Normal Growth of Transgenic Tobacco Plants in the Absence of Cytosolic Pyruvate Kinase

Gottlob-McHugh, Sylvia G.; Sangwan, Rajender S.; Blakeley, Stephen D.; Vanlerberghe, Greg C.; Ko, Kenton; Turpin, David H.; Plaxton, William C.; Miki, Brian; Dennis, David T.

doi:10.1104/pp.100.2.820

Cited by 54 publications

(23 citation statements)

References 32 publications

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“…At the same time, increased PEP and pyruvate levels were reported for the mutant, which is consistent with the idea of swelling of PEP levels in response to a reduction in PKp (Andre et al, 2007). Similar to PKp mutations, in PKc-deficient tobacco (Nicotiana tabacum) plants, the level of PEP in leaves was found to be significantly increased as compared with the wild type (Gottlob-McHugh et al, 1992).…”

Section: Control Of Carbon Partitioning Between Lipid and Starchsupporting

confidence: 73%

Quantitative Multilevel Analysis of Central Metabolism in Developing Oilseeds of Oilseed Rape during in Vitro Culture

et al. 2015

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Seeds provide the basis for many food, feed, and fuel products. Continued increases in seed yield, composition, and quality require an improved understanding of how the developing seed converts carbon and nitrogen supplies into storage. Current knowledge of this process is often based on the premise that transcriptional regulation directly translates via enzyme concentration into flux. In an attempt to highlight metabolic control, we explore genotypic differences in carbon partitioning for in vitro cultured developing embryos of oilseed rape (Brassica napus). We determined biomass composition as well as 79 net fluxes, the levels of 77 metabolites, and 26 enzyme activities with specific focus on central metabolism in nine selected germplasm accessions. Overall, we observed a tradeoff between the biomass component fractions of lipid and starch. With increasing lipid content over the spectrum of genotypes, plastidic fatty acid synthesis and glycolytic flux increased concomitantly, while glycolytic intermediates decreased. The lipid/starch tradeoff was not reflected at the proteome level, pointing to the significance of (posttranslational) metabolic control. Enzyme activity/flux and metabolite/flux correlations suggest that plastidic pyruvate kinase exerts flux control and that the lipid/starch tradeoff is most likely mediated by allosteric feedback regulation of phosphofructokinase and ADP-glucose pyrophosphorylase. Quantitative data were also used to calculate in vivo mass action ratios, reaction equilibria, and metabolite turnover times. Compounds like cyclic 39,59-AMP and sucrose-6-phosphate were identified to potentially be involved in so far unknown mechanisms of metabolic control. This study provides a rich source of quantitative data for those studying central metabolism.Seeds develop by absorbing nutrients from their mother plant and using these to synthesize a combination of starch, protein, and lipid. The size and number of seeds that finally develop determine the crop's yield, while their composition determines the end-use quality of the crop. The conversion of nutrients into storage products involves a complex network of metabolic reactions, many of which are subject to transcriptional, translational, and posttranslational regulation. Attempting to engineer seed composition clearly requires a firm understanding of these regulatory networks.The seed's central metabolism differs markedly from those of both a photosynthesizing leaf and a root. In most species, the immature seed is green for a period during its development, so during this phase it is regarded as being photoheterotrophic. A further level of complexity arises as a result of spatial heterogeneity within the seed (Rolletschek et al., 2011; Borisjuk et al.,

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Section: Control Of Carbon Partitioning Between Lipid and Starchsupporting

confidence: 73%

Quantitative Multilevel Analysis of Central Metabolism in Developing Oilseeds of Oilseed Rape during in Vitro Culture

et al. 2015

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“…A previous study demonstrated that transgenic tobacco plants lacking the expression of cytosolic pyruvate kinase showed basically normal growth (Gottlob-McHugh et al, 1992). However, in a later report, inhibition of root growth and a decrease in the export of fixed carbon from the leaves to other organs were observed when these transgenic tobacco plants were cultivated under low light intensities (Knowles et al, 1998).…”

Section: Discussionmentioning

confidence: 95%

Phosphoenolpyruvate Carboxylase in Arabidopsis Leaves Plays a Crucial Role in Carbon and Nitrogen Metabolism

et al. 2015

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Phosphoenolpyruvate carboxylase (PEPC) is a crucial enzyme that catalyzes an irreversible primary metabolic reaction in plants. Previous studies have used transgenic plants expressing ectopic PEPC forms with diminished feedback inhibition to examine the role of PEPC in carbon and nitrogen metabolism. To date, the in vivo role of PEPC in carbon and nitrogen metabolism has not been analyzed in plants. In this study, we examined the role of PEPC in plants, demonstrating that PPC1 and PPC2 were highly expressed genes encoding PEPC in Arabidopsis (Arabidopsis thaliana) leaves and that PPC1 and PPC2 accounted for approximately 93% of total PEPC activity in the leaves. A double mutant, ppc1/ppc2, was constructed that exhibited a severe growth-arrest phenotype. The ppc1/ppc2 mutant accumulated more starch and sucrose than wild-type plants when seedlings were grown under normal conditions. Physiological and metabolic analysis revealed that decreased PEPC activity in the ppc1/ppc2 mutant greatly reduced the synthesis of malate and citrate and severely suppressed ammonium assimilation. Furthermore, nitrate levels in the ppc1/ppc2 mutant were significantly lower than those in wild-type plants due to the suppression of ammonium assimilation. Interestingly, starch and sucrose accumulation could be prevented and nitrate levels could be maintained by supplying the ppc1/ppc2 mutant with exogenous malate and glutamate, suggesting that low nitrogen status resulted in the alteration of carbon metabolism and prompted the accumulation of starch and sucrose in the ppc1/ppc2 mutant. Our results demonstrate that PEPC in leaves plays a crucial role in modulating the balance of carbon and nitrogen metabolism in Arabidopsis.

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“…Plant Number cosuppression of beta-I, 3-glucanase genes (de Carvalho et al 1992), pyruvate kinase genes (Gottlob-McHugh et al 1992), nitrate reductase genes (Dorlhac de Borne et al 1994), and acetohydroxyacid synthase (Brandle et al 1995) genes.…”

Section: Instability Of Transgene Expressionmentioning

confidence: 99%

Transgenic Tobacco: Gene Expression and Applications

Miki

Mcttugh

Labbé

et al. 1999

Transgenic Medicinal Plants

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Normal Growth of Transgenic Tobacco Plants in the Absence of Cytosolic Pyruvate Kinase

Cited by 54 publications

References 32 publications

Quantitative Multilevel Analysis of Central Metabolism in Developing Oilseeds of Oilseed Rape during in Vitro Culture

Quantitative Multilevel Analysis of Central Metabolism in Developing Oilseeds of Oilseed Rape during in Vitro Culture

Phosphoenolpyruvate Carboxylase in Arabidopsis Leaves Plays a Crucial Role in Carbon and Nitrogen Metabolism

Transgenic Tobacco: Gene Expression and Applications

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