The subcellular distribution and biosynthesis of castaprenols and plastoquinone in the leaves of Aesculus hippocastanum.
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ABSTRACT:
SUBMITTER: Wellburn AR
PROVIDER: S-EPMC1270558 | biostudies-other | 1967 Jul
REPOSITORIES: biostudies-other
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Project description:Aesculus L. (buckeye and horse chestnut) are woody plant species with important horticultural and medicinal values. Aesculus seeds are widely used as biomedicine and cosmetic ingredients due to their saponins. We report a chromosomal-scale genome of Aesculus wilsonii. Sequences amounting to a total of 579.01 Mb were assembled into 20 chromosomes. More than half of the genome (54.46%) were annotated as repetitive sequences, and 46,914 protein-coding genes were predicted. In addition to the widespread gamma event with core eudicots, a unique whole-genome duplication (WGD) event (17.69 Mya) occurred in Aesculus after buckeye differentiated from longan. Due to WGD events and tandem duplications, the related synthetic genes of triterpene saponins unique to Aesculus increased significantly. Combined with transcriptome characterization, the study preliminarily resolved the biosynthetic pathway of triterpenoid saponins like aescin in A. wilsonii genome. Analyses of the resequencing of 104 buckeye accessions revealed clear relationship between the geographic distribution and genetic differentiation of buckeye trees in China. We found that the buckeye species found in southern Shaanxi is A. wilsonii rather than A. chinensis. Population dynamics analysis further suggests that the population size and evolution of existing buckeye species have been influenced by climate fluctuations during the Pleistocene and recent domestication events. The genome of A. wilsonii and population genomics of Aesculus provide a resource for future research on Hippocastanaceae. These findings will contribute to the utilization and diversity protection of Aesculus.
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Project description:A polyprenol complex of Aspergillus niger was shown, by using spectrometric methods, to consist of a family of exo-methylene-hexahydroprenols that contain between 18 and 24 isoprene residues per molecule. Each prenol contains two trans residues, three saturated residues (alpha, omega and psi) and an exo-methylene substituent on the carbon atom beta to the isopropyl group in each omega-residue. The ubiquinone complex consisted of 90% ubiquinone-9, 9% ubiquinone-8 and 1% ubiquinone-10. The amount of polyprenol complex present reached a maximum of 1.7mg/culture bottle after 9-10 days of growth, coincident with the maximum weight of mycelium. The amount of ergosterol (10mg/culture bottle) and ubiquinone (1mg/culture bottle) reached a peak at 8 days. By the 13th day of growth the yield of ergosterol had fallen by 20% and that of ubiquinone by 85%. A study of the incorporation of [2-(14)C]mevalonate over different time-intervals confirmed that there was a slow turnover of prenol, a more rapid turnover of ergosterol and a very rapid turnover of ubiquinone. At any one time each member of the prenol complex had essentially the same specific radioactivity as other members of the complex. A similar conclusion was made about the ubiquinone mixture. Just over half of the polyprenol present was esterified to fatty acids. Subcellular fractionation studies indicated that the unesterified prenol is associated primarily with a mitochondrial fraction, whereas the ester is more widely distributed.
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Project description:Homogentisate solanesyl transferase (HST) catalyzes the prenylation and decarboxylation of homogentisate to form 2-methyl-6-solanesyl-1,4-benzoquinol, the first intermediate in plastoquinone-9 biosynthesis. In vitro, HST from Spinacia oleracea L., Arabidopsis thaliana, and Chlamydomonas reinhardtii were all found to use not only solanesyl diphosphate but also short chain prenyl diphosphates of 10-20 carbon atoms as prenyl donors. Surprisingly, with these donors, prenyl transfer was largely decoupled from decarboxylation, and thus the major products were 6-prenyl-1,4-benzoquinol-2-methylcarboxylates rather than the expected 2-methyl-6-prenyl-1,4-benzoquinols. The 6-prenyl-1,4-benzoquinol-2-methylcarboxylates were not substrates for HST-catalyzed decarboxylation, and the enzyme kinetics associated with forming these products appeared quite distinct from those for 2-methyl-6-prenyl-1,4-benzoquinol formation in respect of catalytic rate, substrate K(m) value, and the pattern of inhibition by haloxydine, a molecule that appeared to act as a dead end mimic of homogentisate. These observations were reconciled into a simple model for the HST mechanism. Here, prenyl diphosphate binds to HST to form at least two alternative complexes that go on to react differently with homogentisate and prenylate it either with or without it first being decarboxylated. It is supposed that solanesyl diphosphate binds tightly and preferentially in the mode that compels prenylation with decarboxylation.
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Project description:Plastoquinone-9 is known as a photosynthetic electron carrier to which has also been attributed a role in the regulation of gene expression and enzyme activities via its redox state. Here, we show that it acts also as an antioxidant in plant leaves, playing a central photoprotective role. When Arabidopsis plants were suddenly exposed to excess light energy, a rapid consumption of plastoquinone-9 occurred, followed by a progressive increase in concentration during the acclimation phase. By overexpressing the plastoquinone-9 biosynthesis gene SPS1 (solanesyl diphosphate synthase 1) in Arabidopsis, we succeeded in generating plants that specifically accumulate plastoquinone-9 and its derivative plastochromanol-8. The SPS1-overexpressing lines were much more resistant to photooxidative stress than the wild type, showing marked decreases in leaf bleaching, lipid peroxidation and PSII photoinhibition under excess light. Comparison of the SPS1 overexpressors with other prenyl quinone mutants indicated that the enhanced phototolerance of the former plants is directly related to their increased capacities for plastoquinone-9 biosynthesis.
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Project description:HeLa cells were fractioned in nucleus and cytoplasm to investigate the subcellular distribution of lncRNAs. Two-condition experiment, nuclear fraction vs. cytoplasmatic fraction from HeLa cells. Biological replicates: 2 with dye-swap
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Project description:Cyanobacteria can utilize CO2 or even N2 to produce a variety of high value-added products efficiently. Plastoquinone (PQ) is an important electron carrier in both of the photosynthetic and respiratory electron transport chain. Although the content of PQ, as well as their redox state, have an important effect on physiology and metabolism, there are relatively few studies on the synthesis of PQ and its related metabolic regulation mechanism in photosynthetic microorganisms. In this study, the strategies of overexpression of Geranyl diphosphate: 4-hydroxybenzoate geranyltransferase (lepgt) and addition of 4-hydroxybenzoate (4-HB) as the quinone ring precursor were adopted to regulate the biosynthesis of PQ in Synechocystis PCC 6803. Combined with the analysis the photosystem activity, respiration rate and metabolic components, we found the changes of intracellular PQ reprogrammed the metabolism of Synechocystis PCC 6803. The results showed that the overexpression of lepgt reduced PQ content dramatically, by 22.18%. Interestingly, both of the photosynthesis and respiration rate were enhanced. In addition, the intracellular lipid and protein contents were significantly increased. Whereas, the addition of low concentrations of 4-HB enhanced the biosynthesis of PQ, and the intracellular PQ contents were increased by 14.76%-70.86% in different conditions. Addition of 4-HB can regulate the photosystem efficiency and respiration and reprogram the metabolism of Synechocystis PCC 6803 efficiently. In a word, regulating the PQ biosynthesis provided a novel idea for promoting the reprogramming the physiology and metabolism of Synechocystis.
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Project description:HeLa cells were fractioned in nucleus and cytoplasm to investigate the subcellular distribution of lncRNAs.
2015-06-30 | GSE62985 | GEO
Project description:Cholesterol synthesis is a complex, coordinated process involving a series of enzymes. As of today, our understanding of subcellular localization of cholesterol biosynthesis enzymes is far from complete. Considering the complexity and intricacies of this pathway and the importance of functions of DHCR7, DHCR24 and EBP enzymes for human health, we undertook a study to determine their subcellular localization and co-localization. Using expression constructs and antibody staining in cell cultures and transgenic mice, we found that all three enzymes are expressed in ER and nuclear envelope. However, their co-localization was considerably different across the cellular compartments. Furthermore, we observed that in the absence of DHCR7 protein, DHCR24 shows a compensatory upregulation in a Dhcr7-/- transgenic mouse model. The overall findings suggest that the sterol biosynthesis enzymes might not always work in a same functional complex, but that they potentially have different, multifunctional roles that go beyond the sterol biosynthesis pathway. Furthermore, the newly uncovered compensatory mechanism between DHCR7 and DHCR24 could be of importance for designing medications that would improve cholesterol production in patients with desmosterolosis and Smith-Lemli-Opitz syndrome.
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Project description:1. By using dl-[ring-(14)C]phenylalanine, dl-[beta-(14)C]phenylalanine, dl-[alpha-(14)C]-tyrosine and dl-[beta-(14)C]tyrosine it was shown that in maize shoots (Zea mays) the nucleus and one nuclear methyl group of each of the following compounds, plastoquinone, gamma-tocopherol (aromatic nucleus) and alpha-tocopherolquinone, are formed from the nuclear carbon atoms and beta-carbon atom respectively of either exogenous phenylalanine or exogenous tyrosine. With ubiquinone only the aromatic ring of the amino acid is used in the synthesis of the quinone nucleus. Chemical degradation of plastoquinone and gamma-tocopherol molecules labelled from l-[U-(14)C]tyrosine established that a C(6)-C(1) unit directly derived from the amino acid is involved in the synthesis of these compounds. Radioactivity from [beta-(14)C]cinnamic acid is not incorporated into plastoquinone, tocopherols or tocopherolquinones, demonstrating that the C(6)-C(1) unit is not formed from any of the C(6)-C(1) phenolic acids associated with the metabolism of this compound. 2. The incorporation of radioactivity from l-[U-(14)C]tyrosine, dl-[beta-(14)C]tyrosine and dl-[U-(14)C]phenylalanine into bean shoots (Phaseolus vulgaris) and dl-[beta-(14)C]tyrosine and l-[Me-(14)C]methionine into ivy leaves (Hedera helix) was also investigated. Similar results were obtained to those reported for maize, except that in beans phenylalanine is only used for ubiquinone biosynthesis. This is attributed to the absence of phenylalanine hydroxylase from these tissues. In ivy leaves it is found that the beta-carbon atom of tyrosine gives rise to the 8-methyl group of delta-tocopherol, and it is suggested that for all other compounds examined it will give rise to the nuclear methyl group meta to the polyprenyl unit. 3. Preliminary investigations with the alga Euglena gracilis showed that in this organism ring-opening of tyrosine occurs to such an extent that the incorporation data from radiochemical experiments are meaningless. 4. The above results, coupled with previous observations, are interpreted as showing that in higher plants the nucleus of ubiquinone can be formed from either phenylalanine or tyrosine by a pathway involving as intermediates p-coumaric acid and p-hydroxybenzoic acid. Plastoquinone, tocopherols and alpha-tocopherolquinone are formed from p-hydroxyphenylpyruvate by a pathway in which the aromatic ring and C-3 of the side chain give rise respectively to the nucleus and to one nuclear methyl group. 5. Dilution experiments provided evidence that in maize shoots p-hydroxyphenylpyruvic acid and homogentisic acid (produced from p-hydroxyphenylpyruvic acid) are involved in plastoquinone biosynthesis, and presumably the biosynthesis of related compounds: however, other possible intermediates in the conversion including toluquinol (the aglycone of the proposed key intermediate) showed no dilution effects. Further, radioactivity from [Me-(14)C]toluquinol is not incorporated into any of the compounds examined. 6. Dilution experiments with 3,4-dihydroxybenzaldehyde and radioactive-labelling experiments with 3,4-dihydroxy[U-(14)C]benzoic acid demonstrated that these compounds are not involved in the biosynthesis of either ubiquinone or phylloquinone in maize shoots. 7. Evidence is also presented to show that in maize shoots ring-opening of the aromatic amino acids takes place. The suggestion is offered that this may take place via homogentisic acid, as in animals and some micro-organisms.
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