Changes in quinic acid metabolism during fruit development in three kiwifruit species

Mycorrhizal Symbiosis Can Change the Composition of Secondary Metabolites in Fruits of Solanum nigrum L

Solanum nigrum is a common weed in arable land, while being used in traditional medicine around the world due to its remarkable levels of valuable secondary metabolites. Agronomic and biological techniques can alter the production of a specific metabolite by influencing plant growth and metabolism. The effects of colonization with three arbuscular mycorrhizal fungi (AMF), including Funneliformis mosseae, Rhizoglomus intraradices, and Rhizoglomus fasciculatum, on the chemical composition of S. nigrum fruits were evaluated by gas chromatography-mass spectrometry (GC-MS) analysis. More than 100 different chemical constituents were evaluated by GC-MS. Our study revealed that the levels of phenols (quinic acid), benzenes (hydroquinone), sulfur-containing compounds, lactone and carboxylic acids were improved by R. intraradices. In contrast, hydroxymethylfurfural increased by 68 % in R. fasciculatum inoculated with uninoculated S. nigrum plants, and this species was also the most efficient in inducing sugar compounds (D-galactose, lactose, and melezitose). Our results suggest that AMF colonization is an effective biological strategy that can alter the chemical composition and improve the medicinal properties of S. nigrum.

Chitosan-based coating enriched with melezitose alters primary metabolites in fresh-cut pineapple during storage

Demand for minimally processed fresh fruit is increasing due to its convenience. However, the distribution of fresh-cut fruits is limited because of their short shelf life. Pineapple, a popular tropical fruit, sold in fresh-cut form has a shelf life of approximately 5-7 days at 4 °C. Chitosan, an edible coating, is commonly used to prolong the shelf life of food products. Similarly, the sugar melezitose has been reported to change during pineapple ripening and may play a role in regulating the shelf life of pineapple. However, the direct effects of this sugar have yet to be studied. The objective of this study was to investigate the effect of chitosan coating with melezitose to prolong the shelf life of fresh-cut pineapple. Full-ripe Bogor pineapples from Okinawa, Japan, were cut into cubes and soaked in either chitosan 1.25%, melezitose 5 mg/L, or chitosan+melezitose and stored for 5 days under dark conditions (23.6 ± 0.5 °C; relative humidity, 40.0 ± 10.4%). None of the treatments significantly altered the weight loss or color changes in the fresh-cut fruit. However, treatment significantly altered the primary metabolites, namely quinic acid, sucrose, and xylitol based on orthogonal projection to latent structures data with the screening from p-value score. Moreover, cell-wall metabolism is possibly affected in pineapple cut fruit treated by chitosan-melezitose as shown from metabolite sets enrichment analysis. This study showed that chitosan added with melezitose might have potential to prolong the shelf-life of fresh-cut pineapple, providing a basis for further post-harvest studies of the whole pineapple fruit.

Longitudinal Plant Health Monitoring via High-Resolution Mass Spectrometry Screening Workflows: Application to a Fertilizer Mediated Tomato Growth Experiment

Significant efforts have been spent in the modern era towards implementing environmentally friendly procedures like composting to mitigate the negative effects of intensive agricultural practices. In this context, a novel fertilizer was produced via the hydrolysis of an onion-derived compost, and has been previously comprehensively chemically characterized. In order to characterize its efficacy, the product was applied to tomato plants at five time points to monitor plant health and growth. Control samples were also used at each time point to eliminate confounding parameters due to the plant's normal growth process. After harvesting, the plant leaves were extracted using aq. MeOH (70:30, v/v) and analyzed via UPLC-QToF-MS, using a C18 column in both ionization modes (±ESI). The data-independent (DIA/bbCID) acquisition mode was employed, and the data were analyzed by MS-DIAL. Statistical analysis, including multivariate and trend analysis for longitudinal monitoring, were employed to highlight the differentiated features among the controls and treated plants as well as the time-point sequence. Metabolites related to plant growth belonging to several chemical classes were identified, proving the efficacy of the fertilizer product. Furthermore, the efficiency of the analytical and statistical workflows utilized was demonstrated.

Vishniacozyma victoriae: An endophytic antagonist yeast of kiwifruit with biocontrol effect to Botrytis cinerea

Botrytis cinerea is a pathogenic fungus to fruit, biocontrol is a promising approach to relieve this issue. In this study, Vishniacozyma victoriae is an endophytic yeast extracted from kiwifruit, was used to enhance the resistance of host to B. cinerea. The results showed that lesion diameter of the kiwifruit inoculated with B. cinerea was 55.16 %, 50.57 %, and 48.07 % lower than that of inoculated with V. victoriae + B. cinerea on 4th, 8th, and 12th day, respectively. On 12th day, the total organic acid content and energy charge of kiwifruit inoculated with B. cinerea were 19.25 % and 7.95 % lower than those inoculated with V. victoriae + B. cinerea. These indicated that V. victoriae used the organic acids and energy of host to colonize in the wound, which prevented B. cinerea from contacting the host. Accordingly, V. victoriae is a promising biocontrol yeast to inhibit the infection of B. cinerea on kiwifruit.

Characterization of the Polar Profile of Bacon and Fuerte Avocado Fruits by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry: Distribution of Non-structural Carbohydrates, Quinic Acid, and Chlorogenic Acid between Seed, Mesocarp, and Exocarp at Different Ripening Stages

Avocado fruit growth and development, unlike that of other fruits, is characterized by the accumulation of oil and C7 sugars (in most fruits, the carbohydrates that prevail are C6). There are five essential carbohydrates which constitute 98% of the total content of soluble sugars in this fruit; these are fructose, glucose, sucrose, d-mannoheptulose, and perseitol, which together with quinic acid and chlorogenic acid have been the analytes under study in this work. After applying an efficient extraction procedure, a novel methodology based on hydrophilic interaction liquid chromatography coupled to mass spectrometry was applied to determine the levels of these seven substances in tissues─exocarp, seed, and mesocarp─from avocado fruits of two different varieties scarcely studied, Bacon and Fuerte, at three different ripening stages. Quantitative characterization of the selected tissues was performed, and the inter-tissue distribution of metabolites was described. For both varieties, d-mannoheptulose was the major component in the mesocarp and exocarp, whereas perseitol was predominant in the seed, followed by sucrose and d-mannoheptulose. Sucrose was found to be more abundant in seed tissues, with much lower concentrations in avocado mesocarp and exocarp. Quinic acid showed a predominance in the exocarp, and chlorogenic acid was exclusively determined in exocarp samples.

Metabolic Profiling and Potential Taste Biomarkers of Two Rambutans during Maturation

The metabolite-caused taste variation during rambutan maturation is unknown due to a lack of systematic investigation of all components. In this study, three growing stages, including unripe (S1), half-ripe (S2), and full-ripe (S3) BY2 and BY7 rambutans were compared and profiled by UPLC-MS/MS-based widely targeted metabolomics analysis. We demonstrated that the sugar-acid ratios of two rambutans were greatly improved between the S2 and S3 stages. A total of 821 metabolites were identified, including 232, 205, 204, and 12 differential metabolites (DMs) in BY2-S1 vs. BY2-S2, BY2-S2 vs. BY2-S3, BY7-S1 vs. BY7-S2, and BY7-S2 vs. BY7-S3, respectively. A correlation analysis showed that gamma-aminobutyric acid (GABA) could be the sugar-acid ratio biomarker of BY2 rambutan. Methionine (Met), alanine (Ala), and S-methyl-L-cysteine (SMC) could be total amino acid biomarkers of BY2 and BY7 rambutans. In addition, UPLC-MS/MS-based quantitative verification of the above biomarkers exhibited the same variations as metabolomics analysis. This study not only provides useful nutritive information on rambutans but also valuable metabolic data for rambutan breeding strategies.

Pharmacological insights into the multifaceted biological properties of quinic acid

Quinic acid is a cyclohexanecarboxylic acid contained in the extracts of several parts of medicinal plants including Haematocarpus validus, Hypericum empetrifolium, Achillea pseudoaleppica, Rumex nepalensis, Phagnalon saxatile subsp. saxatile, Coffea arabica, Ziziphus lotus L, and Artemisia annua L … etc. Currently, in vitro and in vivo pharmacological studies showed that quinic acid exhibits various biological activities, such as antioxidant, antidiabetic, anticancer activity, antimicrobial, antiviral, aging, protective, anti-nociceptive and analgesic effects. Indeed, QA possesses an important antibacterial effect which could be explained by the fact that this molecule modules the functions of ribosomes and the synthesis of aminoacyl-tRNAs, modifications the levels of glycerophospholipids and fatty acids and disruption of the oxidative phosphorylation pathway thereby causing interference with membrane fluidity. The antidiabetic activity of AQ is achieved by stimulation of insulin secretion via the mobilization of Ca2+ from intracellular reserves and the increase in the NAD(P)H/NAD(P)+ ratio. Its anticancer effect is through the promotion of apoptosis, inhibition of activator protein 1 (AP-1) and signaling pathways involving protein kinase C (PKC) and certain mitogen-activated protein kinases (MAPKs), resulting in the downregulation of matrix metallopeptidase 9 (MMP-9) expression. Therefore, this review describes the main research work carried out on the biological properties of AQ and the mechanism of action underlying some of these effects, as well as the investigations of the main pharmacokinetic studies.

A missense mutation in WRKY32 converts its function from a positive regulator to a repressor of photomorphogenesis

CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) mediates various cellular and physiological processes in plants by targeting a large number of substrates for ubiquitination and degradation. In this study, we reveal that a substitution of Pro for Leu at amino acid position 409 in WRKY32 largely suppresses the short hypocotyls and expanded cotyledon phenotypes of cop1-6. WRKY32^P409L promotes hypocotyl growth and inhibits the opening of cotyledons in Arabidopsis. Loss of WRKY32 function mutant seedlings display elongated hypocotyls, whereas overexpression of WRKY32 leads to shortened hypocotyls. WRKY32 directly associates with the promoter regions of HY5 to activate its transcription. COP1 interacts with and targets WRKY32 for ubiquitination and degradation in darkness. WRKY32^P409L exhibits enhanced DNA binding ability and affects the expression of more genes compared with WRKY32 in Arabidopsis. Our results not only reveal the basic role for WRKY32 in promoting photomorphogenesis, but also provide insights into manipulating plant growth by engineering key components of light signaling.

Opposite trends of glycosides and alkaloids in Dendrobium nobile of different age based on UPLC-Q/TOF-MS combined with multivariate statistical analyses

INTRODUCTION

Alkaloids and glycosides are the active ingredients of the herb Dendrobium nobile, which is used in traditional Chinese medicine. The pharmacological effects of alkaloids include neuroprotective effects and regulatory effects on glucose and lipid metabolism, while glycosides improve the immune system. The pharmacological activities of the above chemical components are significantly different. In practice, the stems of 3-year-old D. nobile are usually used as the main source of Dendrobii Caulis. However, it has not been reported whether this harvesting time is appropriate.

OBJECTIVE

The aim of this study was to compare the chemical characteristics of D. nobile in different growth years (1-3 years).

METHODS

In this study, ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS) was employed to analyze the constituents of D. nobile. The relative abundance of each constituent was analyzed with multivariate statistical analyses to screen the characteristic constituents that contributed to the characterization and classification of D. nobile. Dendrobine, a component of D. nobile that is used for quality control according to the Chinese Pharmacopoeia, was assayed by gas chromatography.

RESULTS

As a result, 34 characteristic constituents (VIP > 2) were identified or tentatively identified as alkaloids and glycosides based on MS/MS data. Moreover, the content of alkaloids decreased over time, whereas the content of glycosides showed the opposite trend. The absolute quantification of dendrobine was consistent with the metabolomics results.

CONCLUSION

Our findings provide valuable information to optimize the harvest period and a reference for the clinical application of D. nobile.

The Effect of Hydrothermal Treatment on Metabolite Composition of Hass Avocados Stored in a Controlled Atmosphere

Avocado cv. Hass consumption has expanded worldwide given its nutritional, sensory, and functional attributes. In this work, avocado fruit from two harvests was subjected to hydrothermal treatment (38 °C for 1 h) or left untreated (control) and then stored for 30 and 50 days in a controlled atmosphere (4 kPa O₂ and 6 kPa CO₂ at 7 °C) (HTCA and CA, respectively) with subsequent ripening at ~20 °C. The fruit was evaluated for primary and secondary metabolites at harvest, after storage, and after reaching edible ripeness. A decrease from harvest to edible ripeness in mannoheptulose and perseitol was observed while β-sitosterol, hydrophilic and lipophilic antioxidant activity (H-AOX, L-AOX), abscisic acid, and total phenolics (composed of p-coumaric and caffeic acids such as aglycones or their derivatives) increased. HTCA fruit at edible ripeness displayed higher contents of mannoheptulose, perseitol, β-sitosterol, L-AOX, caffeic acid, and p-coumaric acid derivatives, while CA fruit presented higher contents of α-tocopherol, H-AOX, and syringic acid glycoside for both harvests and storage times. The results indicate that a hydrothermal treatment prior to CA enables fruit of high nutritional value characterized by enhanced content of phenolic compounds at edible ripeness to reach distant markets.

Different Metabolic Roles for Alternative Oxidase in Leaves of Palustrine and Terrestrial Species

The alternative oxidase pathway (AOP) is associated with excess energy dissipation in leaves of terrestrial plants. To address whether this association is less important in palustrine plants, we compared the role of AOP in balancing energy and carbon metabolism in palustrine and terrestrial environments by identifying metabolic relationships between primary carbon metabolites and AOP in each habitat. We measured oxygen isotope discrimination during respiration, gas exchange, and metabolite profiles in aerial leaves of ten fern and angiosperm species belonging to five families organized as pairs of palustrine and terrestrial species. We performed a partial least square model combined with variable importance for projection to reveal relationships between the electron partitioning to the AOP (τa) and metabolite levels. Terrestrial plants showed higher values of net photosynthesis (AN) and τa, together with stronger metabolic relationships between τa and sugars, important for water conservation. Palustrine plants showed relationships between τa and metabolites related to the shikimate pathway and the GABA shunt, to be important for heterophylly. Excess energy dissipation via AOX is less crucial in palustrine environments than on land. The basis of this difference resides in the contrasting photosynthetic performance observed in each environment, thus reinforcing the importance of AOP for photosynthesis.

Modifying Carbohydrate Supply to Fruit during Development Changes the Composition and Flavour of Actinidia chinensis var. chinensis 'Zesy002' Kiwifruit

Consumer acceptance of fruit is determined by size, flavour and ripeness. In this study we investigated how altering the carbohydrate supply to Actinidia chinensis var. chinensis 'Zesy002' kiwifruit altered the balance between growth and accumulation of metabolites. Canes were phloem girdled and fruit thinned to a leaf-to-fruit ratio (L:F) of either 2 (Low carbohydrate) or 6 (High carbohydrate) at either 38 (Early) or 86 (Late) days after anthesis (DAA) and compared with ungirdled control canes with a L:F of 3. Fruit growth, metabolite accumulation, cytokinin concentrations and maturation were monitored and the sensory attributes of ripe fruit were assessed. The final weight of Early-High and Late-High carbohydrate fruit was 38% and 16% greater compared with control fruit. High carbohydrate fruit had increased starch, soluble sugar and cytokinin concentrations and fruit began to mature earlier and those with a Low carbohydrate had decreased concentrations and matured later compared with control fruit. Control fruit were described by consumers as more acidic and under-ripe compared with those from Early-High carbohydrate canes, but as sweeter than those from Low carbohydrate canes. This study showed that carbohydrate supply can have a major impact on the growth, sugar accumulation and maturity of 'Zesy002' fruit sinks.

Comparison of fruit morphology and nutrition metabolism in different cultivars of kiwifruit across developmental stages

Kiwifruit (Actinidia) is becoming increasingly popular worldwide due to its favorable flavour and high vitamin C content. However, quality parameters vary among cultivars. To determine the differences in quality and metabolic parameters of kiwifruit, we monitored the growth processes of 'Kuilv' (Actinidia arguta), 'Hongyang' (Actinidia chinensis) and 'Hayward' (Actinidia deliciosa). We found that 'Kuilv' required the shortest time for fruit development, while 'Hayward' needed the longest time to mature. The fruit size of 'Hayward' was the largest and that of 'Kuilv' was the smallest. Furthermore, 'Hongyang' showed a double-S shape of dry matter accumulation, whereas 'Kuilv' and 'Hayward' showed a linear or single-S shape pattern of dry matter accumulation during development. The three cultivars demonstrated the same trend for total soluble solids accumulation, which did not rise rapidly until 90-120 days after anthesis. However, the accumulation of organic acids and soluble sugars varied among the cultivars. During later fruit development, the content of glucose, fructose and quinic acid in 'Kuilv' fruit was far lower than that in 'Hongyang' and 'Hayward'. On the contrary, 'Kuilv' had the highest sucrose content among the three cultivars. At maturity, the antioxidative enzymatic systems were significantly different among the three kiwifruit cultivars. 'Hongyang' showed higher activities of superoxide dismutase than the other cultivars, while the catalase content of 'Hayward' was significantly higher than that of 'Hongyang' and 'Kuilv'. These results provided knowledge that could be implemented for the marketing, handling and post-harvest technologies of the different kiwifruit cultivars.

Experimental races of Capsicum annuum cv. jalapeño: Chemical characterization and classification by 1H NMR/machine learning

This work reports on the metabolic fingerprinting of ten new races of Capsicum annuum cv. jalapeño using ¹H NMR based metabolomics coupled to machine learning projections. Ten races were classified and evaluated according to their differential metabolites, variables of commercial interest and by multivariate data analysis/machine learning algorithm. According to our results, experimental races of jalapeño peppers exhibited differences in carbohydrate, amino acid, nucleotide and organic acid contents. Forty-eight metabolites were identified by 1D and 2D NMR and the differential metabolites were quantified by qNMR. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) separated the studied races into two groups. The group A included the races Colosus, Emperador, Fundador and Rayo whereas the group B included the races Don Benito, SMJ 1416, SMJ 1417, SMJ 1423, SMJ 145 and STAM J0904. OPLS-DA revealed that levels of citric acid in group A were higher than in group B, while the levels of asparagine, fumaric acid, GABA, glucose, malic acid, pyruvic, quinic acid, sucrose and tryptophan were higher in the group B. Remarkably, ascorbic acid was exclusively found in the race Colosus. Random forest model revealed the diversity of the experimental races and the similarity rate with the well-established races. The most relevant variables used to generate a model were length, weight, yield, width, xylose content and organic acids content.

Bioactive compounds, antioxidant and antimicrobial activities of extracts from different plant parts of two Ziziphus Mill. species

Ziziphus lotus L. (Lam.) and Z. mauritiana Lam., as a widespread species in Tunisia, are well known for their medicinal and food uses. The aim of the present study was to screen the content of total polyphenols, flavonoids, and condensed tannins together with the radical scavenging capacity and the antimicrobial activity of leaves, fruits and seeds extracts of Z. lotus and Z. mauritiana from different localities. Results showed that leaves extracts presented the highest phenolic compounds content for both species. Furthermore, LC-ESI-MS analysis allowed the identification of 28 bioactive compounds regardless of species and organs, with the predominance of quinic acid and rutin. Leaves extract of Z. mauritiana possessed the highest total antioxidant capacity. The antimicrobial tests showed that leaves extracts of Z. mauritiana and Z. lotus from Oued Esseder exhibited the highest activity against four bacterial strains (Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium and Escherichia coli). The main results showed that the studied species of Ziziphus genus are an excellent source of natural bioactive molecules that could be an interesting material for industrial and food purposes.

Characterization of Organic Acid Metabolism and Expression of Related Genes During Fruit Development of Actinidia eriantha 'Ganmi 6'

Studies on organic acid metabolism have been mainly concentrated on the fruit, whereas, few have focused on the mechanism of high organic acids content in the fruit of Actinidia eriantha. Fruits of 'Ganmi 6' harvested at eleven developmental periods were used as materials. The components and content of organic acids were determined by high-performance liquid chromatography (HPLC) system, the activities of the related enzyme were detected, and gene expression levels were measured by quantitative real-time PCR (qRT-PCR). Components of ascorbic acid (AsA) and eight kinds of organic acids were detected. These results showed that quinic acid and citric acid were the main organic acids in the fruit of 'Ganmi 6'. Correlation analysis showed that NADP-Quinate dehydrogenase (NADP-QDH), NADP-Shikimate dehydrogenase (NADP-SDH), and Cyt-Aconitase (Cyt-Aco) may be involved in regulating organic acids biosynthesis. Meanwhile, the SDH gene may play an important role in regulating the accumulation of citric acid. In this study, the activities of NADP-SDH, Mit-Aconitase (Mit-Aco), and NAD-Isocitrate dehydrogenase (NAD-IDH) were regulated by their corresponding genes at the transcriptional level. The activity of Citrate synthase (CS) may be affected by post-translational modification. Our results provided new insight into the characteristics of organic acid metabolism in the fruit of A. eriantha.

Comparison Among Five Eucalyptus Species Based on Their Leaf Contents of Some Primary and Secondary Metabolites

Background:

Eucalyptus belongs to the Myrtaceae family. It is the most planted hardwood forest crop worldwide, representing a global renewable resource of fiber, pharmaceuticals and energy.

Objective:

To compare the five species, E. maidenii, E. robusta, E. citriodora, E. tereticornis and E. camaldulensis, seeking for the richest source of nutrients and pharmaceuticals.

Methodology:

Eucalyptus samples were subjected to some chemical determinations for both primary and secondary metabolites to verify their nutritional and pharmaceutical importance related to different extracts. GC-MS analysis was applied to detect the presence of some individual phenolic constituents in their leaves.

Results:

E. robusta recorded the maximum contents of carbohydrates (40.07%) and protein (31.91%). While E. camaldulensis contained the highest contents of total phenolic compounds (46.56 mg/g), tannins (40.01 mg/g) and antioxidant activities assayed by the phosphomolybednum method (57.60 mg/g), followed by E. citridora. However, E. tereticornis exhibited the highest reducing power ability (151.23 mg/g). The GC-MS highlighted 20 phenolic constituents and antioxidants which varied in their abundance in Eucalyptus leaves, 8 individual phenolics (hydroquinone, hesperitin, pyrogallol, resorcinol, protocatechuic acid, naringenin, chlorogenic acid and catechin) were maximally recorded with E. camaldulensis and secondly, with E. citridora in case of at least 5 components. Nevertheless, gallic and quinic acids were more abundant in the leaves of E. tereticornis, which may explain its high corresponding reducing powers.

Conclusion:

Acetone-water combination has enhanced phenolics extraction from Eucalyptus tissues. This is the first report aiming to compare between the aforementioned Eucalyptus species highlighting either their nutritional or medicinal importance.

Genotypic Variation in the Root and Shoot Metabolite Profiles of Wheat (Triticum aestivum L.) Indicate Sustained, Preferential Carbon Allocation as a Potential Mechanism in Phosphorus Efficiency

Changes in the levels of plant metabolites in response to nutrient deficiency is indicative of how plants utilize scarce resources. In this study, changes in the metabolite profile of roots and shoots of wheat genotypes differing in phosphorus use efficiency (PUE) was investigated. Under low P supply and at 28 days after sowing (DAS), the wheat breeding line, RAC875 (P efficient) produced 42% more shoot biomass than the wheat variety, and Wyalkatchem (P inefficient). Significant changes in the metabolite profile in leaves and roots were observed under low P supply and significant genotypic variation was evident. Under low P supply, an increase in raffinose and 1-kestose was evident in roots of both wheat genotypes, with RAC875 accumulating more when compared to Wyalkatchem. There was no significant increase in raffinose and 1-kestose in leaves when plants were grown under P deficiency. P deficiency had no significant impact on the levels of sucrose, maltose, glucose and fructose in both genotypes, and while phosphorylated sugars (glucose-6-P and fructose-6-P) remained unchanged in RAC875, in Wyalkatchem, glucose-6-P significantly decreased in roots, and fructose-6-P significantly decreased in both leaves and roots. Glycerol-3-P decreased twofold in roots of both wheat genotypes in response to low P. In roots, RAC875 exhibited significantly lower levels of fumarate, malate, maleate and itaconate than Wyalkatchem, while low P enhanced organic acid exudation in RAC875 but not in Wyalkatchem. RAC875 showed greater accumulation of aspartate, glutamine and β-alanine in leaves than Wyalkatchem under low P supply. Greater accumulation of raffinose and 1-kestose in roots and aspartate, glutamine and β-alanine in leaves appears to be associated with enhanced PUE in RAC875. Glucose-6-P and fructose-6-P are important for glycolysis, thus maintaining these metabolites would enable RAC875 to maintain carbohydrate metabolism and shoot biomass under P deficiency. The work presented here provides evidence that differences in metabolite profiles can be observed between wheat varieties that differ in PUE and key metabolic pathways are maintained in the efficient genotype to ensure carbon supply under P deficiency.

Fruit Salad in the Lab: Comparing Botanical Species to Help Deciphering Fruit Primary Metabolism

Although fleshy fruit species are economically important worldwide and crucial for human nutrition, the regulation of their fruit metabolism remains to be described finely. Fruit species differ in the origin of the tissue constituting the flesh, duration of fruit development, coordination of ripening changes (climacteric vs. non-climacteric type) and biochemical composition at ripeness is linked to sweetness and acidity. The main constituents of mature fruit result from different strategies of carbon transport and metabolism. Thus, the timing and nature of phloem loading and unloading can largely differ from one species to another. Furthermore, accumulations and transformations of major soluble sugars, organic acids, amino acids, starch and cell walls are very variable among fruit species. Comparing fruit species therefore appears as a valuable way to get a better understanding of metabolism. On the one hand, the comparison of results of studies about species of different botanical families allows pointing the drivers of sugar or organic acid accumulation but this kind of comparison is often hampered by heterogeneous analysis approaches applied in each study and incomplete dataset. On the other hand, cross-species studies remain rare but have brought new insights into key aspects of primary metabolism regulation. In addition, new tools for multi-species comparisons are currently emerging, including meta-analyses or re-use of shared metabolic or genomic data, and comparative metabolic flux or process-based modeling. All these approaches contribute to the identification of the metabolic factors that influence fruit growth and quality, in order to adjust their levels with breeding or cultural practices, with respect to improving fruit traits.

Structural and biochemical approaches uncover multiple evolutionary trajectories of plant quinate dehydrogenases

Quinate is produced and used by many plants in the biosynthesis of chlorogenic acids (CGAs). Chlorogenic acids are astringent and serve to deter herbivory. They also function as antifungal agents and have potent antioxidant properties. Quinate is produced at a branch point of shikimate biosynthesis by the enzyme quinate dehydrogenase (QDH). However, little information exists on the identity and biochemical properties of plant QDHs. In this study, we utilized structural and bioinformatics approaches to establish a QDH-specific primary sequence motif. Using this motif, we identified QDHs from diverse plants and confirmed their activity by recombinant protein production and kinetic assays. Through a detailed phylogenetic analysis, we show that plant QDHs arose directly from bifunctional dehydroquinate dehydratase-shikimate dehydrogenases (DHQD-SDHs) through different convergent evolutionary events, illustrated by our findings that eudicot and conifer QDHs arose early in vascular plant evolution whereas Brassicaceae QDHs emerged later. This process of recurrent evolution of QDH is further demonstrated by the fact that this family of proteins independently evolved NAD+ and NADP+ specificity in eudicots. The acquisition of QDH activity by these proteins was accompanied by the inactivation or functional evolution of the DHQD domain, as verified by enzyme activity assays and as reflected in the loss of key DHQD active site residues. The implications of QDH activity and evolution are discussed in terms of plant growth and development.

Characterization and quantification of flavonoids and organic acids over fruit development in American cranberry (Vaccinium macrocarpon) cultivars using HPLC and APCI-MS/MS

Cranberry flavonoids, including anthocyanins, flavonol glycosides and proanthocyanidins, and organic acids were characterized and quantified by HPLC and LC-MS/MS during fruit development and ripening in eight cranberry cultivars. Anthocyanin biosynthesis initiated at early fruit development and reached highest level in mature fruit, with significant differences between cultivars. Major flavonol glycosides, including the most abundant quercetin-3-galactoside and myricetin-3-galactoside, showed consistent concentrations during the season with moderate fluctuation, and were at similar levels in mature fruits of the eight cultivars. Proanthocyanidins declined during fruit development and then increased slightly in later maturation stages. Levels of various proanthocyanidin oligomers/polymers with different degree-of-polymerization were highly correlated within a cultivar during fruit development. Cultivars with coancestry exhibited similar levels (high/low) of anthocyanins or proanthocyanidins, indicating genetic effects on biosynthesis of such flavonoids. All cultivars showed similar levels of malic and citric acids, and declining levels of quinic acid during fruit development. Benzoic acid was extremely low early in the season and increased sharply during fruit ripening. Levels of quinic and citric acids were significantly different among cultivars in the mature fruit. Concentrations of proanthocyanidins, anthocyanins, quinic acid and benzoic acid have a strong developmental association in developing ovaries.

Untargeted MS-based small metabolite identification from the plant leaves and stems of Impatiens balsamina

The identification of plant metabolites is very important for the understanding of plant physiology including plant growth, development and defense mechanism, particularly for herbal medicinal plants. The metabolite profile could possibly be used for future drug discovery since the pharmacological activities of the indigenous herbs have been proven for centuries. An untargeted mass spectrometric approach was used to identify metabolites from the leaves and stems of Impatiens balsamina using LC-DAD-MS/MS. The putative compounds are mostly from the groups of phenolic, organic and amino acids which are essential for plant growth and as intermediates for other compounds. Alanine appeared to be the main amino acid in the plant because many alanine derived metabolites were detected. There are also several secondary metabolites from the groups of benzopyrones, benzofuranones, naphthoquinones, alkaloids and flavonoids. The widely reported bioactive components such as kaempferol, quercetin and their glycosylated, lawsone and its derivatives were detected in this study. The results also revealed that aqueous methanol could extract flavonoids better than water, and mostly, flavonoids were detected from the leaf samples. The score plots of component analysis show that there is a minor variance in the metabolite profiles of water and aqueous methanolic extracts with 21.5 and 30.5% of the total variance for the first principal component at the positive and negative ion modes, respectively.

Metabolic profiling reveals altered pattern of central metabolism in navel orange plants as a result of boron deficiency

We focused on the changes of metabolite profiles in navel orange plants under long-term boron (B) deficiency using a gas chromatography-mass spectrometry (GC-MS) approach. Curling of the leaves and leaf chlorosis were observed only in the upper leaves (present before start of the treatment) of B-deficient plants, while the lower leaves (grown during treatment) did not show any visible symptoms. The metabolites with up-accumulation in B-deficient leaves were mainly proline, l-ornithine, lysine, glucoheptonic acid, fucose, fumarate, oxalate, quinate, myo-inositol and allo-inositol, while the metabolites with down-accumulation in B-deficient leaves were mainly serine, asparagine, saccharic acid, citrate, succinate, shikimate and phytol. The levels of glucose and fructose were increased only in the upper leaves by B deficiency, while starch content was increased in all the leaves and in roots. The increased levels of malate, ribitol, gluconic acid and glyceric acid occurred only in the lower leaves of B-deficient plants. The increased levels of phenols only in the upper leaves indicated that the effects of B on phenol metabolism in citrus plants may be a consequence of disruptions in leaf structure. Metabolites with opposite reactions in upper and lower leaves were mainly glutamine, glycine and pyrrole-2-carboxylic acid. To our knowledge, the phenomena of allo-inositol even higher than myo-inositol occurred characterized for the first time in this species. These results suggested that the altered pattern of central metabolism may be either specific or adaptive responses of navel orange plants to B deficiency.

The shikimate dehydrogenase family: functional diversity within a conserved structural and mechanistic framework

Shikimate dehydrogenase (SDH) catalyzes the NADPH-dependent reduction of 3-deydroshikimate to shikimate, an essential reaction in the biosynthesis of the aromatic amino acids and a large number of other secondary metabolites in plants and microbes. The indispensible nature of this enzyme makes it a potential target for herbicides and antimicrobials. SDH is the archetypal member of a large protein family, which contains at least four additional functional classes with diverse metabolic roles. The different members of the SDH family share a highly similar three-dimensional structure and utilize a conserved catalytic mechanism, but exhibit distinct substrate preferences, making the family a particularly interesting system for studying modes of substrate recognition used by enzymes. Here, we review our current understanding of the biochemical and structural properties of each of the five previously identified SDH family functional classes.

Molecular characterization of quinate and shikimate metabolism in Populus trichocarpa

The shikimate pathway leads to the biosynthesis of aromatic amino acids essential for protein biosynthesis and the production of a wide array of plant secondary metabolites. Among them, quinate is an astringent feeding deterrent that can be formed in a single step reaction from 3-dehydroquinate catalyzed by quinate dehydrogenase (QDH). 3-Dehydroquinate is also the substrate for shikimate biosynthesis through the sequential actions of dehydroquinate dehydratase (DQD) and shikimate dehydrogenase (SDH) contained in a single protein in plants. The reaction mechanism of QDH resembles that of SDH. The poplar genome encodes five DQD/SDH-like genes (Poptr1 to Poptr5), which have diverged into two distinct groups based on sequence analysis and protein structure prediction. In vitro biochemical assays proved that Poptr1 and -5 are true DQD/SDHs, whereas Poptr2 and -3 instead have QDH activity with only residual DQD/SDH activity. Poplar DQD/SDHs have distinct expression profiles suggesting separate roles in protein and lignin biosynthesis. Also, the QDH genes are differentially expressed. In summary, quinate (secondary metabolism) and shikimate (primary metabolism) metabolic activities are encoded by distinct members of the same gene family, each having different physiological functions.

Biochemical and structural characterisation of dehydroquinate synthase from the New Zealand kiwifruit Actinidia chinensis

One of the novel aspects of kiwifruit is the presence of a high level of quinic acid which contributes to the flavour of the fruit. Quinic acid metabolism intersects with the shikimate pathway, which is responsible for the de novo biosynthesis of primary and secondary aromatic metabolites. The gene encoding the enzyme which catalyses the second step of the shikimate pathway, dehydroquinate synthase (DHQS), from the New Zealand kiwifruit Actinidia chinensis was identified, cloned and expressed. A. chinensis DHQS was activated by divalent metal ions, and was found to require NAD(+) for catalysis. The protein was crystallised and the structure was solved, revealing a homodimeric protein. Each monomer has a NAD(+) binding site nestled between the distinct N- and C-terminal domains. In contrast to other microbial DHQSs, which show an open conformation in the absence of active site ligands, A. chinensis DHQS adopts a closed conformation. This is the first report of the structure of a DHQS from a plant source.

Fruit development of the diploid kiwifruit, Actinidia chinensis 'Hort16A'

BACKGROUND

With the advent of high throughput genomic tools, it is now possible to undertake detailed molecular studies of individual species outside traditional model organisms. Combined with a good understanding of physiological processes, these tools allow researchers to explore natural diversity, giving a better understanding of biological mechanisms. Here a detailed study of fruit development from anthesis through to fruit senescence is presented for a non-model organism, kiwifruit, Actinidia chinensis ('Hort16A').

RESULTS

Consistent with previous studies, it was found that many aspects of fruit morphology, growth and development are similar to those of the model fruit tomato, except for a striking difference in fruit ripening progression. The early stages of fruit ripening occur as the fruit is still growing, and many ripening events are not associated with autocatalytic ethylene production (historically associated with respiratory climacteric). Autocatalytic ethylene is produced late in the ripening process as the fruit begins to senesce.

CONCLUSION

By aligning A. chinensis fruit development to a phenological scale, this study provides a reference framework for subsequent physiological and genomic studies, and will allow cross comparison across fruit species, leading to a greater understanding of the diversity of fruits found across the plant kingdom.