Atypical TCA cycle and replenishment in a non-photosynthetic fully habituated sugarbeet callus overproducing polyamines

In a fully habituated (hormone independent) white sugarbeet callus overconsuming oxygen, and overproducing polyamines from deviated nitrogen metabolism through glutamate, the question of the synthesis of the tricarboxylic acid (TCA) cycle intermediates (between (α-cetoglutarate and citrate) was raised. The present paper first completes earlier results indicating an anaplerotic pathway involving non-photosynthetic CO2-fixation with higher activities of phosphoenolpyruvate carboxylase and malate dehydrogenase. Additional original results indicate a second TCA replenishing pathway through a γ-aminobutyric acid (GABA)-shunt from polyamines to succinate, with higher activities of the intermediary enzymes of the habituated callus than in the normal counterpart. Such a GABA-shunt shown to occur frequently in tissues under stress is well in agreement with the formerly proposed permanent stress of the habituated callus. A tentative scheme of this atypical TCA cycle, which also illustrates the interrelationships between the deviated sugar and nitrogen metabolisms in this callus, is presented

Erythromycin as a tool to investigate the tetrapyrrole biosynthetic pathways in habituated and normal sugarbeet calli

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Wood formation in in vitro propagated walnut shoots in relation with root formation and development

Lignification and xylem cell multiplication for wood formation were examined in in vitro propagated walnut shoot cuttings after transfer on an auxin-containing rooting medium for one week and subsequently during root development in vermiculite in the absence of growth regulators. Lignification in the shoot stems started immediately after the exogenous auxin treatment which implied changes in peroxidase activity and in free IAA levels. Sustained lignification required the completion of the following rooting phases. The lignin was exclusively located in xylem cells, the number of which increased with the number of developing roots. The mutual interactions between the aerial parts of the plants and their roots are discussed

Erythromycin as a tool to investigate the tetrapyrrole biosynthetic pathways in habituated and normal sugarbeet calli

peer reviewedErythromycin (ERT) has been shown to reduce the 5-aminolevulinic acid (ALA) synthesizing capacity of a normal (N) chlorophyllous sugarbeet callus, grown under light, in contrast to a habituated achlorophyllous nonorganogenic (HNO) callus of the same species. Similar effects were obtained on total hemes and on catalase which is a hemoprotein used as marker. The effect of ERT, which is an inhibitor of plastid differentiation and of chlorophyll synthesis, was reversed in the N callus by a supply of glycine and succinate. The compounds are the precursors of ALA synthesized through 5-aminolevulinic acid synthase (ALAS) which is implied in the Shemin pathway. The involvement of ALAS appeared to be favoured when plastids were undifferentiated (HNO callus) or when plastids were inefficient (N callus under darkness or under light after ERT treatment)

Darkness improves growth and delays necrosis in a nonchloropyllous habituated sugarbeet callus: Biochemical changes

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Disturbed sugar metabolism in a fully habituated nonorganogenic callus of Beta vulgaris (L.)

peer reviewedHabituated (H) nonorganogenic sugarbeet callus was found to exhibit a disturbed sugar metabolism. In contrast to cells from normal (N) callus, H cells accumulate glucose and fructose and show an abnormal high fructose/glucose ratio. Moreover, H cells which have decreased wall components, display lower glycolytic enzyme activities (hexose phosphate isomerase and phosphofructokinase) which is compensated by higher activities of the enzymes of the hexose monophosphate pathway (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase). The disturbed sugar metabolism of the H callus is discussed in relation to a deficiency in H2O2 detoxifying systems. © 1993 Kluwer Academic Publishers

Darkness improves growth and delays necrosis in a nonchlorophyllous habituated sugarbeet callus: Biochemical changes

The transfer of light-cultured green normal (N) and white habituated (HNO) sugarbeet callus to darkness reduced the growth of N callus and improved growth and delayed necrosis in the HNO callus. The decrease of dry matter of N callus under darkness was accompanied by a reduced content of carotenoids and by decreased CO2 fixation, which was compensated by an increased dependency on externally supplied sucrose. The levels of some organic nitrogen compounds such as glutamate, proline, and free polyamines were not affected by transfer to darkness of N or HNO callus. Darkness decreased ethylene emissions in both callus types. In the HNO callus, the sucrose growth dependency and the CO2 fixation were unaffected by darkness. Chlorophylls were absent both in light and darkness, whereas some carotenoids were accumulated in the HNO callus only in dark conditions. In another connection, a significant increase of peroxidase activity, which did not occur in the N callus, was induced by darkness in the HNO callus. A decreased content of thio-barbituric acid (TBA)-reactive substances was measured in the HNO callus transferred to darkness, whereas an increase was noticed in the N callus placed in the same conditions. These metabolic changes and the reduction of cellular damage in darkness revealed light-induced stress reactions leading to necrosis and to reduced growth of HNO callus. It appeared that darkness allowed the HNO callus to avoid the photooxidation stress. Therefore, the favorable effect of darkness on HNO growth might be explained by the suppression of photooxidative damage due to the absence of carotenoids. The higher peroxidase activity in the HNO callus maintained in darkness raised the problem of heme synthesis in this heterotrophic callus. © 1995 Society for In Vitro Biology

Peroxidase isoenzymes in normal and habituated calli of sugar beet during transfer from light to darkness

peer reviewedHabituated sugar beet calli have been characterized as having a deficiency in some tetrapyrrole containing compounds. However, peroxidases might be dissociated from the other tetrapyrrole containing compounds. When light-cultured normal and habituated calli were transferred to darkness their peroxidase activity reduced and increased, respectively, indicating that habituation could not strictly be characterized by a deficiency in peroxidase content but rather by a different regulation of its activity. This regulation could be mediated through soluble effectors which act as potential peroxidase inhibitors and/or by a differential expression of the peroxidase isoenzyme patterns which were present in these tissues in both light and darkness. The different peroxidase activity and the nature of acidic and basic isoenzymes in normal and habituated tissues could explain the different features of both types of cultures

Environmental impact assessment of local decoupled multi-loop aquaponics in an urban context

Fresh vegetables available on Northern European markets usually originate from a high number of sources. Environmental impacts for these goods typically arise from the resources used in production and the long-distance transport in air-conditioned trucks. As such, environmental impacts are mainly attributed to direct energy consumption, water use and nutrient supply. The aim of this paper was therefore to investigate and evaluate possible solutions to reduce the environmental impacts of vegetables available on urban markets in Northern Europe. We hypothesise that for the production of lettuce and tomatoes in Northern Europe, a 4-step solution, i.e. 1) local production, 2) climate-controlled efficient greenhouses, 3) decoupled aquaponics, and 4) combined building architecture with waste heat and green waste reuse, will enable a low environmental impact. We defined the metropole Berlin as case example, and used simulation results from a proven greenhouse simulator as input to a comparing life cycle assessment of fresh lettuce and tomato. The assessment included a list of 12 midpoint environmental impact categories, e.g. global warming potential with 100 year horizon (GWP100; kg CO2 eq.), depletion of fossil fuel reserves (FRS; kg oil eq.), and water use (WCO; m3 water). Most impact categories decreased systematically when increasing the complexity of the local vegetable production. Compared to the mix of vegetables from different locations available on the market, the complete 4-step solution reduced WCO from water consumption to water saving: i.e. from 14.2 L or 3.3 L to −10.1 L or −0.21 L per package of 500 g tomatoes or 150 g lettuce, respectively. GWP100 and FRS were below the values of the available market mix, e.g. GWP100 decreased with 8.7% in tomatoes and 49.9% in lettuce. In conclusion, with the right set-up, local vegetable productions in urban regions can surpass the imported mix on environmental performance in Northern Europe.</p

Cancer végétal in vitro : aspects morphogénétiques et biochimiques

National audienc