Analysis of metabolic flux using dynamic labeling and metabolic modeling

Metabolic fluxes and the capacity to modulate them are a crucial component of the ability of the plant cell to react to environmental perturbations. Our ability to quantify them and to attain information concerning the regulatory mechanisms which control them is therefore essential to understand and influence metabolic networks. For all but the simplest of flux measurements labelling methods have proven to be the most informative. Both steady-state and dynamic labelling approaches having been adopted in the study of plant metabolism. Here the conceptual basis of these complementary approaches, as well as their historical application in microbial, mammalian and plant sciences are reviewed and an update on technical developments in label distribution analyses is provided. This is supported by illustrative cases studies involving the kinetic modelling of secondary metabolism. One issue that is particularly complex in the analysis of plant fluxes is the extensive compartmentation of the plant cell. This problem is discussed from both theoretical and experimental perspectives and the current approaches used to address it are assessed. Finally, current limitations and future perspectives of kinetic modelling of plant metabolism are discussed

The use of metabolomics to dissect plant responses to abiotic stresses

Plant metabolism is perturbed by various abiotic stresses. As such the metabolic network of plants must be reconfigured under stress conditions in order to allow both the maintenance of metabolic homeostasis and the production of compounds that ameliorate the stress. The recent development and adoption of metabolomics and systems biology approaches enable us not only to gain a comprehensive overview, but also a detailed analysis of crucial components of the plant metabolic response to abiotic stresses. In this review we introduce the analytical methods used for plant metabolomics and describe their use in studies related to the metabolic response to water, temperature, light, nutrient limitation, ion and oxidative stresses. Both similarity and specificity of the metabolic responses against diverse abiotic stress are evaluated using data available in the literature. Classically discussed stress compounds such as proline, gamma-amino butyrate and polyamines are reviewed, and the widespread importance of branched chain amino acid metabolism under stress condition is discussed. Finally, where possible, mechanistic insights into metabolic regulatory processes are discussed

High-to-low CO2 acclimation reveals plasticity of the photorespiratory pathway and indicates regulatory links to cellular metabolism of Arabidopsis

Background: Photorespiratory carbon metabolism was long considered as an essentially closed and nonregulated pathway with little interaction to other metabolic routes except nitrogen metabolism and respiration. Most mutants of this pathway cannot survive in ambient air and require CO 2-enriched air for normal growth. Several studies indicate that this CO 2 requirement is very different for individual mutants, suggesting a higher plasticity and more interaction of photorespiratory metabolism as generally thought. To understand this better, we examined a variety of high- and low-level parameters at 1% CO 2 and their alteration during acclimation of wild-type plants and selected photorespiratory mutants to ambient air. Methodology and Principal Findings: The wild type and four photorespiratory mutants of Arabidopsis thaliana (Arabidopsis) were grown to a defined stadium at 1% CO 2 and then transferred to normal air (0.038% CO 2). All other conditions remained unchanged. This approach allowed unbiased side-by-side monitoring of acclimation processes on several levels. For all lines, diel (24 h) leaf growth, photosynthetic gas exchange, and PSII fluorescence were monitored. Metabolite profiling was performed for the wild type and two mutants. During acclimation, considerable variation between the individual genotypes was detected in many of the examined parameters, which correlated with the position of the impaired reaction in the photorespiratory pathway. Conclusions: Photorespiratory carbon metabolism does not operate as a fully closed pathway. Acclimation from high to low CO 2 was typically steady and consistent for a number of features over several days, but we also found unexpected short-term events, such as an intermittent very massive rise of glycine levels after transition of one particular mutant to ambient air. We conclude that photorespiration is possibly exposed to redox regulation beyond known substrate-level effects. Additionally, our data support the view that 2-phosphoglycolate could be a key regulator of photosynthetic-photorespiratory metabolism as a whole. © 2012 Timm et al

Different coping strategies amongst individuals with grandiose and vulnerable narcissistic traits

OBJECTIVE: This study explored the relationships between coping with stress responses and grandiose and vulnerable narcissist traits. METHOD: A community sample of 170 adults (113 female) participated in this study. A cross-sectional design was employed that utilized self-report measures of trait anxiety, social desirability, coping with stress responses, and pathological narcissism. RESULTS: Regression models indicated that both grandiose and vulnerable narcissism traits are significantly associated with, in opposing directions, behavioural disengagement responses to stress when controlling for trait anxiety and social desirability. Vulnerable narcissism traits were significantly associated with the use of denial as coping with stress response when controlling for the same factors. CONCLUSION: These findings provide further evidence of the discriminant validity of the Pathological Narcissism Inventory and inform our understanding of the differences that grandiose and vulnerable narcissistic traits have on coping

Decreased expression of plastidial adenylate kinase in potato tubers results in an enhanced rate of respiration and a stimulation of starch synthesis that is attributable to post-translational redox-activation of ADP-glucose pyrophosphorylase

Adenine nucleotides are of general importance for many aspects of cell function, but their role in the regulation of biosynthetic processes is still unclear. It was previously reported that decreased expression of plastidial adenylate kinase, catalysing the interconversion of ATP and AMP to ADP, leads to increased adenylate pools and starch content in transgenic potato tubers. However, the underlying mechanisms were not elucidated. Here, it is shown that decreased expression of plastidial adenylate kinase in growing tubers leads to increased rates of respiratory oxygen consumption and increased carbon fluxes into starch. Increased rates of starch synthesis were accompanied by post-translational redox-activation of ADP-glucose pyrophosphorylase (AGPase), catalysing the key regulatory step of starch synthesis in the plastid, while there were no substantial changes in metabolic intermediates or sugar levels. A similar increase in post-translational redox-activation of AGPase was found after supplying adenine to wild-type potato tuber discs to increase adenine nucleotide levels. Results provide first evidence for a link between redox-activation of AGPase and adenine nucleotide levels in plants

Intra- and extra-cellular excretion of carboxylates

Carboxylates, such as malate and citrate, are widely acknowledged to have a central role in plant metabolism. They are involved in the production of energy and its storage as well as contributing to the cellular osmolyte pool and participating in the regulation of cellular pH. As we discuss here, recent research has demonstrated the functional importance of carboxylate excretion into the soil, apoplast and vacuole, particular with respect to the regulation of stomatal and root function

The molecular control of tomato fruit quality traits: the trade off between visual attributes, shelf life and nutritional value

Tomato (Solanum lycopersicum) is an established model to study fleshy fruit development and ripening and is an important crop in terms of its economic and nutritional value. Tomato fruit quality is a function of metabolite content which is prone to physiological changes related to fruit development and ripening. It has been described some ripening tomato mutants, delayed fruit deterioration (DFD), non-ripening (NOR) and ripening-inhibitor (RIN) which substantially extend “shelf life” in tomato for up to several months when defined in terms of softening, water loss and resistance to postharvest biotic infection. However, it is not known whether this extension in “shelf life” is in fact a desirable objective from the perspective of nutritional quality of the fruits. The aim of this work was to use a metabolomics approach join to genomic tools to characterize compositional changes (sugars, amino acids, organic acids and carotenoids) of non-softening tomato mutants reported (DFD, NOR and RIN) in comparison with the normally softening fruits (Ailsa Craig and M82) during ripening and postharvest shelf-life. Important results related with ripening gene expression and metabolic evolutions are shown

Transcultural, transdiagnostic, and concurrent validity of a revised Metacognitions about Symptom Control Scale

Anxiety and depression add to the burden of Chronic Fatigue Syndrome (CFS), Fibromyalgia (FM), and Type 1 Diabetes Mellitus (T1DM). Metacognitions play a role in this distress. The Metacognitions about Symptoms Control Scale (MaSCS) measures metacognitive beliefs regarding symptoms but has weaknesses. The current study created a revised MaSCS (MaSCS-R) in English, German, and Arabic versions using CFS, FM, and T1DM samples, and examined the transcultural, transdiagnostic, and concurrent validity of metacognitions about symptom control. This study used data from a total of 563 participants clinically diagnosed with CFS (n = 124; English), FM (n = 348; German), or T1DM (n = 91; Lebanese). CFS and FM data had been used in earlier published studies but were subjected to new analyses. CFS data was used to create the English version of the MaSCS-R, and FM and T1DM data for German and Arabic versions. Metacognitions about worry, anxiety, depression, and symptom severity were measured. The three MaSCS-R versions, consisting of two factors (each with four items), had adequate psychometric properties, possessing configural and metric invariance. Metacognitive factors were associated with distress and symptom severity in all three samples. Metacognitions about symptom control have transcultural, transdiagnostic, and concurrent validity. This is the peer reviewed version of the following article: Fernie, B.A., Aoun, A., Kollman, J., Spada, M.M., and Nikčević, A.V. (2019). Transcultural, transdiagnostic, and concurrent validity of a revised Metacognitions about Symptoms Control Scale. Clinical Psychology and Psychotherapy, which has been published in final form at 10.1002/cpp.2367 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Version