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Gluconeogenesis: definition, steps, regulation, and …

12/05/2005 · Trehalose 6-phosphate regulates starch synthesis via posttranslational redox activation of ..

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Here, trehalose is synthesized by a multienzyme complex containing trehalose-6-phosphate synthase (T6PS) encoded by TPS1, a trehalose-6-phosphatase encoded by TPS2, and two regulatory subunits encoded by the TSL1 and TPS3 genes (; ).

Glycogen synthesis is, unlike its breakdown, endergonic—it requires the input of energy

The filamentous fungus Magnaporthe oryzae is the causal agent of rice blast disease. Here we show that glycogen metabolic genes play an important role in plant infection by M. oryzae. Targeted deletion of AGL1 and GPH1, which encode amyloglucosidase and glycogen phosphorylase, respectively, prevented mobilisation of glycogen stores during appressorium development and caused a significant reduction in the ability of M. oryzae to cause rice blast disease. By contrast, targeted mutation of GSN1, which encodes glycogen synthase, significantly reduced the synthesis of intracellular glycogen, but had no effect on fungal pathogenicity. We found that loss of AGL1 and GPH1 led to a reduction in expression of TPS1 and TPS3, which encode components of the trehalose-6-phosphate synthase complex, that acts as a genetic switch in M. oryzae. Tps1 responds to glucose-6-phosphate levels and the balance of NADP/NADPH to regulate virulence-associated gene expression, in association with Nmr transcriptional inhibitors. We show that deletion of the NMR3 transcriptional inhibitor gene partially restores virulence to a Δagl1Δgph1 mutant, suggesting that glycogen metabolic genes are necessary for operation of the NADPH-dependent genetic switch in M. oryzae.

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Trehalose 6-phosphate regulates starch synthesis via posttranslational redox activation of ADP-glucose pyrophosphorylase.

Trehalose is the most widespread disaccharide in nature, occurring in bacteria, fungi, insects, and plants. Its precursor, trehalose 6-phosphate (T6P), is also indispensable for the regulation of sugar utilization and growth, but the sites of action are largely unresolved. Here we use genetic and biochemical approaches to investigate whether T6P acts to regulate starch synthesis in plastids of higher plants. Feeding of trehalose to Arabidopsis leaves led to stimulation of starch synthesis within 30 min, accompanied by activation of ADP-glucose pyrophosphorylase (AGPase) via posttranslational redox modification. The response resembled sucrose but not glucose feeding and depended on the expression of SNF1-related kinase. We also analyzed transgenic Arabidopsis plants with T6P levels increased by expression of T6P synthase or decreased by expression of T6P phosphatase (TPP) in the cytosol. Compared with wild type, leaves of T6P synthase-expressing plants had increased redox activation of AGPase and increased starch, whereas TPP-expressing plants showed the opposite. Moreover, TPP expression prevented the increase in AGPase activation in response to sucrose or trehalose feeding. Incubation of intact isolated chloroplasts with 100 μM T6P significantly and specifically increased reductive activation of AGPase within 15 min. Results provide evidence that T6P is synthesized in the cytosol and acts on plastidial metabolism by promoting thioredoxin-mediated redox transfer to AGPase in response to cytosolic sugar levels, thereby allowing starch synthesis to be regulated independently of light. The discovery informs about the evolution of plant metabolism and how chloroplasts of prokaryotic origin use an intermediate of the ancient trehalose pathway to report the metabolic status of the cytosol.

AB - The filamentous fungus Magnaporthe oryzae is the causal agent of rice blast disease. Here we show that glycogen metabolic genes play an important role in plant infection by M. oryzae. Targeted deletion of AGL1 and GPH1, which encode amyloglucosidase and glycogen phosphorylase, respectively, prevented mobilisation of glycogen stores during appressorium development and caused a significant reduction in the ability of M. oryzae to cause rice blast disease. By contrast, targeted mutation of GSN1, which encodes glycogen synthase, significantly reduced the synthesis of intracellular glycogen, but had no effect on fungal pathogenicity. We found that loss of AGL1 and GPH1 led to a reduction in expression of TPS1 and TPS3, which encode components of the trehalose-6-phosphate synthase complex, that acts as a genetic switch in M. oryzae. Tps1 responds to glucose-6-phosphate levels and the balance of NADP/NADPH to regulate virulence-associated gene expression, in association with Nmr transcriptional inhibitors. We show that deletion of the NMR3 transcriptional inhibitor gene partially restores virulence to a Δagl1Δgph1 mutant, suggesting that glycogen metabolic genes are necessary for operation of the NADPH-dependent genetic switch in M. oryzae.

Glycoside hydrolase - Wikipedia

Glycoside hydrolases are found in essentially all domains of life

Recently, trehalose metabolism has been implicated in the regulation of sugar utilization in yeast and plants (-). Trehalose, an ancient sugar consisting of two α-1,1-linked glucose molecules, is synthesized via the phosphorylated precursor trehalose 6-phosphate (T6P), with a trehalose phosphate synthase (TPS) and a trehalose phosphate phosphatase (TPP). Disruption of AtTPS1 in Arabidopsis mutants led to an arrest in embryo development early in the phase of cell expansion and storage-reserve deposition (). Studies on transgenic lines overexpressing TPS or TPP identified T6P as essential for sugar utilization and growth in Arabidopsis plants (). External feeding of trehalose or sucrose to wild-type Arabidopsis led to an increase in T6P level within 30 min or 2 h, respectively, indicating a link between sugars and T6P that responds within a short time frame (). However, the sites of T6P action remain largely unknown.

To investigate a role of T6P in the regulation of starch synthesis, we (i) measured posttranslational redox activation of AGPase and starch accumulation after short-term feeding of trehalose to wild-type potato tubers and Arabidopsis leaves, (ii) analyzed the same parameters in leaves of transgenic Arabidopsis plants with altered T6P levels due to overexpression of heterologous TPS or TPP in their cytosol, and (iii) provided T6P directly to purified chloroplasts to investigate whether it affects redox activation of AGPase. The results provide genetic and biochemical evidence that T6P reports the cytosolic sucrose status to the plastid, leading to a stimulation of starch synthesis in response to sucrose by promoting reductive activation of AGPase.

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  • 08/11/2017 · The role of trehalose ..

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Trehalose metabolism in plants: Trends in Plant Science

Our results provide evidence that T6P regulates utilization of sugars for storage starch synthesis by promoting reductive activation of AGPase in the plastid. During the evolution of plants, chloroplasts that are of prokaryotic origin have used this intermediate of the ancient trehalose pathway to regulate their own metabolism relative to the metabolic requirements of the cytosol. The discovery helps us to understand the evolution of plant metabolism and how trehalose metabolism has been adapted as an indispensable regulatory component of carbon utilization for growth, storage, and survival in a diverse range of organisms.

A Selaginella lepidophylla Trehalose-6 ..

Trehalose is an ancient disaccharide ubiquitous in bacteria, fungi, insects, and plants, functioning as a reserve carbohydrate in bacteria, component of the haemolymph system of insects, and as a general stress protectant. Recent studies show that the precursor of trehalose, T6P, is an indispensable regulator of sugar utilization in eukaryotic organisms as different as yeasts and plants (, , ). However, apart from regulating glycolysis by inhibiting hexokinase in some yeast species, other sites of T6P action have until now not been known (, -). No target of T6P has been found in plants, where hexokinases are insensitive to T6P (). Here we provide independent lines of genetic and biochemical evidence that T6P acts indirectly on AGPase to promote posttranslational redox activation of the enzyme in response to sucrose, thereby controlling starch synthesis independently of light signals.

22/12/2017 · The regulation of trehalose in insects

Trehalose‐6‐phosphate, the intermediate of trehalose synthesis, is a signal of sucrose availability in plant cells, regulating photoassimilate partitioning in leaves and the utilisation of sucrose in sink organs.

Regulation of expression of trehalose-6-phosphate …

N2 - The filamentous fungus Magnaporthe oryzae is the causal agent of rice blast disease. Here we show that glycogen metabolic genes play an important role in plant infection by M. oryzae. Targeted deletion of AGL1 and GPH1, which encode amyloglucosidase and glycogen phosphorylase, respectively, prevented mobilisation of glycogen stores during appressorium development and caused a significant reduction in the ability of M. oryzae to cause rice blast disease. By contrast, targeted mutation of GSN1, which encodes glycogen synthase, significantly reduced the synthesis of intracellular glycogen, but had no effect on fungal pathogenicity. We found that loss of AGL1 and GPH1 led to a reduction in expression of TPS1 and TPS3, which encode components of the trehalose-6-phosphate synthase complex, that acts as a genetic switch in M. oryzae. Tps1 responds to glucose-6-phosphate levels and the balance of NADP/NADPH to regulate virulence-associated gene expression, in association with Nmr transcriptional inhibitors. We show that deletion of the NMR3 transcriptional inhibitor gene partially restores virulence to a Δagl1Δgph1 mutant, suggesting that glycogen metabolic genes are necessary for operation of the NADPH-dependent genetic switch in M. oryzae.

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