Regina Feil

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

Are you Regina Feil?

Claim your profile

Publications (57)280.75 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Water availability is the biggest single limitation on plant productivity worldwide. In Arabidopsis, changes in metabolism and gene expression drive increased drought tolerance and initiate diverse drought avoidance and escape responses. To address regulatory processes that link these responses together, we set out to identify novel genes that govern early responses to drought. To do this, a high-resolution time series transcriptomics dataset was produced, coupled with detailed physiological and metabolic analyses of plants subjected to a slow transition from well-watered to drought conditions. 1815 drought-responsive differentially expressed genes were identified. The major early changes in gene expression coincided with a drop in carbon assimilation, and only in the late stages with an increase in foliar abscisic acid content. In order to identify gene regulatory networks (GRNs) mediating the transition between the early and late stages of drought, we used Bayesian network modelling of differentially expressed transcription factor (TF) genes. This approach identified AGAMOUS-LIKE22 as key hub gene in a TF GRN. It has previously been shown that AGL22 is involved in the transition from vegetative state to flowering but here we show that AGL22 expression influences steady state photosynthetic rates and lifetime water use. This suggests that AGL22 uniquely regulates a transcriptional network during drought stress, linking changes in primary metabolism and the initiation of stress responses.
    No preview · Article · Feb 2016 · The Plant Cell
  • Source

    Full-text · Dataset · Feb 2016
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Trehalose 6-phosphate (Tre6P) is an essential signal metabolite in plants, linking growth and development to carbon metabolism. The sucrose-Tre6P nexus model postulates that Tre6P acts as both a signal and negative feedback regulator of sucrose levels. To test this model, short-term metabolic responses to induced increases in Tre6P levels were investigated in Arabidopsis thaliana plants expressing the Escherichia coli Tre6P synthase (otsA) under the control of an ethanol-inducible promoter. Increased Tre6P led to a transient drop in sucrose content, post-translational activation of nitrate reductase and phosphoenolpyruvate carboxylase, and increased levels of organic and amino acids. Radio- ((14) CO2 ) and stable-isotope ((13) CO2 ) labelling experiments showed no change in the rates of photoassimilate export in plants with elevated Tre6P, but increased labelling of organic acids. It is concluded that high Tre6P lowers sucrose levels by stimulating nitrate assimilation and anaplerotic synthesis of organic acids, thereby diverting photoassimilates away from sucrose to generate carbon skeletons and fixed nitrogen for amino acid synthesis. These results are consistent with the sucrose-Tre6P nexus model and implicate Tre6P in coordinating carbon and nitrogen metabolism in plants. This article is protected by copyright. All rights reserved.
    Full-text · Article · Dec 2015 · The Plant Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: Plants respond to low carbon supply by massive reprogramming of the transcriptome and metabolome. We demonstrate here that the carbon starvation-induced NAC transcription factor ATAF1 from Arabidopsis thaliana plays an important role in this physiological process. We identified TREHALASE1 (TRE1), the only trehalase-encoding gene in Arabidopsis, as a direct downstream target of ATAF1. Overexpression of ATAF1 activates TRE1 expression and leads to reduced trehalose-6-phosphate levels and a sugar starvation metabolome. In accordance with changes in expression of starch biosynthesis and breakdown related genes, starch levels are generally reduced in ATAF1 overexpressors, but elevated in ataf1 knockout plants. At the global transcriptome level, genes affected by ATAF1 are broadly associated with energy and carbon starvation responses. Furthermore, transcriptional responses triggered by ATAF1 largely overlap with expression patterns observed in plants starved for carbon or energy supply. Collectively, our data highlight the existence of a positively acting feed-forward loop between ATAF1 expression, which is induced by carbon starvation, and the depletion of cellular carbon/energy pools that is triggered by the transcriptional regulation of downstream gene regulatory networks by ATAF1. Copyright © 2015, Plant Physiology.
    No preview · Article · Jul 2015 · Plant physiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Xanthomonas citri subsp. citri (Xcc) is a bacterial pathogen that causes citrus canker in susceptible Citrus spp. The Xcc genome contains genes encoding enzymes from three separate pathways of trehalose biosynthesis. Expression of genes encoding trehalose-6-phosphate synthase (otsA) and trehalose phosphatase (otsB) was highly induced during canker development, suggesting that the two-step pathway of trehalose biosynthesis via trehalose-6-phosphate has a function in pathogenesis. This pathway was eliminated from the bacterium by deletion of the otsA gene. The resulting XccΔotsA mutant produced less trehalose than the wild-type strain, was less resistant to salt and oxidative stresses, and was less able to colonize plant tissues. Gene expression and proteomic analyses of infected leaves showed that infection with XccΔotsA triggered only weak defence responses in the plant compared with infection with Xcc, and had less impact on the host plant's metabolism than the wild-type strain. These results suggested that trehalose of bacterial origin, synthesized via the otsA-otsB pathway, in Xcc, plays a role in modifying the host plant's metabolism to its own advantage but is also perceived by the plant as a sign of pathogen attack. Thus, trehalose biosynthesis has both positive and negative consequences for Xcc. On the one hand, it enables this bacterial pathogen to survive in the inhospitable environment of the leaf surface before infection and exploit the host plant's resources after infection, but on the other hand, it is a tell-tale sign of the pathogen's presence that triggers the plant to defend itself against infection. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.
    Full-text · Article · Mar 2015 · Journal of Experimental Botany
  • [Show abstract] [Hide abstract]
    ABSTRACT: Trehalose metabolism is essential for normal growth and development in higher plants. It is synthesized in a two-step pathway catalyzed by trehalose-6-phosphate (Tre6P) synthase (TPS) and trehalose phosphatase. Arabidopsis thaliana has 11 TPS or TPS-like proteins, which belong to two distinct clades: class I (AtTPS1-AtTPS4) and class II (AtTPS5-AtTPS11). Only AtTPS1 has previously been shown to have TPS activity. Null A. thaliana tps1 mutants fail to complete embryogenesis and rescued lines have stunted growth and delayed flowering, indicating that AtTPS1 is important throughout the life cycle. Here we show that expression of AtTPS2 or AtTPS4 enables the yeast tps1∆ tps2∆ mutant to grow on glucose and accumulate Tre6P and trehalose. Class II TPS genes did not complement the yeast mutant. Thus, A. thaliana has at least three catalytically active TPS isoforms, suggesting that loss of Tre6P production might not be the only reason for the growth defects of A. thaliana tps1 mutants.
    No preview · Article · Dec 2014 · Biochemical Journal
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mature leaves of plants transferred from low to high light typically increase their photosynthetic capacity. In Arabidopsis thaliana, this dynamic acclimation requires expression of GPT2, a glucose 6-phosphate/phosphate translocator. Here, we examine the impact of GPT2 on leaf metabolism and photosynthesis. Plants of wild-type and of a GPT2 knockout (gpt2.2) grown under low light achieved the same photosynthetic rate, despite having different metabolic and transcriptomic strategies. Immediately upon transfer to high light, gpt2.2 plants showed a higher rate of photosynthesis than wild-type (35%) however, over subsequent days, wild-type plants acclimated photosynthetic capacity, increasing photosynthesis 100 after 7 days. Wild-type plants accumulated more starch than gpt2.2 plants throughout acclimation. We suggest that GPT2 activity results in the net import of glucose 6-phosphate from cytosol to chloroplast, increasing starch synthesis. There was clear acclimation of metabolism, with short terms changes typically being reversed as plants acclimated. Distinct responses to light were seen in wild-type and gpt2.2 leaves. Significantly higher levels of sugar-phosphates were seen in gpt2.2. We suggest that GPT2 alters the distribution of metabolites between compartments and that this plays an essential role in allowing the cell to interpret environmental signals. This article is protected by copyright. All rights reserved.
    No preview · Article · Dec 2014 · Plant Cell and Environment
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arabidopsis (Arabidopsis thaliana) leaves synthesize starch faster in short days than in long days, but the mechanism that adjusts the rate of starch synthesis to daylength is unknown. To understand this mechanism, we first investigated whether adjustment occurs in mutants lacking components of the circadian clock or clock output pathways. Most mutants adjusted starch synthesis to daylength, but adjustment was compromised in plants lacking the GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F BOX1 components of the photoperiod-signaling pathway involved in flowering. We then examined whether the properties of the starch synthesis enzyme adenosine 59-diphosphate-glucose pyrophosphorylase (AGPase) are important for adjustment of starch synthesis to daylength. Modulation of AGPase activity is known to bring about short-term adjustments of photosynthate partitioning between starch and sucrose (Suc) synthesis. We found that adjustment of starch synthesis to daylength was compromised in plants expressing a deregulated bacterial AGPase in place of the endogenous AGPase and in plants containing mutant forms of the endogenous AGPase with altered allosteric regulatory properties. We suggest that the rate of starch synthesis is in part determined by growth rate at the end of the preceding night. If growth at night is low, as in short days, there is a delay before growth recovers during the next day, leading to accumulation of Suc and stimulation of starch synthesis via activation of AGPase. If growth at night is fast, photosynthate is used for growth at the start of the day, Suc does not accumulate, and starch synthesis is not up-regulated. © 2014 American Society of Plant Biologists. All rights reserved.
    Full-text · Article · Oct 2014 · Plant physiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Energy resources in plants are managed in continuously changing environments, such as changes occurring during the day/night cycle. Shading is an environmental disruption that decreases photosynthesis, compromises energy status, and impacts on crop productivity. The trehalose pathway plays a central but not well-defined role in maintaining energy balance. Here, we characterized the maize trehalose pathway genes and deciphered the impacts of the diurnal cycle and disruption of the day/night cycle on trehalose pathway gene expression and sugar metabolism. The maize genome encodes 14 trehalose-6-phosphate synthase (TPS) genes, 11 trehalose-6-phosphate phosphatase (TPP) genes, and one trehalase gene. Transcript abundance of most of these genes was impacted by the day/night cycle and extended dark stress, as were sucrose, hexose sugars, starch, and trehalose-6-phosphate (T6P) levels. After extended darkness, T6P levels inversely followed class II TPS and sucrose non-fermenting-related protein kinase 1 (SnRK1) target gene expression. Most significantly, T6P no longer tracked sucrose levels after extended darkness. These results showed: (i) conservation of the trehalose pathway in maize; (ii) that sucrose, hexose, starch, T6P, and TPS/TPP transcripts respond to the diurnal cycle; and(iii) that extended darkness disrupts the correlation between T6P and sucrose/hexose pools and affects SnRK1 target gene expression. A model for the role of the trehalose pathway in sensing of sucrose and energy status in maize seedlings is proposed.
    Full-text · Article · Sep 2014 · Journal of Experimental Botany
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The major component of starch is the branched glucan amylopectin. Structural features of amylopectin - the branching pattern and the chain length distribution - are thought to be key factors that enable it to form semi-crystalline starch granules. We varied both structural parameters by creating Arabidopsis mutants lacking combinations of starch synthases 1, 2 and 3 (to vary chain lengths) and the isoamylase 1 debranching enzyme (isa; to alter branching pattern). The isa mutant accumulates primarily phytoglycogen in leaf mesophyll cells, with only small amounts of starch in other cell types (epidermis and bundle sheath cells). This balance can be significantly shifted by mutating different starch synthases. Mutation of SS1 promoted starch synthesis, restoring granules in mesophyll cell plastids. Mutation of SS2 decreased starch synthesis, abolishing granules in epidermal and bundle sheath cells. Thus, the types of starch synthases present affect the crystallinity - and thus solubility - of the glucans made, compensating for or compounding the effects of an aberrant branching pattern. Interestingly, ss2 mutant plants contained small amounts of phytoglycogen in addition to aberrant starch. Likewise, ss2ss3 plants contained phytoglycogen, but were almost devoid of glucan despite retaining other SS isoforms. Surprisingly, in the ss2ss3isa triple mutants, glucan production was restored, indicating that in ss2ss3, starch synthase activity per se is not limiting but that the isoamylase suppresses glucan accumulation. We conclude that loss of only starch synthases can cause phytoglycogen production. This readily degraded by isoamylase and other enzymes so does not accumulate and was previously unnoticed.
    Preview · Article · Jun 2014 · Plant physiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Non-aqueous fractionation is a technique for enrichment of different subcellular compartments derived from lyophilised material. It was developed to study the subcellular distribution of metabolites. Here we analyse the distribution of about 1000 proteins and 70 metabolites, including 22 phosphorylated intermediates in wild-type Arabidopsis rosette leaves, using non-aqueous gradients divided into 12 fractions. Good separation of plastidial, cytosolic and vacuolar metabolites and proteins was achieved but cytosolic, mitochondrial and peroxisomal proteins clustered together. There was considerable heterogeneity in the fractional distribution of transcription factors, ribosomal proteins and subunits of the vacuolar-ATPase, indicating diverse compartmental location. Within the plastid, sub-organellar separation of thylakoids and stromal proteins was observed. Metabolites from the Calvin-Benson cycle, photorespiration, starch and sucrose synthesis, glycolysis and tricarboxylic acid cycle grouped with their associated proteins of the respective compartment. Non-aqueous fractionation thus proved a powerful method for the study of the organellar, and in some cases sub-organellar, distribution of proteins and their association with metabolites. It remains the technique of choice for assignment of subcellular location to metabolites in intact plant tissues and thus the technique of choice for doing combined metabolite-protein analysis in the same tissue sample.
    Full-text · Article · May 2014 · Molecular & Cellular Proteomics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, has a profound influence on plant metabolism, growth, and development. It has been proposed that Tre6P acts as a signal of sugar availability and is possibly specific for sucrose status. Short-term sugar-feeding experiments were carried out with carbon-starved Arabidopsis thaliana seedlings grown in axenic shaking liquid cultures. Tre6P increased when seedlings were exogenously supplied with sucrose, or with hexoses that can be metabolized to sucrose, such as glucose and fructose. Conditional correlation analysis and inhibitor experiments indicated that the hexose-induced increase in Tre6P was an indirect response dependent on conversion of the hexose sugars to sucrose. Tre6P content was affected by changes in nitrogen status, but this response was also attributable to parallel changes in sucrose. The sucrose-induced rise in Tre6P was unaffected by cordycepin but almost completely blocked by cycloheximide, indicating that de novo protein synthesis is necessary for the response. There was a strong correlation between Tre6P and sucrose even in lines that constitutively express heterologous trehalose-phosphate synthase or trehalose-phosphate phosphatase, although the Tre6P:sucrose ratio was shifted higher or lower, respectively. It is proposed that the Tre6P:sucrose ratio is a critical parameter for the plant and forms part of a homeostatic mechanism to maintain sucrose levels within a range that is appropriate for the cell type and developmental stage of the plant.
    Full-text · Article · Jan 2014 · Journal of Experimental Botany
  • [Show abstract] [Hide abstract]
    ABSTRACT: In short photoperiods plants accumulate starch more rapidly in the light and degrade it more slowly at night, ensuring that their starch reserves last until dawn. To investigate the accompanying changes in the timing of growth, Arabidopsis was grown in a range of photoperiods and analysed for rosette biomass, photosynthesis, respiration, ribosome abundance, polysome loading, starch, and over 40 metabolites at dawn and dusk. The dataset was used to model growth rates in the daytime and night, and to identify metabolites that correlate with growth. Modelled growth rates and polysome loading were high in the daytime and at night in long photoperiods, but decreased at night in short photoperiods. Ribosome abundance was similar in all photoperiods. It is discussed how the amount of starch accumulated in the light period, the length of the night and maintenance costs interact to constrain growth at night in short photoperiods, and alter the strategy for optimising ribosome use. Significant correlations were found in the daytime and the night between growth rates and the levels of the sugar-signal trehalose 6-phosphate and the amino acid biosynthesis intermediate shikimate, identifying these metabolites as hubs in a network that coordinates growth with diurnal changes in the carbon supply.
    No preview · Article · Oct 2013 · Molecular Plant
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Many plants accumulate substantial starch reserves in their leaves during the day, and remobilise them at night to provide carbon and energy for maintenance and growth. In this paper we explore the role of a sugar signalling metabolite, trehalose-6-phosphate (Tre6P), in regulating the accumulation and turnover of transitory starch in Arabidopsis leaves. Ethanol-induced overexpression of trehalose-phosphate synthase (TPS) during the day increased Tre6P levels up to 11-fold. There was a transient increase in the rate of starch accumulation in the middle of the day, but this was not linked to reductive activation of ADP-glucose pyrophosphorylase. A 2 to 3-fold increase in Tre6P during the night led to significant inhibition of starch degradation. Maltose and maltotriose did not accumulate, suggesting that Tre6P affects an early step in the pathway of starch degradation in the chloroplasts. Starch granules isolated from induced plants had a higher Pi content than granules from non-induced control plants, consistent with either disruption of the phosphorylation-dephosphorylation cycle that is essential for efficient starch breakdown, or with inhibition of starch hydrolysis by β-amylase. Non-aqueous fractionation of leaves showed that Tre6P is predominantly located in the cytosol, with estimated in vivo Tre6P concentrations of 4-7 µM in the cytosol, 0.2-0.5 µM in the chloroplasts and 0.05 µM in the vacuole. It is proposed that Tre6P is a component in a signalling pathway that mediates feedback regulation of starch breakdown by sucrose, potentially linking starch turnover to demand for sucrose by growing sink organs at night.
    Full-text · Article · Sep 2013 · Plant physiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arabidopsis thaliana mutants lacking the SS4 isoform of starch synthase have strongly reduced numbers of starch granules per chloroplast, suggesting that SS4 is necessary for the normal generation of starch granules. To establish whether it plays a direct role in this process, we investigated the circumstances in which granules are formed in ss4 mutants. Starch granule numbers and distribution and the accumulation of starch synthase substrates and products were investigated during ss4 leaf development, and in ss4 mutants carrying mutations or transgenes that affect starch turnover or chloroplast volume. We found that immature ss4 leaves have no starch granules, but accumulate high concentrations of the starch synthase substrate ADPglucose. Granule numbers are partially restored by elevating the capacity for glucan synthesis (via expression of bacterial glycogen synthase) or by increasing the volumes of individual chloroplasts (via introduction of arc mutations). However, these granules are abnormal in distribution, size and shape. SS4 is an essential component of a mechanism that coordinates granule formation with chloroplast division during leaf expansion and determines the abundance and the flattened, discoid shape of leaf starch granules.
    Preview · Article · Aug 2013 · New Phytologist
  • [Show abstract] [Hide abstract]
    ABSTRACT: Starch synthase 4 (SS4) is required for proper starch granule initiation in Arabidopsis thaliana, although starch synthase 3 (SS3) can partially replace its function. Unlike other starch deficient mutants, ss4 and ss3/ss4 mutants grow poorly even under long-day conditions. They have less chlorophyll and carotenoids than wild type (WT) and lower maximal rates of photosynthesis. There is evidence of photo-oxidative damage of the photosynthetic apparatus in the mutants from chlorophyll a fluorescence parameters and their high levels of malondialdehyde. Metabolite profiling revealed that ss3/ss4 accumulates over 170 times more ADP-glucose than WT plants. Restricting ADP-glucose synthesis, by introducing mutations in the plastidial phosphoglucomutase (pgm1) or the small subunit of ADP-glucose pyrophosphorylase (aps1), largely restored photosynthetic capacity and growth in pgm1/ss3/ss4 and aps1/ss3/ss4 triple mutants. It is proposed that the accumulation of ADP-glucose in the ss3/ss4 mutant sequesters a large part of the plastidial pools of adenine nucleotides, which limits photophosphorylation leading to photo-oxidative stress, causing the chlorotic and stunted growth phenotypes of the plants.
    No preview · Article · Jul 2013 · Plant physiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Full text URL: http://www.plantmethods.com/content/9/1/21 Trehalose is a non-reducing disaccharide that is used as an osmolyte, transport sugar, carbon reserve and stress protectant in a wide range of organisms. In plants, trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, is thought to be a signal of sucrose status. Trehalose itself may play a role in pathogenic and symbiotic plant-microbe interactions, in responses to abiotic stress and in developmental signalling, but its precise functions are unknown. A major obstacle to investigating its function is the technical difficulty of measuring the very low levels of trehalose usually found in plant tissues, as most of the established trehalose assays lack sufficient specificity and/or sensitivity. A kinetic assay for trehalose was established using recombinant Escherichia coli cytoplasmic trehalase (treF), which was shown to be highly specific for trehalose. Hydrolysis of trehalose to glucose is monitored fluorometrically and the trehalose content of the tissue extract is determined from an internal calibration curve. The assay is linear for 0.2-40 pmol trehalose, and recoveries of trehalose were >=88%. A. thaliana Col-0 rosettes contain about 20--30 nmol g-1FW of trehalose, increasing to about 50--60 nmol g-1FW in plants grown at 8[degree sign]C. Trehalose is not correlated with sucrose content, whereas a strong correlation between Tre6P and sucrose was confirmed. The trehalose contents of ear inflorescence primordia from the maize ramosa3 mutant and wild type plants were 6.6+/-2.6 nmol g-1FW and 19.0+/-12.7 nmol g-1FW, respectively. The trehalose:Tre6P ratios in the ramosa3 and wild-type primordia were 2.43+/-0.85 and 6.16+/-3.45, respectively. The fluorometric assay is highly specific for trehalose and sensitive enough to measure the trehalose content of very small amounts of plant tissue. Chilling induced a 2-fold accumulation of trehalose in A. thaliana rosettes, but the levels were too low to make a substantial quantitative contribution to osmoregulation. Trehalose is unlikely to function as a signal of sucrose status. The abnormal inflorescence branching phenotype of the maize ramosa3 mutant might be linked to a decrease in trehalose levels in the inflorescence primordia or a downward shift in the trehalose:Tre6P ratio.
    Full-text · Article · Jun 2013 · Plant Methods
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Photosynthesis is the basis for life, and its optimization is a key biotechnological aim given the problems of population explosion and environmental deterioration. We describe a method to resolve intracellular fluxes in intact Arabidopsis thaliana rosettes based on time-dependent labeling patterns in the metabolome. Plants photosynthesizing under limiting irradiance and ambient CO(2) in a custom-built chamber were transferred into a (13)CO(2)-enriched environment. The isotope labeling patterns of 40 metabolites were obtained using liquid or gas chromatography coupled to mass spectrometry. Labeling kinetics revealed striking differences between metabolites. At a qualitative level, they matched expectations in terms of pathway topology and stoichiometry, but some unexpected features point to the complexity of subcellular and cellular compartmentation. To achieve quantitative insights, the data set was used for estimating fluxes in the framework of kinetic flux profiling. We benchmarked flux estimates to four classically determined flux signatures of photosynthesis and assessed the robustness of the estimates with respect to different features of the underlying metabolic model and the time-resolved data set.
    Full-text · Article · Feb 2013 · The Plant Cell
  • [Show abstract] [Hide abstract]
    ABSTRACT: The timing of the induction of flowering determines to a large extent the reproductive success of plants. Plants integrate diverse environmental and endogenous signals to ensure the timely transition from vegetative growth to flowering. Carbohydrates are thought to play a crucial role in the regulation of flowering, and trehalose-6-phosphate (T6P) has been suggested to function as a proxy for carbohydrate status in plants. The loss of TREHALOSE-6-PHOSPHATE SYNTHASE 1 (TPS1) causes Arabidopsis thaliana to flower extremely late, even under otherwise inductive environmental conditions. This suggests that TPS1 is required for the timely initiation of flowering. We show that the T6P pathway affects flowering both in the leaves and at the shoot meristem, and integrate TPS1 into the existing genetic framework of flowering-time control.
    No preview · Article · Feb 2013 · Science
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Changes in carbohydrate metabolism during grape berry development play a central role in shaping the final composition of the fruit. The present work aimed to identify metabolic switches during grape development and to provide insights into the timing of developmental regulation of carbohydrate metabolism. Metabolites from central carbon metabolism were measured using high-pressure anion-exchange chromatography coupled to tandem mass spectrometry and enzymatic assays during the development of grape berries from either field-grown vines or fruiting cuttings grown in the greenhouse. Principal component analysis readily discriminated the various stages of berry development, with similar trajectories for field-grown and greenhouse samples. This showed that each stage of fruit development had a characteristic metabolic profile and provided compelling evidence that the fruit-bearing cuttings are a useful model system to investigate regulation of central carbon metabolism in grape berry. The metabolites measured showed tight coordination within their respective pathways, clustering into sugars and sugar-phosphate metabolism, glycolysis, and the tricarboxylic acid cycle. In addition, there was a pronounced shift in metabolism around veraison, characterized by rapidly increasing sugar levels and decreasing organic acids. In contrast, glycolytic intermediates and sugar phosphates declined before veraison but remained fairly stable post-veraison. In summary, these detailed and comprehensive metabolite analyses revealed the timing of important switches in primary carbohydrate metabolism, which could be related to transcriptional and developmental changes within the berry to achieve an integrated understanding of grape berry development. The results are discussed in a meta-analysis comparing metabolic changes in climacteric versus non-climacteric fleshy fruits.
    Full-text · Article · Jan 2013 · Journal of Experimental Botany