Growth and Secondary Metabolite Production by Hairy Roots of Tagetes Patula in Aqueous Two-Phase Systems

Hairy roots of Tagetes patula have been grown in aqueous two-phase systems. After selecting suitable polymers from single-phase experiments (in which salt phases were unable to support growth in the desired concentrations) several two-phase systems were tested for their influence on cell growth and thiophene production. Cell growth occurred in all aqueous two-phase systems, but the highest growth rate was achieved in normal medium. There was no difference in thiophene production between medium and aqueous two-phase systems. The partition of thiophenes favoured slightly the more hydrophobic top phase in most cases, while the cells were confined to the bottom phase. One aqueous two-phase system (15% polyethyleneglycol 10,000 and 15% Reppal PES 200) was tested in a stirred tank reactor with normal medium as a control. The growth rate in medium was higher than in the aqueous two-phase system, while the thiophene production per unit cell weight was in the same range for both systems. The excretion of thiophenes in the reactor with the aqueous two-phase system was about ten times as high as in the control reactor. The amount excreted was however still not more than 3% of the total production.     

Foliage acceptability to browsing ruminants in relation to seasonal changes in the leaf chemistry of woody plants in a South African savanna

Summary We investigated seasonal changes in food selection by hand-reared kudus and impalas in savanna vegetation in northern Transvaal, South Africa. The acceptability of the leaves of woody plants to these animals was compared with leaf concentrations of nutrients, fibre components and old leaf phenophases. No consistently significant correlation was found between acceptability and any single chemical factor. Based on an a priori palatability classification, discriminant function analysis separated relatively palatable species from unpalatable species in terms of a linear combination of protein and condensed tannin concentrations. The high acceptability of certain otherwise unpalatable species during the new leaf phenophase was related to elevation of protein levels relative to condensed tannin contents. Species were added to the diet during the dry season approximately in the order of their relative protein-condensed tannin difference.     

Vitamin D and related compounds as plant growth substances

Vitamin D and related compounds (hydroxylated derivatives and glycosides) occur naturally in certain plants. The metabolism of vitamin D₃ in Solanum malacoxylon Sendtn. is similar in certain respects to that in animal systems. There is also evidence that vitamin D₃, plays a role in processes regulated by Ca²⁺ in plants. Vitamin D₃ possesses plant growth substance activities and in particular enhances adventitious root formation.     

P-31 Nuclear Magnetic Resonance Analysis of Brain: II. Effects of Oxygen Deprivation on Isolated Perfused and Nonperfused Rat Brain

Phosphatic metabolite (perchloric acid extractable) concentrations of cerebral tissues were analyzed by phosphorus-31 nuclear magnetic resonance (P-31 NMR) spectroscopy following external perfusion of the isolated rat brain (30 min or 60 min) under the following conditions: (a) constant perfusion pressure with either fluorocarbon- or erythrocyte-based medium, and (b) constant perfusate flow rate (3 ml/min) with the erythrocyte-based medium. Metabolite concentrations of control perfused brains were compared with those in nonperfused controls to provide a basis for detecting any qualitative or quantitative changes in cerebral metabolite composition. Metabolic responses of perfused brains to ischemia (incomplete ischemia, 83% reduction in flow for 10 min; transient complete ischemia for 1.5 or 2 min) were evaluated immediately after the ischemic episode and at selected time points during reperfusion (3 and 15 min). Alterations in cerebral metabolite levels induced by hypoxia were analyzed using a nonperfused rat brain model. Irrespective of the perfusion method employed, the phosphatic metabolites of control perfused rat brains were identical quantitatively to those of the nonperfused controls. Cerebral ischemia resulted in significantly increased levels of ADP, AMP + IMP, Pi, fructose 1,6-diphosphate, and glycerol 3-phosphate (global ischemia only), whereas ATP and phosphocreatine (PCr) levels declined significantly. The magnitude of these changes varied with the severity of the ischemia; however, following 15 min of control reperfusion metabolite levels had reverted to preischemic values. Significant perturbations in tissue phosphoethanolamine (3.84 delta resonance) content were evident at various time points during ischemia and postischemic recovery, which varied according to the perfusion conditions. In contrast to the changes observed in response to ischemia, hypoxia affected only cerebral high-energy phosphate levels. ATP and PCr levels were reduced, while a concomitant, essentially equimolar, increase in Pi and ADP was observed. The present studies indicate that in terms of phosphatic metabolites, the control equilibrated isolated perfused rat brain is quantitatively and qualitatively indistinguishable from the nonperfused rat brain in vivo regardless of the perfusion conditions (constant flow versus constant pressure). The metabolic responses to ischemia and hypoxia, as measured by P-31 NMR, were consistent with the pattern of changes reported elsewhere. Overall, P-31 NMR spectroscopic evaluation of the intact rat brain provides a potential experimental context for dynamic measures of cerebral metabolism under exogenously controlled conditions. Th     

The toxic effects in rats of some synthanecine carbamate and phosphate esters analogous to hepatotoxic pyrrolizidine alkaloids

Five synthetic compounds analogous to pyrrolizidine alkaloids have been tested for toxicity in rats. These were the bis-N-ethylcarbamate esters of synthanecines A, B, C and D (Compounds I–IV) and the bis-diethylphosphate ester (V) of synthanecine A. The amino alcohol moiety in each of these had a single 5-membered heterocyclic ring in place of the pyrrolizidine amino alcohol (necine) moiety of natural pyrrolizidine alkaloids.The toxicity of these compounds differed considerably. The synthanecine A carbamate (I) was the most toxic, male and female rats being similarly susceptible. Like many hepatotoxic pyrrolizidine alkaloids, a single dose of compound I caused acute centrilobular necrosis of the liver, chronic hepatotoxicity involving the development of persistent giant hepatocytes, and chronic lung injury. Compound III had similar actions but was less toxic. The synthanecine D carbamate (IV) caused acute liver necrosis but no chronic hepatotoxicity, whereas the synthanecine A phosphate (V) had the opposite effect, with only chronic hepatotoxicity.The different toxic effects were related to the structure and metabolism of the compounds. Doses of compounds I, III and IV associated with a similar degree of acute hepatotoxicity led to similar levels of pyrrolic metabolites in the liver. Compound II, which was not hepatotoxic, gave very little liver pyrrole. The liver level of pyrrolic metabolite from the phosphate ester (V) decreased more rapidly than that from (I), and was not associated with acute toxicity.Antimitotic activity, indicated by the appearance of bizarre giant cells, was shown by compounds capable of forming pyrrolic metabolites which were bifunctional alkylating agents, but not by compound IV, which could only form a monofunctional alkylating agent. Pretreatment with phenobarbitone lowered the susceptibility of rats to compound I and greatly increased the liver level of pyrrolic metabolites associated with acute hepatotoxicity. Some rats given compounds I and III had kidney lesions primarily involving the glomerulus. The results confirm that toxic effects characteristic of many natural pyrrolizidine alkaloids can be reproduced using simplified synthetic analogues, and that such toxicity is associated with pyrrolic metabolites.     

Bottlenecks in carotenoid biosynthesis and accumulation in rice endosperm are influenced by the precursor–product balance

The profile of secondary metabolites in plants reflects the balance of biosynthesis, degradation and storage, including the availability of precursors and products that affect the metabolic equilibrium. We investigated the impact of the precursor–product balance on the carotenoid pathway in the endosperm of intact rice plants because this tissue does not normally accumulate carotenoids, allowing us to control each component of the pathway. We generated transgenic plants expressing the maize phytoene synthase gene (ZmPSY1) and the bacterial phytoene desaturase gene (PaCRTI), which are sufficient to produce β‐carotene in the presence of endogenous lycopene β‐cyclase. We combined this mini‐pathway with the Arabidopsis thaliana genes AtDXS (encoding 1‐deoxy‐D‐xylulose 5‐phosphate synthase, which supplies metabolic precursors) or AtOR (the ORANGE gene, which promotes the formation of a metabolic sink). Analysis of the resulting transgenic plants suggested that the supply of isoprenoid precursors from the MEP pathway is one of the key factors limiting carotenoid accumulation in the endosperm and that the overexpression of AtOR increased the accumulation of carotenoids in part by up‐regulating a series of endogenous carotenogenic genes. The identification of metabolic bottlenecks in the pathway will help to refine strategies for the creation of engineered plants with specific carotenoid profiles.     

Growth metabolism of wheat under drought stress at the jointing-booting stage

AimsThe aim of this study was to investigate the effects of drought stress on primary, secondary metabolites and metabolic pathways in the leaves of wheat, these parameters were evaluated to determine the physiological adaptive mechanisms by which wheat tolerates drought stress at the jointing-booting stage.MethodsA pot experiment was carried out in rain-proof shelter. The relative growth rate, photosynthetic characteristics and metabolism seedlings exposed to stresses lasting 12 days at jointing-booting stage were measured.Important findings The results displayed that the photosynthesis decreased under drought stress, causing the decreases of relative growth rate and dry matter mass. Profiles of 64 key metabolites produced by wheat including organic acids, amino acids, carbohydrates, purine, etc. were examined, 29 of them were changed significantly under drought stress. Principal component analysis (PCA) showed that 64% variations can be explained by the two principal components. One-way ANOVA analysis results revealed that long term drought stress decreased malic acid, citric acid and aconitic acid significantly, indicating inhibited tricarboxylic acid cycle. We further found that prolonged drought stress led to accumulation of progressive amino acids (proline, serine, valine) and carbohydrates (myo-inositol, fructose, clucose) in wheat leaves and depletion of transamination products (asparagine, glutamine, γ-aminobutyric acid). These results imply wheat may enhance its drought tolerance mainly by increasing amino acid biosynthesis and glycolysis under water-deficit conditions. Our findings suggest that drought condition altered metabolic networks including transamination, the tricarboxylic cycle, gluconeogenesis/glycolysis, glutamate-mediated proline biosynthesis, and the metabolisms of choline, pyrimidine and purine. This study provides new insights into the metabolic adaptation of wheat to drought stress and important information for developing drought-tolerant wheat cultivars.     

光质对紫背天葵生长、次生代谢和抗氧化胁迫的影响

以紫背天葵为供试材料,采用LED灯精量调控光质和光强,研究相同光照强度(350±5 μmol·m^-2·s^-1)下,白光(W)、红光(R)、蓝光(B)、黄光(Y)、红蓝混合光(RB)、红蓝黄混合光(RBY)对紫背天葵生长、次生代谢和氧化胁迫抗性的影响.结果表明:与白光(W)相比,红光(R)能够显著促进紫背天葵植株的生长以及干物质和可溶性糖含量的积累;而蓝光(B)则抑制紫背天葵的生长;叶绿素含量在有色光处理下均显著降低;虽然红蓝黄混合光(RBY)未能显著提升紫背天葵的干物质含量,但总酚、类黄酮和花青素含量显著提升,这些还原态物质的积累有利于提高紫背天葵的抗氧化能力,在增强自身抗逆性的同时提升营养价值.本研究为光质调控紫背天葵的多样化生产提供了理论依据.