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Metabolomics plays a pivotal role in systems biology, and NMR is a central tool with high precision and exceptional resolution of chemical information. Most NMR metabolomic studies are based on 1H 1D spectroscopy, severely limited by peak overlap. 13C NMR benefits from a larger signal dispersion but is barely used in metabolomics due to ca. 6000-fold lower sensitivity. We introduce a new approach, based on hyperpolarized 13C NMR at natural abundance, that circumvents this limitation. A new untargeted NMR-based metabolomic workflow based on dissolution dynamic nuclear polarization (d-DNP) for the first time enabled hyperpolarized natural abundance 13C metabolomics. Statistical analysis of resulting hyperpolarized 13C data distinguishes two groups of plant (tomato) extracts and highlights biomarkers, in full agreement with previous results on the same biological model. We also optimize parameters of the semiautomated d-DNP system suitable for high-throughput studies.

This article describes how metabolomic data were produced on sunflower plants subjected to water deficit. Twenty-four sunflower (Helianthus annuusL.) genotypes were selected to represent genetic diversity within cultivated sunflower and included both inbred lines and their hybrids. Drought stress was applied at the vegetative stage to plants cultivated in pots using the high-throughput phenotyping facility Heliaphen. Here, we provide untargeted and targeted metabolomic data of sunflower leaves. These compositional data differentiate both plant water status and different genotype groups. They constitute a valuable resource for the community to study the adaptation of crops to drought and the metabolic bases of heterosis.

Abstract: The goal of the present study was to identify candidate genes (CGs) involved in fruit quality in peach that can be transferred to other Rosaceae species. Two cDNA libraries from fruit of the “Fantasia” peach cultivar, constructed at two stages of development, were used to generate a set of expressed sequence tag sequences. A total of 1,730 peach unigenes were obtained after clustering. Sequences and corresponding annotations were stored in a relational database and are available through a web interface. Fifty-nine CGs involved in fruit growth and development or fruit quality at maturity, focusing on sweetness, acidity, and phenolic compound content, were selected according to their annotation. Fifty-five primer pairs, designed from peach CG sequences and giving PCR products in peach, were tested in strawberry and 36 gave amplified products. Eight CGs were mapped in peach, 14 in strawberry, four in both species and confirmed the pattern of synteny already proposed using comparative mapping. In peach, the CGs are located in three linkage groups (3, 5, 7), and in strawberry they are distributed in all seven Fragaria linkage groups. Colocalization between some of these CGs and quantitative trait loci for fruit quality traits were identified and are awaiting confirmation in further analyses.

Abstract: Tomato is an essential crop in terms of economic importance and nutritional quality. In France, the third most important region for tomato (Solanum lycopersicum L.) production is Aquitaine where the major part of production is now grown soilless under greenhouse conditions with harvest from March to November. Tomato fruit quality at harvest is a direct function of its metabolite content at that time. The aim of this work was to use a global approach to characterize changes in the fruit organoleptic quality at harvest under commercial culture conditions during an entire season for two varieties and two different fertilization practices (with or without recycling of the nutrient solution) for one variety. Absolute quantification data of 32 major compounds in fruit without seeds were obtained through untargeted (proton nuclear magnetic resonance, 1H-NMR) quantitative profiling. These data were complemented by colorimetric analysis of ascorbate and total phenolics. They were analyzed with chemometric approaches. Principal component analysis (PCA) or partial least square analyses (PLS) revealed more discriminant metabolites for season than for variety and showed that nutrient solution recycling had very little effect on fruit composition. These tendencies were confirmed with univariate analyses. 1H-NMR profiling complemented with colorimetric analyses therefore provided a diagnostic tool to follow the changes in organoleptic and nutritional quality of tomato. In addition the quantitative information generated will help to increase our knowledge on the mechanisms of plant response to environmental modifications.

Abstract: Tomato, an essential crop in terms of economic importance and nutritional quality, is also used as a model species for all fleshy fruits and for genomics of Solanaceae. Tomato fruit quality at harvest is a direct function of its metabolite content, which in turn is a result of many physiological changes during fruit development. The aim of the work reported here was to develop a global approach to characterize changes in metabolic profiles in two interdependent tissues from the same tomato fruits. Absolute quantification data of compounds in flesh and seeds from 8 days to 45 days post anthesis (DPA) were obtained through untargeted (proton nuclear magnetic resonance, 1H-NMR) and targeted metabolic profiling (liquid chromatography with diode array detection (LC-DAD) or gas chromatography with flame ionization detection (GC-FID)). These data were analyzed with chemometric approaches. Kohonen self organizing maps (SOM) analysis of these data allowed us to combine multivariate (distribution of samples on Kohonen SOMs) and univariate information (component plane representation of metabolites) in a single analysis. This strategy confirmed published data and brought new insights on tomato flesh and seed composition, thus demonstrating its potential in metabolomics. The compositional changes were related to physiological processes occurring in each tissue. They pointed to (i) some parallel changes at early stages in relation to cell division and transitory storage of carbon, (ii) metabolites participating in the fleshy trait and (iii) metabolites involved in the specific developmental patterns of the seeds.

Rain-induced fruit cracking is a limiting factor for sweet cherry (Prunus avium L.) growers in many production areas. Although many studies have concerned this complex phenomenon, the basic mechanisms involved in fruit cracking remain unclear. We re-examined the relations between osmotic potential and cracking susceptibility in cherry fruit by comparing the osmotic contribution of the major metabolites separately in flesh and skin, in four cultivars (with different levels of susceptibility to cracking) at four stages of development. Several differences were observed between flesh and skin revealing compositional gradients in the fruit tissues. Acidity and malate concentrations were higher in flesh than in skin for all stages. The absolute value of osmotic potential was higher but the contribution of the sum of sugars to osmotic potential was lower in flesh than in skin. As determined using fruit immersion test, ‘Fermina’ and ‘Regina’ were less susceptible to fruit cracking than ‘Lapins’ and ‘Brooks’. At commercial maturity when fruit susceptibility to cracking was highest, no clear difference appeared between ‘Brooks’ and ‘Lapins’ compared to ‘Regina’ and ‘Fermina’ for flesh or skin osmolarity and for the contribution of the major sugars or organic acids to skin and flesh osmotic potential. [ABSTRACT FROM AUTHOR]

Metabolic profiling by 1-dimensional (1-D) 1H-nuclear magnetic resonance (NMR) was tested for absolute quantification of soluble sugars, organic acids, amino acids and some secondary metabolites in fruit, roots and leaves. The metabolite responsible for each peak of the 1H-NMR spectra was identified from spectra of pure compounds. Peak identity was confirmed by the addition of a small amount of commercially-available pure substance. 1H-NMR spectra acquisition was automated. 1H-NMR absolute quantification was performed with a synthesised electronic reference signal and validated by comparison with enzymatic or HPLC analyses; the correlation coefficients between 1H-NMR data and enzymatic or HPLC data were highly significant. Depending on the species and tissues, 14?17 metabolites could be quantified with 15?25 min acquisition time. The detection limit was approximately 1?9 g in the NMR tube, depending on the compound. Quantitative data were used for (1) a genetic study of strawberry fruit quality, (2) a functional study of tomato transformants overexpressing hexokinase and (3) a study of Arabidopsis phosphoenolpyruvate carboxylase transformants with several lines showing decreased activity of the enzyme. Biochemical phenotyping of the fruits of a strawberry offspring allowed the detection of quantitative trait loci (QTL) controlling fruit quality. Comparison of the roots of wild types and hexokinase tomato transformants using principal component analysis of metabolic profiles revealed that environmental factors, i.e. culture conditions, can significantly modify the metabolic status of plants and thus hide or emphasise the expression of a given genetic background. The decrease in phosphoenolpyruvate carboxylase activity (up to 75%) in Arabidopsis transformants impacted on the metabolic profiles without compromising plant growth, thus supporting the idea that the enzyme has a low influence on the carbon flux through the anaplerotic pathway.

Abstract. The protein level and regulation of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31, involved in malic acid synthesis) was studied during the fruit development of two grape (Vitis vinifera L.) varieties, ‘Cabernet Sauvignon’ and ‘Gora Chirine’, with berries of normal and low organic acid content, respectively. The protein level and in vitro activity were higher in the low-acid variety than in the normal-acid variety for most stages. In vivo PEPC activity, measured using 14 CO2 labelling, was significantly higher in the low-acid variety than in the normal-acid variety about 1 week before and 1 week after veraison (the day which corresponds to the onset of ripening). However, partitioning into malate was the same for both varieties. Antibodies raised against the N-terminal part of SorghumPEPC recognised the grape berry PEPC, indicating the presence of the consensus phosphorylation site involved in PEPC regulation. PEPC phosphorylation status was estimated by studying sensitivity to pH and malate. Grape berry PEPC appeared more sensitive to low pH and malate during ripening (IC50 malate, 0.2–0.7 mM) compared to during the earlier stages of development (IC50 malate, 1.2–2 mM) for both varieties. Therefore, in the normal-acid variety, PEPC seems to participate in controlling malic acid accumulation but does not seem to control the differences in malic acid concentration observed between the two varieties. Keywords: Vitis vinifera, metabolism, regulation, 14 C labelling, organic acids, malate.

Changes in photosynthetic carbon partitioning were determined, during 14CO2 pulse-chase experiments, in fully-expanded leaves of olive (Olea europaea L. cv. Frantoio) plants treated in containers with 100 mM NaCl for 5 weeks and compared with partitioning in leaves of untreated plants. Salt stress caused an increase in the radioactivity partitioned into mannitol and a decrease of that recovered as glucose. The radioactivity in sucrose was significantly reduced in salt-treated plants after 19.5 min of chase. There was no difference between the two treatments in the radioactivity found in fructose and galactose, whereas a significant decrease in the radioactivity found in stachyose and raffinose of salt-treated leaves was observed after 19.5 min chase. The radioactivity incorporated into starch was 11 and 16% of the total in control and salt-treated leaves respectively. There were no significant differences in the leaf pools of soluble carbohydrates over the chase period, except for mannitol which increased in the leaf tissue of salt-treated plants. Over the course of the diurnal period, and under high irradiance conditions, the leaf mannitol content increased more markedly in salt-treated plants than in the controls. In contrast, contents of other nonstructural carbohydrates were not affected by the 100 mM NaCl treatment.