The transition from juvenility through maturation to senescence is a complex process that involves the regulation of longevity. Here, we identify JUNGBRUNNEN1 (JUB1), a hydrogen peroxide (H 2 O 2 )-induced NAC transcription factor, as a central longevity regulator in Arabidopsis thaliana. JUB1 overexpression strongly delays senescence, dampens intracellular H 2 O 2 levels, and enhances tolerance to various abiotic stresses, whereas in jub1-1 knockdown plants, precocious senescence and lowered abiotic stress tolerance are observed. A JUB1 binding site containing a RRYGCCGT core sequence is present in the promoter of DREB2A, which plays an important role in abiotic stress responses. JUB1 transactivates DREB2A expression in mesophyll cell protoplasts and transgenic plants and binds directly to the DREB2A promoter. Transcriptome profiling of JUB1 overexpressors revealed elevated expression of several reactive oxygen species-responsive genes, including heat shock protein and glutathione S-transferase genes, whose expression is further induced by H 2 O 2 treatment. Metabolite profiling identified elevated Pro and trehalose levels in JUB1 overexpressors, in accordance with their enhanced abiotic stress tolerance. We suggest that JUB1 constitutes a central regulator of a finely tuned control system that modulates cellular H 2 O 2 level and primes the plants for upcoming stress through a gene regulatory network that involves DREB2A.

No abstract

Metabolomics is one omics approach that can be used to acquire comprehensive information on the composition of a metabolite pool to provide a functional screen of the cellular state. Studies of the plant metabolome include analysis of a wide range of chemical species with diverse physical properties, from ionic inorganic compounds to biochemically derived hydrophilic carbohydrates, organic and amino acids, and a range of hydrophobic lipid-related compounds. This complexitiy brings huge challenges to the analytical technologies employed in current plant metabolomics programs, and powerful analytical tools are required for the separation and characterization of this extremely high compound diversity present in biological sample matrices. The use of mass spectrometry (MS)-based analytical platforms to profile stress-responsive metabolites that allow some plants to adapt to adverse environmental conditions is fundamental in current plant biotechnology research programs for the understanding and development of stress-tolerant plants. In this review, we describe recent applications of metabolomics and emphasize its increasing application to study plant responses to environmental (stress-) factors, including drought, salt, low oxygen caused by waterlogging or flooding of the soil, temperature, light and oxidative stress (or a combination of them). Advances in understanding the global changes occurring in plant metabolism under specific abiotic stress conditions are fundamental to enhance plant fitness and increase stress tolerance. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:620-649, 2016.

Hydrophilic interaction liquid chromatography (HILIC), although not a new technique, has enjoyed a recent renaissance with the introduction of robust and reproducible stationary phases. It is consequently finding application in metabolomics studies, which have traditionally relied on the stability of reversed phases (RPs), since the biofluids analyzed are predominantly aqueous and thus contain many polar analytes. HILIC's retention of those polar compounds and use of solvents readily compatible with mass spectrometry have seen its increasing adoption in studies of complex aqueous metabolomes. This review describes the stationary phases and their features, surveys HILIC-LC-MS's role in metabolomics experiments, discusses approaches to data extraction and analysis including multivariate analysis, and reviews the literature on HILIC-MS applications in metabolomics.

Natural genetic diversity provides a powerful tool to study the complex interrelationship between metabolism and growth. Profiling of metabolic traits combined with network-based and statistical analyses allow the comparison of conditions and identification of sets of traits that predict biomass. However, it often remains unclear why a particular set of metabolites is linked with biomass and to what extent the predictive model is applicable beyond a particular growth condition. A panel of 97 genetically diverse Arabidopsis (Arabidopsis thaliana) accessions was grown in near-optimal carbon and nitrogen supply, restricted carbon supply, and restricted nitrogen supply and analyzed for biomass and 54 metabolic traits. Correlation-based metabolic networks were generated from the genotype-dependent variation in each condition to reveal sets of metabolites that show coordinated changes across accessions. The networks were largely specific for a single growth condition. Partial least squares regression from metabolic traits allowed prediction of biomass within and, slightly more weakly, across conditions (cross-validated Pearson correlations in the range of 0.27-0.58 and 0.21-0.51 and P values in the range of ,0.001-,0.13 and ,0.001-,0.023, respectively). Metabolic traits that correlate with growth or have a high weighting in the partial least squares regression were mainly condition specific and often related to the resource that restricts growth under that condition. Linear mixed-model analysis using the combined metabolic traits from all growth conditions as an input indicated that inclusion of random effects for the conditions improves predictions of biomass. Thus, robust prediction of biomass across a range of conditions requires condition-specific measurement of metabolic traits to take account of environment-dependent changes of the underlying networks.

Highly mesoporous (Brunauer–Emmett–Teller surface area, SBET > 200 m2 g−1; mesopore volume > 1 cm3 g−1) carbonaceous materials are prepared in a truly sustainable manner, from the naturally occurring polysaccharide alginic acid. This approach yields large mesoporous materials (pore diameter > 14 nm) significantly without the use of a template or carbonization catalyst. The direct thermal decomposition of mesoporous forms of the acidic polysaccharide allows for an extremely flexible material preparation strategy. Materials can be prepared at any desired carbonization temperature (e.g., 200–1000 °C), possessing similar textural properties, but progressively presenting more uniform surface functionality through this temperature range, from more oxygenated surfaces at low temperatures to increasingly aromatic/graphitic‐like surfaces. The high‐temperature material (i.e., 1000 °C), while predominantly amorphous, presents some short range (turbostratic) ordering, providing sufficiently polarizable surfaces on which to perform challenging liquid phase separations of polar sugar analytes.

Metabolomics is a research field used to acquire comprehensive information on the composition of a metabolite pool to provide a functional screen of the cellular state. Studies of the plant metabolome include the analysis of a wide range of chemical species with very diverse physico-chemical properties, and therefore powerful analytical tools are required for the separation, characterization and quantification of this vast compound diversity present in plant matrices. In this review, challenges in the use of mass spectrometry (MS) as a quantitative tool in plant metabolomics experiments are discussed, and important criteria for the development and validation of MS-based analytical methods provided. This article is part of the themed issue ‘Quantitative mass spectrometry’.

Plants usually tolerate drought by producing organic solutes, which can either act as compatible osmolytes for maintaining turgor, or radical scavengers for protecting cellular functions. However, these two properties of organic solutes are often indistinguishable during stress progression. This study looked at individualizing properties of osmotic adjustment vs. osmoprotection in plants, using cowpea as the model species. Two cultivars were grown in well-watered soil, drought conditions, or drought followed by rewatering through fruit formation. Osmoadaptation was investigated in leaves and roots using photosynthetic traits, water homoeostasis, inorganic ions, and primary and secondary metabolites. Multifactorial analyses indicated allocation of high quantities of amino acids, sugars, and proanthocyanidins into roots, presumably linked to their role in growth and initial stress perception. Physiological and metabolic changes developed in parallel and drought/recovery responses showed a progressive acclimation of the cowpea plant to stress. Of the 88 metabolites studied, proline, galactinol, and a quercetin derivative responded the most to drought as highlighted by multivariate analyses, and their correlations with yield indicated beneficial effects. These metabolites accumulated differently in roots, but similarly in leaves, suggesting a more conservative strategy to cope with drought in the aerial parts. Changes in these compounds roughly reflected energy investment in protective mechanisms, although the ability of plants to adjust osmotically through inorganic ions uptake could not be discounted.