Jasmonate‐mediated stomatal closure under elevated CO2 revealed by time‐resolved metabolomics

Foliar stomatal movements are critical for regulating plant water loss and gas exchange. Elevated carbon dioxide (CO₂) levels are known to induce stomatal closure. However, the current knowledge on CO₂ signal transduction in stomatal guard cells is limited. Here we report metabolomic responses of Brassica napus guard cells to elevated CO₂ using three hyphenated metabolomics platforms: gas chromatography‐mass spectrometry (MS); liquid chromatography (LC)‐multiple reaction monitoring‐MS; and ultra‐high‐performance LC‐quadrupole time‐of‐flight‐MS. A total of 358 metabolites from guard cells were quantified in a time‐course response to elevated CO₂ level. Most metabolites increased under elevated CO₂, showing the most significant differences at 10 min. In addition, reactive oxygen species production increased and stomatal aperture decreased with time. Major alterations in flavonoid, organic acid, sugar, fatty acid, phenylpropanoid and amino acid metabolic pathways indicated changes in both primary and specialized metabolic pathways in guard cells. Most interestingly, the jasmonic acid (JA) biosynthesis pathway was significantly altered in the course of elevated CO₂ treatment. Together with results obtained from JA biosynthesis and signaling mutants as well as CO₂ signaling mutants, we discovered that CO₂‐induced stomatal closure is mediated by JA signaling.     

CYP2E1-catalyzed oxidation contributes to the sperm toxicity of 1-bromopropane in mice

1-bromopropane (1-BrP) induces dose- and time-dependent reproductive organ toxicity and reduced sperm motility in rodents. The contribution of cytochrome P4502E1 (CYP2E1) to both 1-BrP metabolism and the induction of male reproductive toxicity was investigated using wild-type (WT) and Cyp2e1-/- mice. In gas uptake inhalation studies, the elimination half-life of [1,2,3-(13)C]-1-BrP was longer in Cyp2e1-/- mice relative to WT (3.2 vs. 1.3 h). Urinary metabolites were identified by 13C nuclear magnetic resonance. The mercapturic acid of 1-bromo-2-hydroxypropane (2OHBrP) was the major urinary metabolite in WT mice, and products of conjugation of 1-BrP with glutathione (GSH) were insignificant. The ratio of GSH conjugation to 2-hydroxylation increased 5-fold in Cyp2e1-/- mice relative to WT. After 1-BrP exposure, hepatic GSH was decreased by 76% in WT mice vs. 47% in Cyp2e1-/- mice. Despite a 170% increase in 1-BrP exposure in Cyp2e1-/- vs. WT mice, sperm motility in exposed Cyp2e1-/- mice did not change relative to unexposed matched controls. This suggests that metabolites produced through CYP2E1-mediated oxidation may be responsible for 1-BrP-induced sperm toxicity. Both 1-BrP and 2OHBrP inhibited the motility of sperm obtained from WT mice in vitro. However, only 2OHBrP reduced the motility of sperm obtained from Cyp2e1-/- mice in vitro, suggesting that conversion of parent compound to 2OHBrP within the spermatozoa may contribute, at least in part, to reduced motility. Overall, these data suggest that metabolism of 1-BrP is mediated in part by CYP2E1, and activation of 1BrP via this enzyme may contribute to the male reproductive toxicity of this chemical.     

Algorithm of OMA for large-scale orthology inference

Background  

OMA is a project that aims to identify orthologs within publicly available, complete genomes. With 657 genomes analyzed to date, OMA is one of the largest projects of its kind.     

Altered profile of secondary metabolites in the root exudates of Arabidopsis ATP-binding cassette transporter mutants

Following recent indirect evidence suggesting a role for ATP-binding cassette (ABC) transporters in root exudation of phytochemicals, we identified 25 ABC transporter genes highly expressed in the root cells most likely to be involved in secretion processes. Of these 25 genes, we also selected six full-length ABC transporters and a half-size transporter for in-depth molecular and biochemical analyses. We compared the exuded root phytochemical profiles of these seven ABC transporter mutants to those of the wild type. There were three nonpolar phytochemicals missing in various ABC transporter mutants compared to the wild type when the samples were analyzed by high-performance liquid chromatography-mass spectrometry. These data suggest that more than one ABC transporter can be involved in the secretion of a given phytochemical and that a transporter can be involved in the secretion of more than one secondary metabolite. The primary and secondary metabolites present in the root exudates of the mutants were also analyzed by gas chromatography-mass spectrometry, which allowed for the identification of groups of compounds differentially found in some of the mutants compared to the wild type. For instance, the mutant Atpdr6 secreted a lower level of organic acids and Atmrp2 secreted a higher level of amino acids as compared to the wild type. We conclude that the release of phytochemicals by roots is partially controlled by ABC transporters.     

Metabolomics reveals novel pathways and differential mechanistic and elicitor-specific responses in phenylpropanoid and isoflavonoid biosynthesis in Medicago truncatula cell cultures

High-performance liquid chromatography coupled to ultraviolet photodiode array detection and ion-trap mass spectrometry was used to analyze the intra- and extracellular secondary product metabolome of Medicago truncatula cell suspension cultures responding to yeast elicitor (YE) or methyl jasmonate (MeJA). Data analysis revealed three phases of intracellular response to YE: a transient response in mainly (iso)flavonoid metabolites such as formononetin and biochanin-A that peaked at 12 to 18 h following elicitation and then declined; a sustained response through 48 h for compounds such as medicarpin and daidzin; and a lesser delayed and protracted response starting at 24 h postelicitation, e.g. genistein diglucoside. In contrast, most compounds excreted to the culture medium reached maximum levels at 6 to 12 h postelicitation and returned to basal levels by 24 h. The response to MeJA differed significantly from that to YE. Although both resulted in accumulation of the phytoalexin medicarpin, coordinated increases in isoflavonoid precursors were only observed for YE and not MeJA-treated cells. However, MeJA treatment resulted in a correlated decline in isoflavone glucosides, and did not induce the secretion of metabolites into the culture medium. Three novel methylated isoflavones, 7-hydroxy-6,4'-dimethoxyisoflavone (afrormosin), 6-hydroxy-7,4'-dimethoxyisoflavone (alfalone), and 5,7-dihydroxy-4',6-dimethoxy isoflavone (irisolidone), were induced by YE, and labeling studies indicated that the first two were derived from formononetin. Our results highlight the metabolic flexibility within the isoflavonoid pathway, suggest new pathways for complex isoflavonoid metabolism, and indicate differential mechanisms for medicarpin biosynthesis depending on the nature of elicitation.     

Hypertrophy and/or Hyperplasia: Dynamics of Adipose Tissue Growth

Adipose tissue grows by two mechanisms: hyperplasia (cell number increase) and hypertrophy (cell size increase). Genetics and diet affect the relative contributions of these two mechanisms to the growth of adipose tissue in obesity. In this study, the size distributions of epididymal adipose cells from two mouse strains, obesity-resistant FVB/N and obesity-prone C57BL/6, were measured after 2, 4, and 12 weeks under regular and high-fat feeding conditions. The total cell number in the epididymal fat pad was estimated from the fat pad mass and the normalized cell-size distribution. The cell number and volume-weighted mean cell size increase as a function of fat pad mass. To address adipose tissue growth precisely, we developed a mathematical model describing the evolution of the adipose cell-size distributions as a function of the increasing fat pad mass, instead of the increasing chronological time. Our model describes the recruitment of new adipose cells and their subsequent development in different strains, and with different diet regimens, with common mechanisms, but with diet- and genetics-dependent model parameters. Compared to the FVB/N strain, the C57BL/6 strain has greater recruitment of small adipose cells. Hyperplasia is enhanced by high-fat diet in a strain-dependent way, suggesting a synergistic interaction between genetics and diet. Moreover, high-fat feeding increases the rate of adipose cell size growth, independent of strain, reflecting the increase in calories requiring storage. Additionally, high-fat diet leads to a dramatic spreading of the size distribution of adipose cells in both strains; this implies an increase in size fluctuations of adipose cells through lipid turnover.     

Structural and functional analysis of the GABARAP interaction motif (GIM)

Through the canonical LC3 interaction motif (LIR), [W/F/Y]‐X₁‐X₂‐[I/L/V], protein complexes are recruited to autophagosomes to perform their functions as either autophagy adaptors or receptors. How these adaptors/receptors selectively interact with either LC3 or GABARAP families remains unclear. Herein, we determine the range of selectivity of 30 known core LIR motifs towards individual LC3s and GABARAPs. From these, we define a I nteraction 相似文献