the times of the turning points of both the lunisolar tide and stem diameter variations when the direction of extension changes. This finding of synchrony documents that the lunisolar tide is a regulator of the tree stem diameter dilatations.

Conclusions: Under the described experimental conditions, rhythms in tree stem diameter dilations and electrical stem potentials are controlled by the lunisolar gravitational acceleration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mcx215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6215047PMC
November 2018

A proposal to explain how the circatidal rhythm of the Arabidopsis thaliana root elongation rate could be mediated by the lunisolar gravitational force: a quantum physical approach.

Ann Bot 2018 11;122(5):725-733

Institute of Physics, University of the Federal Armed Forces, Neubiberg, Germany.

Background And Aims: Roots of Arabidopsis thaliana exhibit a 24.8 h oscillation of elongation rate when grown under free-running conditions. This growth rhythm is synchronized with the time course of the local lunisolar tidal acceleration. The present study aims at a physiological/physical model to describe the interaction of weak gravitational fields with cellular water dynamics that mediate rhythmic root growth profiles.

Methods: Fundamental physical laws are applied to model the water dynamics within single plant cells in an attempt to mimic the 24.8 h oscillations in root elongation growth. In particular, a quantum gravitational description of the time course in root elongation is presented, central to which is the formation of coherent assemblies of mass due to the lunisolar gravitational field. Mathematical equations that characterize lunisolar gravity-induced coherent assemblies of water molecules are derived and related to the mass of cellular water within roots of A. thaliana.

Key Results: The derived physical model of gravitationally modulated water assemblies is capable of accounting for the experimentally observed arabidopsis root growth kinetics under free-running conditions. The close analogy between the derived time-dependent lunisolar effect upon coherent molecular states of water within single cells and the coherent assemblies of electrons that characterize the quantum Hall effect is emphasized.

Conclusions: The dynamics of the lunisolar-induced variation in coherent water assemblies provide a possible mechanism to describe the observed 24.8 h oscillation of root growth rate of A. thaliana. Therefore, this mechanism could function as an independent timekeeper to control cell elongation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mcx143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6215034PMC
November 2018

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana.

Plant Signal Behav 2015 ;10(9):e1057367

c School of Biological Sciences; University of Bristol ; Bristol , UK.

The yield of chlorophyll fluorescence Ft was measured in leaves of Arabidopsis thaliana over periods of several days under conditions of continuous illumination (LL) without the application of saturating light pulses. After linearization of the time series of the chlorophyll fluorescence yield (ΔFt), oscillations became apparent with periodicities in the circatidal range. Alignments of these linearized time series ΔFt with the lunisolar tidal acceleration revealed high degrees of synchrony and phase congruence. Similar congruence with the lunisolar tide was obtained with the linearized quantum yield of PSII (ΔФII), recorded after application of saturating light pulses. These findings strongly suggest that there is an exogenous timekeeper which is a stimulus for the oscillations detected in both the linearized yield of chlorophyll fluorescence (ΔFt) and the linearized quantum yield of PSII (ΔФII).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/15592324.2015.1057367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4883933PMC
June 2016

Lunar gravity affects leaf movement of Arabidopsis thaliana in the International Space Station.

Planta 2015 Jun 21;241(6):1509-18. Epub 2015 Mar 21.

Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg1, 14476, Potsdam, Germany,

Main Conclusion: Cyclic leaf ascent and descent occur in synchrony and phase congruence with the lunisolar tidal force under a broad range of conditions. Digitized records of the vertical leaf movements of Arabidopsis thaliana were collected under space flight conditions in the International Space Station (ISS). Oscillations of leaf movements with periods of 45 and 90 min were found under light-adapted conditions, whereas in darkness, the periods were 45, 90, and 135 min. To demonstrate the close relationship between these oscillations and cyclical variations of the lunisolar gravitational force, we estimated the oscillations of the in-orbit lunisolar tide as they apply to the ISS, with the aid of the Etide software application. In general, in-orbit lunisolar gravitational profiles exhibited a periodicity of 45 min. Alignment of these in-orbit oscillations with the oscillations of Arabidopsis leaf movement revealed high degrees of synchrony and a congruence of phase. These data corroborate previous results which suggested a correlative relationship and a possible causal link between leaf movement rhythms obtained on ground and the rhythmic variation of the lunisolar tidal force.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00425-015-2280-xDOI Listing
June 2015

Sulphate fertilization ameliorates long-term aluminum toxicity symptoms in perennial ryegrass (Lolium perenne).

Plant Physiol Biochem 2014 Oct 30;83:88-99. Epub 2014 Jul 30.

Center of Plant-Soil Interaction and Natural Resources Biotechnology, Scientific and Technological Bioresource Nucleus (BIOREN), Universidad de La Frontera, Temuco, Chile.

Effects of the oxanion sulphate on plant aluminum (Al(3+)) detoxification mechanisms are not well understood. Therefore, holistic physiological and biochemical modifications induced by progressively increased doses of sulphate fertilization in the presence of long-term Al(3+) stress were investigated in the aluminum sensitive perennial ryegrass (Lolium perenne L. cvJumbo). Plant growth inhibition induced by Al(3+) was decreased in response to increasing doses of sulphate supply. Aluminum concentrations measured in roots of perennial ryegrass by atomic absorption spectrometry declined significantly with increasing sulphate concentrations. In parallel, we determined a rise of sulphur in shoots and roots of perennial ryegrass. Inclusion of up to 360 μM of sulphate enhanced cysteine and glutathione biosynthesis in Al(3+) (1.07 μM) treated plants. This increase of thiol-containing compounds favored all modifications in the glutathione redox balance, declining lipid peroxidation, decreasing the activity of superoxide dismutase, and modifying the expression of proteins involved in the diminution of Al(3+) toxicity in roots. In particular, proteome analysis by 1D-SDS-PAGE and LC-MS/MS allowed to identify up (e.g. vacuolar proton ATPase, proteosome β subunit, etc) and down (Glyoxilase I, Ascorbate peroxidase, etc.) regulated proteins induced by Al(3+) toxicity symptoms in roots. Although, sulphate supply up to 480 μM caused a reduction in Al(3+) toxicity symptoms, it was not as efficient as compared to 360 μM sulphate fertilization. These results suggest that sulphate fertilization ameliorates Al(3+) toxicity responses in an intracellular specific manner within Lolium perenne.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.plaphy.2014.07.017DOI Listing
October 2014

Expression of Sucrose Transporter cDNAs Specifically in Companion Cells Enhances Phloem Loading and Long-Distance Transport of Sucrose but Leads to an Inhibition of Growth and the Perception of a Phosphate Limitation.

Plant Physiol 2014 Jun 28;165(2):715-731. Epub 2014 Apr 28.

Department of Biological Sciences, University of North Texas, Denton, Texas 76203 (K.D., A.S.K., B.G.A.);Max Planck Institute of Molecular Plant Physiology, D-14476 Potsdam-Golm, Germany (R.S., J.F., M.S.); andThe Samuel Roberts Noble Foundation, Plant Biology Division, Ardmore, Oklahoma 73401 (B.P., W.-R.S.)

Sucrose (Suc) is the predominant form of carbon transported through the phloem from source to sink organs and is also a prominent sugar for short-distance transport. In all streptophytes analyzed, Suc transporter genes (SUTs or SUCs) form small families, with different subgroups evolving distinct functions. To gain insight into their capacity for moving Suc in planta, representative members of each clade were first expressed specifically in companion cells of Arabidopsis (Arabidopsis thaliana) and tested for their ability to rescue the phloem-loading defect caused by the Suc transporter mutation, Atsuc2-4. Sequence similarity was a poor indicator of ability: Several genes with high homology to AtSUC2, some of which have phloem-loading functions in other eudicot species, did not rescue the Atsuc2-4 mutation, whereas a more distantly related gene, ZmSUT1 from the monocot Zea mays, did restore phloem loading. Transporter complementary DNAs were also expressed in the companion cells of wild-type Arabidopsis, with the aim of increasing productivity by enhancing Suc transport to growing sink organs and reducing Suc-mediated feedback inhibition on photosynthesis. Although enhanced Suc loading and long-distance transport was achieved, growth was diminished. This growth inhibition was accompanied by increased expression of phosphate (P) starvation-induced genes and was reversed by providing a higher supply of external P. These experiments suggest that efforts to increase productivity by enhancing sugar transport may disrupt the carbon-to-P homeostasis. A model for how the plant perceives and responds to changes in the carbon-to-P balance is presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.114.238410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4044860PMC
June 2014

NAC transcription factor speedy hyponastic growth regulates flooding-induced leaf movement in Arabidopsis.

Plant Cell 2013 Dec 20;25(12):4941-55. Epub 2013 Dec 20.

University of Potsdam, Institute of Biochemistry and Biology, 14476 Potsdam, Germany.

In rosette plants, root flooding (waterlogging) triggers rapid upward (hyponastic) leaf movement representing an important architectural stress response that critically determines plant performance in natural habitats. The directional growth is based on localized longitudinal cell expansion at the lower (abaxial) side of the leaf petiole and involves the volatile phytohormone ethylene (ET). We report the existence of a transcriptional core unit underlying directional petiole growth in Arabidopsis thaliana, governed by the NAC transcription factor speedy hyponastic growth (SHYG). Overexpression of SHYG in transgenic Arabidopsis thaliana enhances waterlogging-triggered hyponastic leaf movement and cell expansion in abaxial cells of the basal petiole region, while both responses are largely diminished in shyg knockout mutants. Expression of several expansin and xyloglucan endotransglycosylase/hydrolase genes encoding cell wall-loosening proteins was enhanced in SHYG overexpressors but lowered in shyg. We identified ACC oxidase5 (ACO5), encoding a key enzyme of ET biosynthesis, as a direct transcriptional output gene of SHYG and found a significantly reduced leaf movement in response to root flooding in aco5 T-DNA insertion mutants. Expression of SHYG in shoot tissue is triggered by root flooding and treatment with ET, constituting an intrinsic ET-SHYG-ACO5 activator loop for rapid petiole cell expansion upon waterlogging.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.113.117861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3903997PMC
December 2013

Swarms, swarming and entanglements of fungal hyphae and of plant roots.

Commun Integr Biol 2013 Sep 21;6(5):e25299. Epub 2013 Jun 21.

School of Biological Sciences; University of Bristol; Bristol, United Kingdom.

There has been recent interest in the possibility that plant roots can show oriented collective motion, or swarming behavior. We examine the evidence supportive of root swarming and we also present new observations on this topic. Seven criteria are proposed for the definition of a swarm, whose application can help identify putative swarming behavior in plants. Examples where these criteria are fulfilled, at many levels of organization, are presented in relation to plant roots and root systems, as well as to the root-like mycelial cords (rhizomorphs) of fungi. The ideas of both an "active" swarming, directed by a signal which imposes a common vector on swarm element aggregation, and a "passive" swarming, where aggregation results from external constraint, are introduced. Active swarming is a pattern of cooperative behavior peculiar to the sporophyte generation of vascular plants and is the antithesis of the competitive behavior shown by the gametophyte generation of such plants, where passive swarming may be found. Fungal mycelial cords could serve as a model example of swarming in a multi-cellular, non-animal system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4161/cib.25299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3829901PMC
September 2013

Salt-responsive ERF1 regulates reactive oxygen species-dependent signaling during the initial response to salt stress in rice.

Plant Cell 2013 Jun 25;25(6):2115-31. Epub 2013 Jun 25.

Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany.

Early detection of salt stress is vital for plant survival and growth. Still, the molecular processes controlling early salt stress perception and signaling are not fully understood. Here, we identified salt-responsive ERF1 (SERF1), a rice (Oryza sativa) transcription factor (TF) gene that shows a root-specific induction upon salt and hydrogen peroxide (H2O2) treatment. Loss of SERF1 impairs the salt-inducible expression of genes encoding members of a mitogen-activated protein kinase (MAPK) cascade and salt tolerance-mediating TFs. Furthermore, we show that SERF1-dependent genes are H2O2 responsive and demonstrate that SERF1 binds to the promoters of MAPK kinase kinase6 (MAP3K6), MAPK5, dehydration-responsive element bindinG2A (DREB2A), and zinc finger protein179 (ZFP179) in vitro and in vivo. SERF1 also directly induces its own gene expression. In addition, SERF1 is a phosphorylation target of MAPK5, resulting in enhanced transcriptional activity of SERF1 toward its direct target genes. In agreement, plants deficient for SERF1 are more sensitive to salt stress compared with the wild type, while constitutive overexpression of SERF1 improves salinity tolerance. We propose that SERF1 amplifies the reactive oxygen species-activated MAPK cascade signal during the initial phase of salt stress and translates the salt-induced signal into an appropriate expressional response resulting in salt tolerance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.113.113068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3723616PMC
June 2013

Arabidopsis thaliana root elongation growth is sensitive to lunisolar tidal acceleration and may also be weakly correlated with geomagnetic variations.

Ann Bot 2013 May 26;111(5):859-72. Epub 2013 Mar 26.

School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.

Background: Correlative evidence suggests a relationship between the lunisolar tidal acceleration and the elongation rate of arabidopsis roots grown under free-running conditions of constant low light.

Methods: Seedlings of Arabidopsis thaliana were grown in a controlled-climate chamber maintained at a constant temperature and subjected to continuous low-level illumination from fluorescent tubes, conditions that approximate to a 'free-running' state in which most of the abiotic factors that entrain root growth rates are excluded. Elongation of evenly spaced, vertical primary roots was recorded continuously over periods of up to 14 d using high temporal- and spatial-resolution video imaging and were analysed in conjunction with geophysical variables.

Key Results And Conclusions: The results confirm the lunisolar tidal/root elongation relationship. Also presented are relationships between the hourly elongation rates and the contemporaneous variations in geomagnetic activity, as evaluated from the disturbance storm time and ap indices. On the basis of time series of root elongation rates that extend over ≥4 d and recorded at different seasons of the year, a provisional conclusion is that root elongation responds to variation in the lunisolar force and also appears to adjust in accordance with variations in the geomagnetic field. Thus, both lunisolar tidal acceleration and the geomagnetic field should be considered as modulators of root growth rate, alongside other, stronger and more well-known abiotic environmental regulators, and perhaps unexplored factors such as air ions. Major changes in atmospheric pressure are not considered to be a factor contributing to oscillations of root elongation rate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mct052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3631336PMC
May 2013

High-throughput phenotyping of root growth dynamics.

Methods Mol Biol 2012 ;918:21-40

Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany.

Plant organ phenotyping by noninvasive video imaging techniques provides a powerful tool to assess physiological traits, circadian and diurnal rhythms, and biomass production. In particular, growth of individual plant organs is known to exhibit a high plasticity and occurs as a result of the interaction between various endogenous and environmental processes. Thus, any investigation aiming to unravel mechanisms that determine plant or organ growth has to accurately control and document the environmental growth conditions. Here we describe challenges in establishing a recently developed plant root monitoring platform (PlaRoM) specially suited for noninvasive high-throughput plant growth analysis with highest emphasis on the detailed documentation of capture time, as well as light and temperature conditions. Furthermore, we discuss the experimental procedure for measuring root elongation kinetics and key points that must be considered in such measurements. PlaRoM consists of a robotized imaging platform enclosed in a custom designed phytochamber and a root extension profiling software application. This platform has been developed for multi-parallel recordings of root growth phenotypes of up to 50 individual seedlings over several days, with high spatial and temporal resolution. Two Petri dishes are mounted on a vertical sample stage in a custom designed phytochamber that provides exact temperature control. A computer-controlled positioning unit moves these Petri dishes in small increments and enables continuous screening of the surface under a binocular microscope. Detection of the root tip is achieved by applying thresholds on image pixel data and verifying the neighbourhood for each dark pixel. The growth parameters are visualized as position over time or growth rate over time graphs and averaged over consecutive days, light-dark periods and 24 h day periods. This setup enables the investigation of root extension profiles of different genotypes in various growth conditions (e.g., light protocol, temperature, growth media) and is especially suited for the detection of diurnal or circadian growth rhythms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-61779-995-2_3DOI Listing
December 2012

Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.

New Phytol 2012 Jul 14;195(2):346-355. Epub 2012 May 14.

School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.

• All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1469-8137.2012.04162.xDOI Listing
July 2012

Lunisolar tidal force and the growth of plant roots, and some other of its effects on plant movements.

Ann Bot 2012 Jul 20;110(2):301-18. Epub 2012 Mar 20.

School of Biological Sciences, University of Bristol, Bristol, UK.

Background: Correlative evidence has often suggested that the lunisolar tidal force, to which the Sun contributes 30 % and the Moon 60 % of the combined gravitational acceleration, regulates a number of features of plant growth upon Earth. The time scales of the effects studied have ranged from the lunar day, with a period of approx. 24.8 h, to longer, monthly or seasonal variations.

Scope: We review evidence for a lunar involvement with plant growth. In particular, we describe experimental observations which indicate a putative lunar-based relationship with the rate of elongation of roots of Arabidopsis thaliana maintained in constant light. The evidence suggests that there may be continuous modulation of root elongation growth by the lunisolar tidal force. In order to provide further supportive evidence for a more general hypothesis of a lunisolar regulation of growth, we highlight similarly suggestive evidence from the time courses of (a) bean leaf movements obtained from kymographic observations; (b) dilatation cycles of tree stems obtained from dendrograms; and (c) the diurnal changes of wood-water relationships in a living tree obtained by reflectometry.

Conclusions: At present, the evidence for a lunar or a lunisolar influence on root growth or, indeed, on any other plant system, is correlative, and therefore circumstantial. Although it is not possible to alter the lunisolar gravitational force experienced by living organisms on Earth, it is possible to predict how this putative lunisolar influence will vary at times in the near future. This may offer ways of testing predictions about possible Moon-plant relationships. As for a hypothesis about how the three-body system of Earth-Sun-Moon could interact with biological systems to produce a specific growth response, this remains a challenge for the future. Plant growth responses are mainly brought about by differential movement of water across protoplasmic membranes in conjunction with water movement in the super-symplasm. It may be in this realm of water movements, or even in the physical forms which water adopts within cells, that the lunisolar tidal force has an impact upon living growth systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mcs038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3394636PMC
July 2012

NFX1-LIKE2 (NFXL2) suppresses abscisic acid accumulation and stomatal closure in Arabidopsis thaliana.

PLoS One 2011 3;6(11):e26982. Epub 2011 Nov 3.

University of Potsdam, Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany.

The NFX1-LIKE1 (NFXL1) and NFXL2 genes were identified as regulators of salt stress responses. The NFXL1 protein is a nuclear factor that positively affects adaptation to salt stress. The nfxl1-1 loss-of-function mutant displayed reduced survival rates under salt and high light stress. In contrast, the nfxl2-1 mutant, defective in the NFXL2 gene, and NFXL2-antisense plants exhibited enhanced survival under these conditions. We show here that the loss of NFXL2 function results in abscisic acid (ABA) overaccumulation, reduced stomatal conductance, and enhanced survival under drought stress. The nfxl2-1 mutant displayed reduced stomatal aperture under all conditions tested. Fusicoccin treatment, exposition to increasing light intensities, and supply of decreasing CO(2) concentrations demonstrated full opening capacity of nfxl2-1 stomata. Reduced stomatal opening presumably is a consequence of elevated ABA levels. Furthermore, seedling growth, root growth, and stomatal closure were hypersensitive to exogenous ABA. The enhanced ABA responses may contribute to the improved drought stress resistance of the mutant. Three NFXL2 splice variants were cloned and named NFXL2-78, NFXL2-97, and NFXL2-100 according to the molecular weight of the putative proteins. Translational fusions to the green fluorescent protein suggest nuclear localisation of the NFXL2 proteins. Stable expression of the NFXL2-78 splice variant in nfxl2-1 plants largely complemented the mutant phenotype. Our data show that NFXL2 controls ABA levels and suppresses ABA responses. NFXL2 may prevent unnecessary and costly stress adaptation under favourable conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0026982PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3207813PMC
March 2012

Tomato fruit photosynthesis is seemingly unimportant in primary metabolism and ripening but plays a considerable role in seed development.

Plant Physiol 2011 Dec 4;157(4):1650-63. Epub 2011 Oct 4.

Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.

Fruit of tomato (Solanum lycopersicum), like those from many species, have been characterized to undergo a shift from partially photosynthetic to truly heterotrophic metabolism. While there is plentiful evidence for functional photosynthesis in young tomato fruit, the rates of carbon assimilation rarely exceed those of carbon dioxide release, raising the question of its role in this tissue. Here, we describe the generation and characterization of lines exhibiting a fruit-specific reduction in the expression of glutamate 1-semialdehyde aminotransferase (GSA). Despite the fact that these plants contained less GSA protein and lowered chlorophyll levels and photosynthetic activity, they were characterized by few other differences. Indeed, they displayed almost no differences in fruit size, weight, or ripening capacity and furthermore displayed few alterations in other primary or intermediary metabolites. Although GSA antisense lines were characterized by significant alterations in the expression of genes associated with photosynthesis, as well as with cell wall and amino acid metabolism, these changes were not manifested at the phenotypic level. One striking feature of the antisense plants was their seed phenotype: the transformants displayed a reduced seed set and altered morphology and metabolism at early stages of fruit development, although these differences did not affect the final seed number or fecundity. Taken together, these results suggest that fruit photosynthesis is, at least under ambient conditions, not necessary for fruit energy metabolism or development but is essential for properly timed seed development and therefore may confer an advantage under conditions of stress.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.111.186874DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3327185PMC
December 2011

Mutations in leaf starch metabolism modulate the diurnal root growth profiles of Arabidopsis thaliana.

Plant Signal Behav 2011 Jul;6(7):995-8

Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany.

Roots of Arabidopsis thaliana exhibit stable diurnal growth profiles that are controlled by the circadian clock. Here we describe the effects of mutations in leaf starch metabolism on the diurnal root growth characteristics of Arabidopsis thaliana. High temporal and spatial resolution video imaging was performed to quantify the growth kinetics of Arabidopsis wild-type as well as pgm, sex1, mex1, dpe1 and dpe2 starch metabolism mutants grown in three different photoperiods. As a result, root growth patterns of all genotypes displayed characteristic modifications in their diurnal kinetics that were also affected by the photoperiod. To further investigate the role of starch derived substrate deficiency on root growth, the effect of 0.05% extracellular sucrose was studied in 12 h-12 h light-dark cycles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4161/psb.6.7.15484DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257776PMC
July 2011

Circadian control of root elongation and C partitioning in Arabidopsis thaliana.

Plant Cell Environ 2011 Jun 24;34(6):877-894. Epub 2011 Mar 24.

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam/Golm, Am Mühlenberg 1, GermanyDepartment of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich NR4/UH, UK.

Plants grow in a light/dark cycle. We have investigated how growth is buffered against the resulting changes in the carbon supply. Growth of primary roots of Arabidopsis seedlings was monitored using time-resolved video imaging. The average daily rate of growth is increased in longer light periods or by addition of sugars. It responds slowly over days when the conditions are changed. The momentary rate of growth exhibits a robust diel oscillation with a minimum 8-9 h after dawn and a maximum towards the end of the night. Analyses with starch metabolism mutants show that starch turnover is required to maintain growth at night. A carbon shortfall leads to an inhibition of growth, which is not immediately reversed when carbon becomes available again. The diel oscillation persists in continuous light and is strongly modified in clock mutants. Central clock functions that depend on CCA1/LHY are required to set an appropriate rate of starch degradation and maintain a supply of carbon to support growth through to dawn, whereas ELF3 acts to decrease growth in the light period and promote growth in the night. Thus, while the overall growth rate depends on the carbon supply, the clock orchestrates diurnal carbon allocation and growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-3040.2011.02286.xDOI Listing
June 2011

Proteomics - The key to understanding systems biology of Arabidopsis trichomes.

Phytochemistry 2011 Jul 15;72(10):1061-70. Epub 2010 Oct 15.

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany.

Every multicellular organism consists of numerous organs, tissues and specific cell types. To gain detailed knowledge about the morphogenesis of these complex structures, it is inevitable to advance biochemical analyses to ultimate spatial and temporal resolution since individual cell types contribute differently to the overall performance of living objects. Single cell sampling combined with systems biological approaches was recently applied to investigations of Arabidopsis thaliana trichomes (leaf hairs). These are single celled structures that provide ideal model systems to address various aspects of plant cell development and differentiation at the level of individual cells. A previously suggested function of trichomes in plant stress responses could thus be confirmed. Furthermore, trichome-specific "omics" data collected in several laboratories are mutually conclusive which demonstrates the applicability of systems biological approaches at the single cell level.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.phytochem.2010.09.003DOI Listing
July 2011

Photosynthesis and metabolism interact during acclimation of Arabidopsis thaliana to high irradiance and sulphur depletion.

Plant Cell Environ 2010 Nov;33(11):1974-88

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.

Arabidopsis plants were exposed to high light or sulphur depletion alone or in combination for 6 d, and changes of photosynthetic parameters and metabolite abundances were quantified. Photosynthetic electron transport rates (ETRs) of plants exposed to sulphur depletion and high light decreased strongly at day 2 of the acclimation period. After 3 d of treatment, the photosynthetic capacity recovered in plants exposed to the combined stresses, indicating a short recovery time for re-adjustment of photosynthesis. However, at metabolic level, the stress combination had a profound effect on central metabolic pathways such as the tricarboxylic acid (TCA) cycle, glycolysis, pentose phosphate cycle and large parts of amino acid metabolism. Under these conditions, central metabolites, such as sugars and their phosphates, increased, while sulphur-containing compounds were decreased. Further differential responses were found for the stress indicator proline accumulating already at day 1 of the high-light regime, but in combination with sulphur depletion first declined and after a recovery phase reached a delayed elevated level. Other metabolites such as raffinose and putrescine seem to replace proline during the early combinatorial stress response and may act as alternative protectants. Our findings support the notion that plants integrate the selectively sensed stress factors in central metabolism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-3040.2010.02199.xDOI Listing
November 2010

Analysis of Arabidopsis thaliana root growth kinetics with high temporal and spatial resolution.

Ann Bot 2010 May;105(5):783-91

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany.

Background: Methods exist to quantify the distribution of growth rate over the root axis. However, non-destructive, high-throughput evaluations of total root elongation in controlled environments and the field are lacking in growth studies. A new imaging approach to analyse total root elongation is described.

Scope: High pixel resolution of the images enables the study of growth in short time intervals and provides high temporal resolution. Using the method described, total root elongation rates are calculated from the displacement of the root tip. Although the absolute root elongation rate changes in response to growth conditions, this set-up enables root growth of Arabidopsis wild-type seedlings to be followed for more than 1 month after germination. The method provides an easy approach to decipher root extension rate and much simpler calculations compared with other methods that use segmental growth to address this question.

Conclusions: The high temporal resolution allows small modifications of total root elongation growth to be revealed. Furthermore, with the options to investigate growth of various mutants in diverse growth conditions the present tool allows modulations in root growth kinetics due to different biotic and abiotic stimuli to be unravelled. Measurements performed on Arabidopsis thaliana wild-type (Col0) plants revealed rhythms superimposed on root elongation. Results obtained from the starchless mutant pgm, however, present a clearly modified pattern. As expected, deviation is strongest during the dark period.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/aob/mcq048DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2859919PMC
May 2010

Metabolic profiling of Arabidopsis thaliana epidermal cells.

J Exp Bot 2010 Mar 11;61(5):1321-35. Epub 2010 Feb 11.

Max-Planck-Institute of Molecular Plant Physiology, Campus Golm, Am Mühlenberg 1, D-14476 Potsdam OT Golm, Germany.

Metabolic phenotyping at cellular resolution may be considered one of the challenges in current plant physiology. A method is described which enables the cell type-specific metabolic analysis of epidermal cell types in Arabidopsis thaliana pavement, basal, and trichome cells. To achieve the required high spatial resolution, single cell sampling using microcapillaries was combined with routine gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) based metabolite profiling. The identification and relative quantification of 117 mostly primary metabolites has been demonstrated. The majority, namely 90 compounds, were accessible without analytical background correction. Analyses were performed using cell type-specific pools of 200 microsampled individual cells. Moreover, among these identified metabolites, 38 exhibited differential pool sizes in trichomes, basal or pavement cells. The application of an independent component analysis confirmed the cell type-specific metabolic phenotypes. Significant pool size changes between individual cells were detectable within several classes of metabolites, namely amino acids, fatty acids and alcohols, alkanes, lipids, N-compounds, organic acids and polyhydroxy acids, polyols, sugars, sugar conjugates and phenylpropanoids. It is demonstrated here that the combination of microsampling and GC-MS based metabolite profiling provides a method to investigate the cellular metabolism of fully differentiated plant cell types in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jxb/erq002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2837255PMC
March 2010

Quantitative expression analysis of selected transcription factors in pavement, basal and trichome cells of mature leaves from Arabidopsis thaliana.

Protoplasma 2010 May 26;241(1-4):29-36. Epub 2010 Jan 26.

Max-Planck-Institut fuer Molekulare Pflanzenphysiologie, Am Muehlenberg 1, 14476 Potsdam, Germany.

Gene expression levels of several transcription factors from Arabidopsis thaliana that were described previously to be involved in leaf development and trichome formation were analysed in trichome, basal and pavement cells of mature leaves. Single cell samples of these three cells types were collected by glass micro-capillaries. Real-time reverse transcription (RT)-PCR was used to analyse expression patterns of the following transcription factors: MYB23, MYB55, AtHB1, FILAMENTOUS FLOWER (FIL)/YABBY1 (YAB1), TRIPTYCHON (TRY) and CAPRICE (CPC). A difference in the expression patterns of TRY and CPC was revealed. Contrary to the CPC expression pattern, no transcripts of TRY could be detected in pavement cells. FIL/YAB1 was exclusively expressed in trichome cells. AtHB1 was highly expressed throughout all three cell types. MYB55 was higher expressed in basal cells than in trichome and pavement cells. MYB23 showed a pattern of low expression in pavement cells, medium in basal cells and high expression in trichomes. Expression patterns obtained by single cell sampling and real-time RT-PCR were compared to promoter GUS fusions of the selected transcription factors. Therefore, we regenerated two transgenic Arabidopsis lines that expressed the GUS reporter gene under control of the promoters of MYB55 and YAB1. In conclusion, despite their function in leaf morphogenesis, all six transcription factors were detected in mature leaves. Furthermore, single cell sampling and promoter GUS staining patterns demonstrated the predominant presence of MYB55 in basal cells as compared to pavement cells and trichomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00709-009-0099-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856857PMC
May 2010

High throughput phenotyping of root growth dynamics, lateral root formation, root architecture and root hair development enabled by PlaRoM.

Funct Plant Biol 2009 Nov;36(11):938-946

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam Golm, Germany.

Plant organ phenotyping by non-invasive video imaging techniques provides a powerful tool to assess physiological traits and biomass production. We describe here a range of applications of a recently developed plant root monitoring platform (PlaRoM). PlaRoM consists of an imaging platform and a root extension profiling software application. This platform has been developed for multi parallel recordings of root growth phenotypes of up to 50 individual seedlings over several days, with high spatial and temporal resolution. PlaRoM can investigate root extension profiles of different genotypes in various growth conditions (e.g. light protocol, temperature, growth media). In particular, we present primary root growth kinetics that was collected over several days. Furthermore, addition of 0.01% sucrose to the growth medium provided sufficient carbohydrates to maintain reduced growth rates in extended nights. Further analysis of records obtained from the imaging platform revealed that lateral root development exhibits similar growth kinetics to the primary root, but that root hairs develop in a faster rate. The compatibility of PlaRoM with currently accessible software packages for studying root architecture will be discussed. We are aiming for a global application of our collected root images to analytical tools provided in remote locations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1071/FP09167DOI Listing
November 2009

Protein profiling of single epidermal cell types from Arabidopsis thaliana using surface-enhanced laser desorption and ionization technology.

J Plant Physiol 2008 Aug 18;165(12):1227-37. Epub 2008 Apr 18.

Max-Planck-Institute of Molecular Plant Physiology, 14776 Potsdam OT Golm, Germany.

Here, we describe a novel approach for investigating differential protein expression within three epidermal cell types. In particular, 3000 single pavement, basal, and trichome cells from leaves of Arabidopsis thaliana were harvested by glass micro-capillaries. Subsequently, these single cell samples were joined to form pools of 100 individual cells and analyzed using the ProteinChip technology; SELDI: surface-enhanced laser desorption and ionization. As a result, numerous protein signals that were differentially expressed in the three epidermal cell types could be detected. One of these proteins was characterized by tryptical digestion and subsequent identification via tandem quadrupole-time of flight (Q-TOF) mass spectrometry. Down regulation of this sequenced small subunit precursor of ribulose-1,5 bisphosphate carboxylase(C) oxygenase(O) (RuBisCo) in trichome and basal cells indicates the sink status of these cell types that are located on the surface of A. thaliana source leaves. Based on the obtained protein profiles, we suggest a close functional relationship between basal and trichome cells at the protein level.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jplph.2008.01.006DOI Listing
August 2008

Gene expression profiling of the different stages of Arabidopsis thaliana trichome development on the single cell level.

Plant Physiol Biochem 2008 Feb 13;46(2):160-73. Epub 2007 Nov 13.

Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany.

Leaf hairs (trichomes) of Arabidopsis thaliana are a model system for studying cell development, differentiation and cell cycle regulation. To exploit this model system with ultimate spatial resolution we applied single cell sampling, thus avoiding the averaging effect induced by complex tissue mixtures. In particular, we analysed gene expression profiles of two selected stages of the developing trichome: trichome initial cells and mature trichomes, as well as pavement cells. Ten single cells per sample were collected by glass microcapillaries and used for the generation of radioactive probes for subsequent hybridization to nylon filters representing approximately 8000 genes of A. thaliana. Functional categorization of genes transcribed in trichome initials, mature trichomes and pavement cells demonstrated involvement of these surface cells in the stress response. In silico promoter analysis of genes preferentially expressed in trichome initials revealed enrichment in MYB-binding sites and presence of elements involved in hormonal, metal, sulphur response and cell cycle regulation. Three candidate genes preferentially expressed in trichome initials were selected for further analysis: At3g16980 (putative RNA polymerase II), At5g15230 (GASA4) and At4g27260 (GH3.5, WES1). Promoter:GUS studies confirmed expression of the putative RNA polymerase II and the gibberellin responsive GASA4 in trichome initials and partially in mature trichomes. Functional implication of the three selected candidates in trichome development and hence in cell cycle regulation in A. thaliana is discussed. We suggest that these genes are involved in differentiation and initiation of endocycling during trichome development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.plaphy.2007.11.001DOI Listing
February 2008

Gene expression profiling of single epidermal, basal and trichome cells of Arabidopsis thaliana.

J Plant Physiol 2008 Sep 14;165(14):1530-44. Epub 2007 Nov 14.

Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany.

Samples of single epidermal, basal and trichome cells were collected by glass microcapillaries from 7-week-old Arabidopsis thaliana leaves. Transcript amplification of these single-cell samples was performed by RT PCR. For gene expression profiling, we hybridized the amplified transcriptome of each individual cell type to nylon membranes spotted with 16,000 Arabidopsis expressed sequence tags (ESTs). Initial analysis of the array filter data enabled us to functionally categorize transcripts that were present in each individual cell type. In order to confirm the filter array data, we used RT PCR. Results of this RT PCR approach confirmed the presence of 12 selected candidate genes in agreement with array filter hybridization data. Further, transcripts involved in detoxification and sulfur metabolism could be identified in epidermal cell extracts. Together, the results of our study provide the localization of approximately 1000 expressed genes to either pavement, basal or trichome cells. To cluster transcripts with similar expression levels, we developed a novel mathematical algorithm. Based on the mean and standard deviation, ratios of expression levels of a transcript were defined for pairs of the three cell types. This numerical analysis enabled subdivision into 67 categories of genes differentially expressed in epidermal, basal and trichome cells. Transcripts in each category displayed similar ratios of expression levels in the three cell types. Examples of these clusters are presented and discussed in Appendix A.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jplph.2007.06.017DOI Listing
September 2008

Deficiency of mitochondrial fumarase activity in tomato plants impairs photosynthesis via an effect on stomatal function.

Plant J 2007 Jun 25;50(6):1093-106. Epub 2007 Apr 25.

Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany.

Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of a fumarate hydratase (fumarase) gene in the antisense orientation and exhibiting considerable reductions in the mitochondrial activity of this enzyme show impaired photosynthesis. The rate of the tricarboxylic acid cycle was reduced in the transformants relative to the other major pathways of carbohydrate oxidation and the plants were characterized by a restricted rate of dark respiration. However, biochemical analyses revealed relatively little alteration in leaf metabolism as a consequence of reducing the fumarase activity. That said, in comparison to wild-type plants, CO(2) assimilation was reduced by up to 50% under atmospheric conditions and plants were characterized by a reduced biomass on a whole plant basis. Analysis of further photosynthetic parameters revealed that there was little difference in pigment content in the transformants but that the rate of transpiration and stomatal conductance was markedly reduced. Analysis of the response of the rate of photosynthesis to variation in the concentration of CO(2) confirmed that this restriction was due to a deficiency in stomatal function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-313X.2007.03115.xDOI Listing
June 2007
-->