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1.
Plant Physiol ; 177(2): 565-593, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29686055

RESUMO

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 raptor1b mutations on growth and physiology in Arabidopsis (Arabidopsis thaliana) by detailed phenotyping, metabolomic, lipidomic, and proteomic analyses. Mutation of RAPTOR1B 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 (Oryza sativa), we found that the Arabidopsis raptor1b mutation did not affect chloroplast development or photosynthetic electron transport efficiency; however, it resulted in decreased CO2 assimilation rate and increased stomatal conductance. The raptor1b 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.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Ácido Abscísico/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Carbono/metabolismo , Dióxido de Carbono/metabolismo , Regulação da Expressão Gênica de Plantas , Lipídeos/química , Lipídeos/genética , Meristema/genética , Meristema/fisiologia , Mutação , Fixação de Nitrogênio/genética , Fotossíntese/fisiologia , Folhas de Planta/anatomia & histologia , Folhas de Planta/fisiologia , Folhas de Planta/ultraestrutura , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Espécies Reativas de Oxigênio/metabolismo , Metabolismo Secundário/genética
2.
Ann Bot ; 122(5): 735-739, 2018 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-29373629

RESUMO

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.


Assuntos
Ritmo Circadiano , Gravitação , Árvores/fisiologia , Lua
3.
Ann Bot ; 121(7): e1-e6, 2018 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-29373644

RESUMO

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.

4.
Ann Bot ; 122(5): 725-733, 2018 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-29236939

RESUMO

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.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Ritmo Circadiano , Gravitação , Raízes de Plantas/crescimento & desenvolvimento , Cinética , Lua
5.
Plant Cell ; 25(12): 4941-55, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24363315

RESUMO

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.


Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/fisiologia , Estresse Fisiológico , Fatores de Transcrição/fisiologia , Aminoácido Oxirredutases/genética , Aminoácido Oxirredutases/metabolismo , Aminoácido Oxirredutases/fisiologia , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sítios de Ligação , Crescimento Celular , Regulação da Expressão Gênica de Plantas , Mutagênese Insercional , Folhas de Planta/genética , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/fisiologia , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/fisiologia , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/fisiologia , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/fisiologia , Regiões Promotoras Genéticas , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Água
6.
Plant Cell ; 25(6): 2115-31, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23800963

RESUMO

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.


Assuntos
Oryza/metabolismo , Proteínas de Plantas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Cloreto de Sódio/farmacologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Técnicas de Silenciamento de Genes , Peróxido de Hidrogênio/farmacologia , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , MAP Quinase Quinase Quinases/genética , MAP Quinase Quinase Quinases/metabolismo , Microscopia Confocal , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Oryza/genética , Oryza/crescimento & desenvolvimento , Oxidantes/farmacologia , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Ligação Proteica , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Tolerância ao Sal/genética , Estresse Fisiológico/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
7.
Planta ; 241(6): 1509-18, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25795423

RESUMO

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.


Assuntos
Arabidopsis/fisiologia , Gravitação , Lua , Folhas de Planta/fisiologia , Voo Espacial , Ritmo Circadiano/efeitos da radiação , Europa (Continente) , Geografia , Cinética , Luz , Movimento , Folhas de Planta/efeitos da radiação
8.
Plant Physiol ; 165(2): 715-731, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24777345

RESUMO

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.

9.
Ann Bot ; 121(7): e7, 2018 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-29893882
10.
Ann Bot ; 111(5): 859-72, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23532042

RESUMO

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.


Assuntos
Arabidopsis/fisiologia , Campos Magnéticos , Lua , Raízes de Plantas/crescimento & desenvolvimento , Sistema Solar , Ondas de Maré , Arabidopsis/crescimento & desenvolvimento , Pressão Atmosférica , Gravitropismo , Periodicidade , Raízes de Plantas/fisiologia , Estações do Ano , Fatores de Tempo
11.
New Phytol ; 195(2): 346-355, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22583121

RESUMO

• 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.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/efeitos da radiação , Gravitação , Lua , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/efeitos da radiação , Sistema Solar , Ritmo Circadiano/efeitos da radiação , Cinética , Luz , Fotoperíodo , Plântula/crescimento & desenvolvimento , Plântula/efeitos da radiação
12.
Plant Physiol ; 157(4): 1650-63, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21972266

RESUMO

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.


Assuntos
Frutas/crescimento & desenvolvimento , Fotossíntese/fisiologia , Proteínas de Plantas/metabolismo , Sementes/crescimento & desenvolvimento , Solanum lycopersicum/crescimento & desenvolvimento , Ácido Aminolevulínico/metabolismo , Frutas/genética , Frutas/metabolismo , Frutas/fisiologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/fisiologia , Glucuronidase , Solanum lycopersicum/genética , Solanum lycopersicum/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Especificidade de Órgãos , Fenótipo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Reprodução , Sementes/genética , Sementes/metabolismo
13.
Ann Bot ; 110(2): 301-18, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22437666

RESUMO

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.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/efeitos da radiação , Gravitação , Gravitropismo/fisiologia , Fenômenos Fisiológicos Vegetais/efeitos da radiação , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/efeitos da radiação , Lua , Folhas de Planta/crescimento & desenvolvimento , Caules de Planta/crescimento & desenvolvimento , Sistema Solar , Ondas de Maré
14.
Plant Cell Environ ; 34(6): 877-894, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21332506

RESUMO

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.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Carbono/metabolismo , Ritmo Circadiano/fisiologia , Raízes de Plantas/crescimento & desenvolvimento , Arabidopsis/efeitos dos fármacos , Proteínas de Arabidopsis/metabolismo , Metabolismo dos Carboidratos/efeitos dos fármacos , Relógios Circadianos/efeitos dos fármacos , Ritmo Circadiano/efeitos dos fármacos , Escuridão , Cinética , Modelos Biológicos , Mutação/genética , Fotoperíodo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Amido/metabolismo , Sacarose/metabolismo , Sacarose/farmacologia
15.
Plant Cell Environ ; 33(11): 1974-88, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20573050

RESUMO

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.


Assuntos
Aclimatação/fisiologia , Arabidopsis/fisiologia , Luz , Fotossíntese , Enxofre/metabolismo , Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Clorofila/análise , Transporte de Elétrons , Estresse Fisiológico
16.
J Exp Bot ; 61(5): 1321-35, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20150518

RESUMO

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.


Assuntos
Arabidopsis/metabolismo , Arabidopsis/ultraestrutura , Cromatografia Gasosa-Espectrometria de Massas , Regulação da Expressão Gênica de Plantas/fisiologia , Metaboloma/fisiologia , Microscopia Eletrônica de Varredura
17.
Ann Bot ; 105(5): 783-91, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20421235

RESUMO

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.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Raízes de Plantas/crescimento & desenvolvimento , Algoritmos , Cinética
18.
Plant Physiol Biochem ; 46(2): 160-73, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18160300

RESUMO

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.


Assuntos
Arabidopsis/genética , Perfilação da Expressão Gênica/métodos , Epiderme Vegetal/genética , Folhas de Planta/genética , Arabidopsis/citologia , Biologia Computacional , Regulação da Expressão Gênica de Plantas , Epiderme Vegetal/citologia , Epiderme Vegetal/crescimento & desenvolvimento , Folhas de Planta/citologia , Regiões Promotoras Genéticas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa
19.
Plant Signal Behav ; 10(9): e1057367, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26376108

RESUMO

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).


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Lua , Sistema Solar , Movimentos da Água , Arabidopsis/efeitos da radiação , Fluorescência , Folhas de Planta/metabolismo , Teoria Quântica , Fatores de Tempo
20.
Phytochemistry ; 65(11): 1641-9, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15276459

RESUMO

Metabolite, protein, and transcript analysis at the cellular level gives unparalleled insight into the complex roles tissues play in the plant system. However, while capillary electrophoresis and PCR amplification strategies make the profiling of metabolites and transcripts in specific cell types possible, the profiling of proteins in small samples represents a bottleneck. Here for the first time protein profiling has been achieved in a specific plant cell type: The application of specific cell sampling and shotgun peptide sequencing (nano LC/MS/MS) resulted in the identification of 63 unique proteins from pooled Arabidopsis trichome cells. A complete S-adenosylmethionine pathway cluster, two S-adenosylmethionine synthase isoforms, a glutathione S-conjugate translocator and other proteins involved in sulfur metabolism and detoxification are shown to be present in these cells, in agreement with previous work done at the level of trichome transcript analysis. The technology described here brings the simultaneous identification and localization of physiologically relevant cellular proteins within reach.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Perfilação da Expressão Gênica , Espectrometria de Massas/métodos , Enxofre/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/análise , Proteínas de Arabidopsis/genética , Bases de Dados de Proteínas , Regulação da Expressão Gênica de Plantas , Modelos Biológicos , Epiderme Vegetal/citologia , Epiderme Vegetal/metabolismo
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