Choline kinase activities in choline-sensitive and choline-resistant tobacco cells or calluses grown on high choline concentrations. Effects on phosphatidylcholine synthesis

Gawer, M.; Guern, N.; Chervin, D.; Mazliak, P.

doi:10.1016/0168-9452(91)90231-v

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…The modeled K m for the cytidylyltransferase of 80 nmol g Ϫ1 fresh weight corresponds to 3.3 mm (80 nmol/24 L ϭ 3.3 mm), which is within a factor of three of the measured K m for P-Cho of the castor bean enzyme (1.1 mm; Wang and Moore, 1989). The modeled K m for Cho kinase, 1.7 mm, is within the range reported for plants (0.03-2.5 mm; Setty and Krishnan, 1972;Bligny et al, 1989;Gawer et al, 1991). The modeled V max values for both enzymes also fall inside the limits known for plant tissues (e.g.…”

Section: Model Outputs and Their Implicationssupporting

confidence: 55%

Metabolic Modeling Identifies Key Constraints on an Engineered Glycine Betaine Synthesis Pathway in Tobacco

et al. 2000

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Previous work has shown that tobacco (Nicotiana tabacum) plants engineered to express spinach choline monooxygenase in the chloroplast accumulate very little glycine betaine (GlyBet) unless supplied with choline (Cho). We therefore used metabolic modeling in conjunction with [14 C]Cho labeling experiments and in vivo 31 P NMR analyses to define the constraints on GlyBet synthesis, and hence the processes likely to require further engineering. The [14 C]Cho doses used were large enough to markedly perturb Cho and phosphocholine pool sizes, which enabled development and testing of models with rates dynamically responsive to pool sizes, permitting estimation of the kinetic properties of Cho metabolism enzymes and transport systems in vivo. This revealed that import of Cho into the chloroplast is a major constraint on GlyBet synthesis, the import rate being approximately 100-fold lower than the rates of Cho phosphorylation and transport into the vacuole, with which import competes. Simulation studies suggested that, were the chloroplast transport limitation corrected, additional engineering interventions would still be needed to achieve levels of GlyBet as high as those in plants that accumulate GlyBet naturally. This study reveals the rigidity of the Cho metabolism network and illustrates how computer modeling can help guide rational metabolic engineering design. Daniel Koshland's recent commentary on "the era of pathway quantification" encapsulates the growing importance to basic biochemistry of mathematical tools for quantifying metabolic fluxes in vivo (1998). Moreover, advances in metabolic control theory and metabolic engineering experience show that we must quantify fluxes if we wish to understand metabolism well enough to manipulate it effectively (Fell,

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Section: Model Outputs and Their Implicationssupporting

confidence: 55%

Metabolic Modeling Identifies Key Constraints on an Engineered Glycine Betaine Synthesis Pathway in Tobacco

et al. 2000

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“…In contrast, in GlyBet-accumulating species such as spinach or beet, Cho import and oxidation by chloroplasts clearly compete effectively against Cho kinase and Cho transport into the vacuole (Hanson and Rhodes, 1983;Summers and Weretilnyk, 1993). There is no evidence that spinach Cho kinase has a markedly higher K m value than that in tobacco or other plants that lack GlyBet (Tanaka et al, 1966;Bligny et al, 1989;Gawer et al, 1991). From this it follows that the chloroplasts of species such as spinach and beet may have a high-affinity, high-activity Cho transporter that tobacco chloroplasts lack.…”

Section: And1mentioning

confidence: 84%

Choline Import into Chloroplasts Limits Glycine Betaine Synthesis in Tobacco: Analysis of Plants Engineered with a Chloroplastic or a Cytosolic Pathway

Nuccio

McNeil

Ziemak

et al. 2000

Metabolic Engineering

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“…However, since it has been reported that Cho, once inside plant cells, is rapidly converted into PCho (Bligny et al, 1989;Gout et al, 1990;Gawer et al, 1991), it is possible that a more efficient Cho uptake could lead to higher endogenous concentration of PCho in treated seedlings than when exogenous PCho is added to the media. To determine the inducer of the uORF30-dependent translational repression of XIPOTL1, analyses of relationships between the translational repression of the mORF and the endogenous levels of PCho and Cho in WT seedlings treated with different concentrations of Cho and PCho were carried out.…”

Section: Pcho Is Likely the Inducer Of The Uorf30-dependent Translatimentioning

confidence: 99%

“…It has been shown that exogenous Cho once inside the plant cell is rapidly converted into its phosphorylated form (Bligny et al, 1989;Gout et al, 1990;Gawer et al, 1991). Therefore, the current study tested whether PCho rather than Cho could be the direct mediator of the translational control by uORF30.…”

Section: Pcho Levels Regulate Uorf30-mediated Translational Repressiomentioning

confidence: 99%

Translational regulation of Arabidopsis XIPOTL1 is modulated by phosphocholine levels via the phylogenetically conserved upstream open reading frame 30

Alatorre‐Cobos¹,

Cruz‐Ramírez²,

Hayden

et al. 2012

Journal of Experimental Botany

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In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short-(6 h) and long-(2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

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Choline kinase activities in choline-sensitive and choline-resistant tobacco cells or calluses grown on high choline concentrations. Effects on phosphatidylcholine synthesis

Cited by 5 publications

References 28 publications

Metabolic Modeling Identifies Key Constraints on an Engineered Glycine Betaine Synthesis Pathway in Tobacco

Metabolic Modeling Identifies Key Constraints on an Engineered Glycine Betaine Synthesis Pathway in Tobacco

Choline Import into Chloroplasts Limits Glycine Betaine Synthesis in Tobacco: Analysis of Plants Engineered with a Chloroplastic or a Cytosolic Pathway

Translational regulation of Arabidopsis XIPOTL1 is modulated by phosphocholine levels via the phylogenetically conserved upstream open reading frame 30

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