Highway or byway: the metabolic role of the GABA shunt in plants

Fait, Aaron; Fromm, Hillel; Walter, Dirk; Galili, Gad; Fernie, Alisdair R.

doi:10.1016/j.tplants.2007.10.005

Cited by 597 publications

(464 citation statements)

References 60 publications

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“…However, the observed increase in succinate also may have been due to enhanced synthesis from GABA, via the well-described pathway of Glu decarboxylase, GABA transaminase, and succinic semialdehyde dehydrogenase ( Fig. 4; Fait et al, 2008). It has already been proposed that the production of GABA is due to the acidification of the cytosol under anoxic conditions, which stimulates the activity of Glu decarboxylase (Ratcliffe, 1995).…”

Section: Linking Metabolite and Transcript Changes To Visualize Modifmentioning

confidence: 82%

Defining Core Metabolic and Transcriptomic Responses to Oxygen Availability in Rice Embryos and Young Seedlings

et al. 2009

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Analysis reveals that there is limited overlap in the sets of transcripts that show significant changes in abundance during anaerobiosis in different plant species. This may be due to the fact that a combination of primary effects, changes due to the presence or absence of oxygen, and secondary effects, responses to primary changes or tissue and developmental responses, are measured together and not differentiated from each other. In order to dissect out these responses, the effect of the presence or absence of oxygen was investigated using three different experimental designs using rice (Oryza sativa) as a model system. A total of 110 metabolites and 9,596 transcripts were found to change significantly in response to oxygen availability in at least one experiment. However, only one-quarter of these showed complementary responses to oxygen in all three experiments, allowing the core response to oxygen availability to be defined. A total of 10 metabolites and 1,136 genes could be defined as aerobic responders (up-regulated in the presence of oxygen and down-regulated in its absence), and 13 metabolites and 730 genes could be defined as anaerobic responders (up-regulated in the absence of oxygen and down-regulated in its presence). Defining core sets of transcripts that were sensitive to oxygen provided insights into alterations in metabolism, specifically carbohydrate and lipid metabolism and the putative regulatory mechanisms that allow rice to grow under anaerobic conditions. Transcript abundance of a specific set of transcription factors was sensitive to oxygen availability during all of the different experiments conducted, putatively identifying primary regulators of gene expression under anaerobic conditions. Combined with the possibility of selective transcript degradation, these transcriptional processes are involved in the core response of rice to anaerobiosis.

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Section: Linking Metabolite and Transcript Changes To Visualize Modifmentioning

confidence: 82%

Defining Core Metabolic and Transcriptomic Responses to Oxygen Availability in Rice Embryos and Young Seedlings

et al. 2009

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“…GABA is then transported through a putative GABA transporter into the mitochondrion where it is converted to succinic semialdehyde by GABA transaminase (GABAT) and then to succinate by succinic semialdehyde dehydrogenase (SSDH). GABAT can use either pyruvate or /-ketoglutarate to catalyze the conversion of GABA to succinic semialdehyde, leading to alanine or glutamate production, respectively, as side-products (Figure 3), both of which may serve to maintain the mitochondrial GABA-glutamate balance [92].…”

Section: Mitochondrial Metabolism Across the Alveolatamentioning

confidence: 99%

Apicomplexan Energy Metabolism: Carbon Source Promiscuity and the Quiescence Hyperbole

Jacot

Waller

Soldati‐Favre

et al. 2016

Trends in Parasitology

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Pages 15apicomplexan mitochondrion in energy generation has remained unclear, given the glucosereplete intracellular nature of the environmental niches of these parasites and the apparent reduction of mitochondrial metabolic pathways [4][5][6][7]. For example, apicomplexan mitochondria lack 'type I' NADH dehydrogenase (NDH, complex I of the ETC) and many apparently lack the enzymes and transporters required for fatty acid b-oxidation [8,9]. Furthermore, the pyruvate dehydrogenase complex (PDH) responsible for conversion of pyruvate into acetyl-CoA -an obligate fuel for the TCA cycle -is only present in the apicoplast [10]. Consequently, there was no obvious entry point to allow catalysis of glycolytic pyruvate by the TCA cycle [10][11][12][13][14]. Despite this, there is overwhelming evidence that apicomplexans rely on a functional and canonical TCA cycle (as reviewed [4,5,15]), and apicomplexan genome annotations indicate the presence of all enzymes of the TCA cycle. Only one clade of apicomplexans, Cryptosporidium spp., show evidence of outright loss of the TCA cycle, but these taxa retain only a highly reduced mitochondrion, the mitosome, and have also lost their apicoplast [5,8,16].This review highlights how metabolomics technologies coupled to genetic manipulation have helped in unraveling apicomplexan parasite plasticity in carbon source utilization through different life stages, revealing a complex and sometimes counter-intuitive pattern of metabolic gains, losses, and reassignments. These changes have presumably been tailored to allow these parasites to thrive within their various host niches, but may constitute some much-needed Achilles' heels in the fight against these devastating diseases. Plasmodium falciparum and the Glycolytic DeceitGlycolysis has long appeared to be the main source of ATP and NAD(P)H in the erythrocytic stages of the malaria parasites, [5,[17][18][19][20][21]. Indeed, glucose uptake in P. falciparum-infected red blood cells (RBCs) has been observed to increase 75-100-fold compared to uninfected RBC [22][23][24][25]. Up to 93% of glucose is converted directly to lactate in asexual stages [26][ 4 _ T D $ D I F F ] and is ultimately excreted into the surrounding host cell. Perturbation of glucose uptake is detrimental to parasite growth [27,28], suggesting that glycolysis is an important part of the parasite's strategy for rapid proliferation. In a manner analogous to the Warburg effect observed in highly-proliferative cancer lines and other rapidly-growing cells (e.g., yeast and bloodstream Trypanosoma spp.), Plasmodium (in erythrocytic stages) has opted for fast generation of ATP through substrate-level phosphorylation and secretion of lactate as an end-product (aerobic fermentative glycolysis), as opposed to the 'slow but efficient' mitochondrial oxidative phosphorylation and complete oxidation [29]. Reasons for this dependence on glycolytic fermentation remain unclear -after all, blood stages of Plasmodium certainly have access to oxygen -but it may be a way of avoiding excessiv...

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“…This particular behavior of GABA may indicate the presence of a metabolic pathway until germination starts, which is switched off during tube growth, but again is activated after blocking the oxidative phosphorylation. The GABA shunt linking the amino acid metabolism to the citrate cycle might be a likely candidate for this pathway (Fait et al, 2008).…”

Section: Amino Acidsmentioning

confidence: 99%

“…7). In plants, changes of GABA levels have been reported due to stress, signaling, energy production, and maintenance of carbon/nitrogen balance by linking the TCA cycle and amino acid metabolism by the so-called GABA shunt (Fait et al, 2008). Inhibition of the ATP production via antimycin A may thus reactivate the GABA shunt to generate pyruvate for ethanol production.…”

Section: Aerobic Fermentation and Gaba Shuntmentioning

confidence: 99%

Dynamic Adaption of Metabolic Pathways during Germination and Growth of Lily Pollen Tubes after Inhibition of the Electron Transport Chain

et al. 2013

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Investigation of the metabolome and the transcriptome of pollen of lily (Lilium longiflorum) gave a comprehensive overview of metabolic pathways active during pollen germination and tube growth. More than 100 different metabolites were determined simultaneously by gas chromatography coupled to mass spectrometry, and expressed genes of selected metabolic pathways were identified by next-generation sequencing of lily pollen transcripts. The time-dependent changes in metabolite abundances, as well as the changes after inhibition of the mitochondrial electron transport chain, revealed a fast and dynamic adaption of the metabolic pathways in the range of minutes. The metabolic state prior to pollen germination differed clearly from the metabolic state during pollen tube growth, as indicated by principal component analysis of all detected metabolites and by detailed observation of individual metabolites. For instance, the amount of sucrose increased during the first 60 minutes of pollen culture but decreased during tube growth, while glucose and fructose showed the opposite behavior. Glycolysis, tricarbonic acid cycle, glyoxylate cycle, starch, and fatty acid degradation were activated, providing energy during pollen germination and tube growth. Inhibition of the mitochondrial electron transport chain by antimycin A resulted in an immediate production of ethanol and a fast rearrangement of metabolic pathways, which correlated with changes in the amounts of the majority of identified metabolites, e.g. a rapid increase in g-aminobutyric acid indicated the activation of a g-aminobutyric acid shunt in the tricarbonic acid cycle, while ethanol fermentation compensated the reduced ATP production after inhibition of the oxidative phosphorylation.

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Highway or byway: the metabolic role of the GABA shunt in plants

Cited by 597 publications

References 60 publications

Defining Core Metabolic and Transcriptomic Responses to Oxygen Availability in Rice Embryos and Young Seedlings

Defining Core Metabolic and Transcriptomic Responses to Oxygen Availability in Rice Embryos and Young Seedlings

Apicomplexan Energy Metabolism: Carbon Source Promiscuity and the Quiescence Hyperbole

Dynamic Adaption of Metabolic Pathways during Germination and Growth of Lily Pollen Tubes after Inhibition of the Electron Transport Chain

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