Stimulation of Photosynthetic Starch Formation by Sequestration of Cytoplasmic Orthophosphate

Sheu-Hwa, Chen-She; Lewis, D. H.; Walker, David A.

doi:10.1111/j.1469-8137.1975.tb02625.x

Cited by 88 publications

(27 citation statements)

References 14 publications

(14 reference statements)

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“…A similar effect, the increase of mannose-6-phosphate with a concomitant decrease in inorganic phosphate, was observed for plants incubated on mannose (Loughman et al, 1989). Sheu-Hwa et al (1975) and Herold et al (1976) found an accumulation of starch in some plant species incubated on mannose. These authors speculated that the sequestration of inorganic phosphate by mannose-6-phosphate accumulation caused a reduction in the activity of the triose-phosphate translocator, thereby reducing the export of carbon from the chloroplast and inhibiting starch degradation.…”

Section: Discussionsupporting

confidence: 71%

“…In contrast to glucose, mannose is known to be toxic for plant growth, supposedly due to a sequestration of inorganic phosphate as mannose-6-phosphate (Herold et al, 1976;Sheu-Hwa et al, 1975). Similarly, galactose is highly toxic when supplied exogenously to plants in concentrations of 1-10 mM (Loughman et al, 1989;Maretzki and Thom, 1978).…”

Section: Introductionmentioning

confidence: 99%

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The role of UDP‐glucose epimerase in carbohydrate metabolism of Arabidopsis

Dörmann

Benning

1998

The Plant Journal

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SummaryUridine 5Ј-diphospho-glucose-4-epimerase (UDP-Glc epimerase) catalyses the reversible epimerization of UDPgalactose and UDP-glucose. In contrast to bacteria and yeast, expression of the UDP-Glc epimerase gene in Arabidopsis was found not to be induced by galactose. To elucidate the metabolic role of this enzyme, transgenic Arabidopsis plants expressing the respective cDNA in sense or antisense orientation were constructed, leading to a range of plant lines with different UDP-Glc epimerase activities. No alterations in morphology were observed and the relative amounts of different galactose-containing compounds were not affected if the plants were raised on soil. However, on agar plates in the presence of galactose, the growth of different lines was increasingly repressed with decreasing enzyme activity, and an increase in the UDP-Gal content was observed in parallel, whereas the UDP-Glc content was nearly constant. The amount of galactose in the cell wall was increased in plants with low UDP-Glc epimerase activity grown on galactose, whereas the cellulose content in the leaves was not altered. Furthermore, starch determined at different times of the day was highly abundant in plants with low UDP-Glc epimerase activity in the presence of galactose. It is proposed that low endogenous UDP-Glc epimerase activity is responsible for the galactose toxicity of the wild-type. Possible mechanisms by which the starch content might be modulated are discussed.

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Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

The role of UDP‐glucose epimerase in carbohydrate metabolism of Arabidopsis

Dörmann

Benning

1998

The Plant Journal

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“…Man-6-P is then only slowly processed by the plant, since the enzymes required for this are either absent or exist in very low concentrations (Sheu-Hwa et al, 1975;Walker and Sivak, 1986). Due to this property, Man has been used in the past to provoke ATP and phosphate depletion in adult leaves of some plant species (Siegl and Stitt, 1990;Van Quy and Champigny, 1992).…”

Section: Phosphate and Atp Levels And Repression Of Germinationmentioning

confidence: 99%

Mannose Inhibits Arabidopsis Germination via a Hexokinase-Mediated Step1

1999

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Low concentrations of the glucose (Glc) analog mannose (Man) inhibit germination of Arabidopsis seeds. Man is phosphorylated by hexokinase (HXK), but the absence of germination was not due to ATP or phosphate depletion. The addition of metabolizable sugars reversed the Man-mediated inhibition of germination. Carbohydrate-mediated regulation of gene expression involving a HXK-mediated pathway is known to be activated by Glc, Man, and other monosaccharides. Therefore, we investigated whether Man blocks germination through this system. By testing other Glc analogs, we found that 2-deoxyglucose, which, like Man, is phosphorylated by HXK, also blocked germination; no inhibition was observed with 6-deoxyglucose or 3-O-methylglucose, which are not substrates for HXK. Since these latter two sugars are taken up at a rate similar to that of Man, uptake is unlikely to be involved in the inhibition of germination. Furthermore, we show that mannoheptulose, a specific HXK inhibitor, restores germination of seeds grown in the presence of Man. We conclude that HXK is involved in the Man-mediated repression of germination of Arabidopsis seeds, possibly via energy depletion.Among the many regulatory systems and signals in plants, carbon-metabolite-mediated gene regulation has been receiving growing attention in the past few years (for reviews, see

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“…For example, the analogs 3-O-methylglucose and 6-deoxyglucose are neither metabolized nor phosphorylated by hexokinase. By contrast, the glucose analog 2-deoxyglucose and a glucose isomer, mannose can be phosphorylated by hexokinase, but do not undergo additional glycolysis, because of the absence of the 2-hydroxyl group in 2-deoxyglucose and the inefficient catalytic activities of both hexose phosphate isomerase and hexose 6-phosphate dehydrogenase in plants (Loughman et al, 1989;Salas et al, 1965;Sheu-Hwa et al, 1975). We used the same strategy of feeding experiments that involved glucose analogs and different kinds of sugars, categorizing those 3 classes of genes into 2 groups that rely on either hexokinase-dependent or -independent sugar signaling.…”

mentioning

confidence: 99%

Differential Anoxic Expression of Sugar-Regulated Genes Reveals Diverse Interactions between Sugar and Anaerobic Signaling Systems in Rice

Lim

Lee

Yim

et al. 2013

Molecules and Cells

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The interaction between the dual roles of sugar as a metabolic fuel and a regulatory molecule was unveiled by examining the changes in sugar signaling upon oxygen deprivation, which causes the drastic alteration in the cellular energy status. In our study, the expression of anaerobically induced genes is commonly responsive to sugar, either under the control of hexokinase or non-hexokinase mediated signaling cascades. Only sugar regulation via the hexokinase pathway was susceptible for O 2 deficiency or energy deficit conditions evoked by uncoupler. Examination of sugar regulation of those genes under anaerobic conditions revealed the presence of multiple paths underlying anaerobic induction of gene expression in rice, subgrouped into three distinct types. The first of these, which was found in type-1 genes, involved neither sugar regulation nor additional anaerobic induction under anoxia, indicating that anoxic induction is a simple result from the release of sugar repression by O 2 -deficient conditions. In contrast, type-2 genes also showed no sugar regulation, albeit with enhanced expression under anoxia. Lastly, expression of type-3 genes is highly enhanced with sugar regulation sustained under anoxia. Intriguingly, the inhibition of the mitochondrial ATP synthesis can reproduce expression pattern of a specific set of anaerobically induced genes, implying that rice cells may sense O 2 deprivation, partly via perception of the perturbed cellular energy status. Our study of interaction between sugar signaling and anaerobic conditions has revealed that sugar signaling and the cellular energy status are likely to communicate with each other and influence anaerobic induction of gene expression in rice.

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Stimulation of Photosynthetic Starch Formation by Sequestration of Cytoplasmic Orthophosphate

Cited by 88 publications

References 14 publications

The role of UDP‐glucose epimerase in carbohydrate metabolism of Arabidopsis

The role of UDP‐glucose epimerase in carbohydrate metabolism of Arabidopsis

Mannose Inhibits Arabidopsis Germination via a Hexokinase-Mediated Step1

Differential Anoxic Expression of Sugar-Regulated Genes Reveals Diverse Interactions between Sugar and Anaerobic Signaling Systems in Rice

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