Transgenic potato plants with strongly decreased expression of pyrophosphate:fructose-6-phosphate phosphotransferase show no visible phenotype and only minor changes in metabolic fluxes in their tubers

Hajirezaei, Mohammad; Sonnewald, Uwe; Viola, Roberto; Carlisle, S M; Dennis, David T.; Stitt, Mark

doi:10.1007/bf00198688

Cited by 100 publications

(131 citation statements)

References 60 publications

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“…The different pools of 3-P-glycerate, cytosolic and plastidial, may change independently as they have been shown to do in leaves (Gerhardt et al, 1987). This could explain why correlations between 3-P-glycerate and starch synthesis have only been shown in some cases (Hajirezaei et al, 1994;Geigenberger et al, 1997;Preiss, 1997;Farré et al, 2001), and not in others (Geigenberger et al, 1994;Geiger et al, 1998;Trethewey et al, 1998Trethewey et al, , 1999Fernie et al, 2001).…”

Section: Hexose Phosphates and Glycolytic Intermediates Are Distributmentioning

confidence: 99%

Analysis of the Compartmentation of Glycolytic Intermediates, Nucleotides, Sugars, Organic Acids, Amino Acids, and Sugar Alcohols in Potato Tubers Using a Nonaqueous Fractionation Method

Farre¹

2001

Plant Physiology

127

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The compartmentation of metabolism in heterotrophic plant tissues is poorly understood due to the lack of data on metabolite distributions and fluxes between subcellular organelles. The main reason for this is the lack of suitable experimental methods with which intracellular metabolism can be measured. Here, we describe a nonaqueous fractionation method that allows the subcellular distributions of metabolites in developing potato (Solanum tuberosum L. cv Desiree) tubers to be calculated. In addition, we have coupled this fractionation method to a recently described gas chromatography-mass spectrometry procedure that allows the measurement of a wide range of small metabolites. To calculate the subcellular metabolite concentrations, we have analyzed organelle volumes in growing potato tubers using electron microscopy. The relative volume distributions in tubers are very similar to the ones for source leaves. More than 60% of most sugars, sugar alcohols, organic acids, and amino acids were found in the vacuole, although the concentrations of these metabolites is often higher in the cytosol. Significant amounts of the substrates for starch biosynthesis, hexose phosphates, and ATP were found in the plastid. However, pyrophosphate was located almost exclusively in the cytosol. Calculation of the mass action ratios of sucrose synthase, UDP-glucose pyrophosphorylase, phosphoglucosisomerase, and phosphoglucomutase indicate that these enzymes are close to equilibrium in developing potato tubers. However, due to the low plastidic pyrophosphate concentration, the reaction catalyzed by ADP-glucose pyrophosphorylase was estimated to be far removed from equilibrium.Compartmentation is one of the distinguishing characteristics of plant metabolism (ap Rees, 1987). A true understanding of the nature and regulation of plant metabolic networks can only be achieved when the metabolic interactions between subcellular compartments have been charted and subjected to analysis through experimental procedures. Because of the profound difficulties associated with measuring enzymes, metabolites, and fluxes in specific subcellular compartments, our understanding of plant metabolism has lagged far behind that of animal and microbial systems.Although methods have been developed for the assay of subcellular metabolite levels in leaf tissue (Stitt et al., 1989), and the interactions between plastidial and cytosolic metabolism during photosynthesis have been partially characterized (Stitt, 1997), little is known about the metabolic networks in heterotrophic cells. There are two main reasons for this. First, there is a lack of suitable methods for organelle isolation, which is a particularly difficult problem in heterotrophic cells because these often contain large starch grains that cause extra damage to the organelles during fractionation. Second, although leaf metabolism is highly conserved between different species (Heineke et al., 1997), heterotrophic tissues usually form differentiated organs with specific functions and therefore studies ca...

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Section: Hexose Phosphates and Glycolytic Intermediates Are Distributmentioning

confidence: 99%

Analysis of the Compartmentation of Glycolytic Intermediates, Nucleotides, Sugars, Organic Acids, Amino Acids, and Sugar Alcohols in Potato Tubers Using a Nonaqueous Fractionation Method

Farre¹

2001

Plant Physiology

127

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“…This would imply a reduction in carbon flow through cytosolic glycolysis if one assumes that pyruvate-dependent phosphofructokinase catalyzes a net glycolytic reaction in developing seeds of Arabidopsis, as has been postulated for developing potato tubers and tobacco sink leaves (Hajirezaei et al, 1994;Paul et al, 1995). The observation that pyruvate, the end product of glycolysis, can be taken up and be incorporated at high rates into fatty acids by isolated plastids of developing seeds of canola or castor (Smith et al, 1992;Kang and Rawsthorne, 1994) suggests that carbon flow from carbohydrates to triacylglycerols may involve extraplastidic glycolysis.…”

Section: Carbohydrate Metabolism Is Affected In the Wri1 Mutantmentioning

confidence: 99%

wrinkled1: A Novel, Low-Seed-Oil Mutant of Arabidopsis with a Deficiency in the Seed-Specific Regulation of Carbohydrate Metabolism1

1998

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During oil deposition in developing seeds of Arabidopsis, photosynthate is imported in the form of carbohydrates into the embryo and converted to triacylglycerols. To identify genes essential for this process and to investigate the molecular basis for the developmental regulation of oil accumulation, mutants producing wrinkled, incompletely filled seeds were isolated. A novel mutant locus, wrinkled1 (wri1), which maps to the bottom of chromosome 3 and causes an 80% reduction in seed oil content, was identified. Wildtype and homozygous wri1 mutant plantlets or mature plants were indistinguishable. However, developing homozygous wri1 seeds were impaired in the incorporation of sucrose and glucose into triacylglycerols, but incorporated pyruvate and acetate at an increased rate. Because the activities of several glycolytic enzymes, in particular hexokinase and pyrophosphate-dependent phosphofructokinase, are reduced in developing homozygous wri1 seeds, it is suggested that WRI1 is involved in the developmental regulation of carbohydrate metabolism during seed filling.

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“…The lack of a phenotype in response to moderate antisense suppression is consistent with results of severa1 other antisense experiments. For example, in studies in which antisense approaches were used to decrease the leve1 of pyrophosphate: Fru-6-P phosphotransferase, Fru-1,6-bisphosphatase, and citrate synthase, a greater than 80% decrease in enzyme levels was needed before changes in metabolism or phenotype were detected (Hajirezaei et al, 1994;Kossmann et al, 1994;Landschutze et al, 1995).…”

Section: A I 1 Plants Crown Under 60th High-and Low-light Conditions mentioning

confidence: 99%

Antisense Expression and Overexpression of Biotin Carboxylase in Tobacco Leaves

et al. 1997

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Although much is known about the biochemistry involved in the synthesis of fatty acids, comparatively little is understood about the regulation of this pathway. Recently, several-in vivo studies have implicated the plastidlocalized ACCase as a primary regulatory enzyme in fatty acid synthesis. Light activation of fatty acid synthesis in chloroplasts is controlled through the ACCase reaction (Post-Beittenmiller et al., 1991, 1992, and this enzyme was also identified as a regulatory step in the feedback inhibition of fatty acid synthesis in tobacco (Nicotiana tabacum) suspension cultures . Furthermore, Page et al. (1994) demonstrated that the plastid ACCase of maize (Zea muys L.) and barley (Hordeum vulgare) leaves exerts a high degree of flux control over fatty acid synthesis. These findings extend the observations from animal, fungal, and bacterial systems that implicate

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Transgenic potato plants with strongly decreased expression of pyrophosphate:fructose-6-phosphate phosphotransferase show no visible phenotype and only minor changes in metabolic fluxes in their tubers

Cited by 100 publications

References 60 publications

Analysis of the Compartmentation of Glycolytic Intermediates, Nucleotides, Sugars, Organic Acids, Amino Acids, and Sugar Alcohols in Potato Tubers Using a Nonaqueous Fractionation Method

Analysis of the Compartmentation of Glycolytic Intermediates, Nucleotides, Sugars, Organic Acids, Amino Acids, and Sugar Alcohols in Potato Tubers Using a Nonaqueous Fractionation Method

wrinkled1: A Novel, Low-Seed-Oil Mutant of Arabidopsis with a Deficiency in the Seed-Specific Regulation of Carbohydrate Metabolism1

Antisense Expression and Overexpression of Biotin Carboxylase in Tobacco Leaves

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