Transport Processes and Corresponding Changes in Metabolite Levels in Relation to Starch Synthesis in Barley (<i>Hordeum vulgare</i> L.) Etioplasts

Bätz, Olaf; Scheibe, Renate; Neuhaus, H. Ekkehard

doi:10.1104/pp.100.1.184

Cited by 34 publications

(32 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The uracil uptake into isolated cauliflower bud amyloplasts was studied using the silicone-oil filtration method (Heldt and Sauer, 1971) with modifications (Batz et al, 1992). This method enables the quantitative separation of isolated plastids from the incubation medium by centrifugation.…”

Section: Uptake Experiments With Isolated Cauliflower Bud Amyloplastsmentioning

confidence: 99%

“…To study uracil uptake, 100 mL of the isolated cauliflower bud amyloplasts (2 mg protein/mL) was added to the same volume of an uptake medium consisting of 15 mM HEPES-KOH, pH 7.2, 2 mM MgCl 2 , 1 mM EDTA, and 0.3 M sorbitol and [ 14 C]-uracil (10 12 Bq mol 21 ). Termination of the transport process was achieved by separation of the plastids from the incubation medium by centrifugation of the samples at 12,000g through the silicone oil (Microfuge E; Beckman; see details in Batz et al, 1992). Radioactivity appearing in the supernatant was quantified by beta counting in a Packard Tricarb 2500 (Packard).…”

Section: Uptake Experiments With Isolated Cauliflower Bud Amyloplastsmentioning

confidence: 99%

See 1 more Smart Citation

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

et al. 2012

View full text Add to dashboard Cite

Nucleotide de novo synthesis is highly conserved among organisms and represents an essential biochemical pathway. In plants, the two initial enzymatic reactions of de novo pyrimidine synthesis occur in the plastids. By use of green fluorescent protein fusions, clear support is provided for a localization of the remaining reactions in the cytosol and mitochondria. This implies that carbamoyl aspartate, an intermediate of this pathway, must be exported and precursors of pyrimidine salvage (i.e., nucleobases or nucleosides) are imported into plastids. A corresponding uracil transport activity could be measured in intact plastids isolated from cauliflower (Brassica oleracea) buds. PLUTO (for plastidic nucleobase transporter) was identified as a member of the Nucleobase:Cation-Symporter1 protein family from Arabidopsis thaliana, capable of transporting purine and pyrimidine nucleobases. A PLUTO green fluorescent protein fusion was shown to reside in the plastid envelope after expression in Arabidopsis protoplasts. Heterologous expression of PLUTO in an Escherichia coli mutant lacking the bacterial uracil permease uraA allowed a detailed biochemical characterization. PLUTO transports uracil, adenine, and guanine with apparent affinities of 16.4, 0.4, and 6.3 mM, respectively. Transport was markedly inhibited by low concentrations of a proton uncoupler, indicating that PLUTO functions as a proton-substrate symporter. Thus, a protein for the absolutely required import of pyrimidine nucleobases into plastids was identified.

show abstract

Section: Uptake Experiments With Isolated Cauliflower Bud Amyloplastsmentioning

confidence: 99%

Section: Uptake Experiments With Isolated Cauliflower Bud Amyloplastsmentioning

confidence: 99%

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

et al. 2012

View full text Add to dashboard Cite

show abstract

“…In heterotrophic tissues starch synthesis is dependent on the supply of carbon skeletons from the cytosol. A number of studies have been made of the transporters that mediate the uptake of carbon precursors for starch synthesis in plastids from a variety of different tissues (Borchert et al, 1989(Borchert et al, , 1993Batz et al, 1992). However, at present a minimal amount of information is known about the modes by which precursors are taken up across the plastid envelope for fatty acid synthesis in heterotrophic tissue from any plant species.…”

mentioning

confidence: 99%

Evidence That a Malate/Inorganic Phosphate Exchange Translocator Imports Carbon across the Leucoplast Envelope for Fatty Acid Synthesis in Developing Castor Seed Endosperm

1997

View full text Add to dashboard Cite

In this study we examined the processes by which malate and pyruvate are taken up across the leucoplast envelope for fatty acid synthesis in developing castor (Ricinus communis L.) seed endosperm. Malate was taken up by isolated leucoplasts with a concentration dependence indicative of protein-mediated transport.The maximum rate of malate uptake was 704 f 41 nmol mg-' protein h-' and the K,,, was 0.62 f 0.08 mM. In contrast, the rate of pyruvate uptake increased linearly with respect to the substrate concentration and was 5-fold less than malate at a concentration of 5 mM. Malate uptake was inhibited by inorganic phosphate (Pi), glutamate, malonate, succinate, 2-oxoglutarate, and n-butyl malonate, an inhibitor of the mitochondrial malate/Pi-exchange translocator. Back-exchange experiments confirmed that malate was taken up by leucoplasts in counterexchange for Pi. The exchange stoichiometry was 1:l. The rate of malate-dependent fatty acid synthesis by isolated leucoplasts was 3-fold greater than from pyruvate at a concentration of 5 mM and was inhibited by n-butyl malonate. It is proposed that leucoplasts from developing castor endosperm contain a malate/Pi translocator that imports malate for fatty acid synthesis. This type of dicarboxylate transport activity has not been identified previously in plastids.During seed development the major metabolic activity of castor (Ricinus communis L.) endosperm is involved with the conversion of Suc to storage lipids (Canvin, 1963). This pathway involves the metabolism in severa1 subcellular compartments, which must interact by means of common intermediates. A key component of the pathway is de novo fatty acid synthesis, which is located in the plastid. In vitro studies using isolated leucoplasts from developing castor endosperm have demonstrated that carbon can be incorporated into fatty acids from a variety of potential precursors, including glycolytic intermediates, malate, and acetate (Mil The John

show abstract

“…The mitochondrial ADP/ATP carrier mediates the export of ATP that is synthesized in the mitochondrion to provide energy for cellular metabolism (Heimpel et al, 2001;Haferkamp et al, 2002). The plastidial ATP/ADP transporter (nucleotide transporter) is involved in ATP uptake by both chloroplasts and heterotrophic plastids, to enable the nocturnal ATP supply required for chlorophyll biosynthesis (Reiser et al, 2004;Reinhold et al, 2007), as well as by heterotrophic plastids to drive starch biosynthesis (Batz et al, 1992;Tjaden et al, 1998). Yet another ATP/ADP antiporter located in the endoplasmic reticulum (ER) membrane provides energy by importing ATP into the ER for the accumulation of ERrelated storage lipids and proteins (Leroch et al, 2008).…”

mentioning

confidence: 99%

Peroxisomal ATP Import Is Essential for Seedling Development inArabidopsis thaliana

et al. 2008

Self Cite

View full text Add to dashboard Cite

Several recent proteomic studies of plant peroxisomes indicate that the peroxisomal matrix harbors multiple ATPdependent enzymes and chaperones. However, it is unknown whether plant peroxisomes are able to produce ATP by substrate-level phosphorylation or whether external ATP fuels the energy-dependent reactions within peroxisomes. The existence of transport proteins that supply plant peroxisomes with energy for fatty acid oxidation and other ATP-dependent processes has not previously been demonstrated. Here, we describe two Arabidopsis thaliana genes that encode peroxisomal adenine nucleotide carriers, PNC1 and PNC2. Both proteins, when fused to enhanced yellow fluorescent protein, are targeted to peroxisomes. Complementation of a yeast mutant deficient in peroxisomal ATP import and in vitro transport assays using recombinant transporter proteins revealed that PNC1 and PNC2 catalyze the counterexchange of ATP with ADP or AMP. Transgenic Arabidopsis lines repressing both PNC genes were generated using ethanol-inducible RNA interference. A detailed analysis of these plants showed that an impaired peroxisomal ATP import inhibits fatty acid breakdown during early seedling growth and other b-oxidation reactions, such as auxin biosynthesis. We show conclusively that PNC1 and PNC2 are essential for supplying peroxisomes with ATP, indicating that no other ATP generating systems exist inside plant peroxisomes.

show abstract

Transport Processes and Corresponding Changes in Metabolite Levels in Relation to Starch Synthesis in Barley (Hordeum vulgare L.) Etioplasts

Abstract: Intact etioplasts with an intactness of 85% and with a cytosolic and a mitochondrial contamination of less than 10% were isolated from 8-d-old dark-grown barley (Hordeum vulgare)

Cited by 34 publications

References 21 publications

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

De Novo Pyrimidine Nucleotide Synthesis Mainly Occurs outside of Plastids, but a Previously Undiscovered Nucleobase Importer Provides Substrates for the Essential Salvage Pathway in Arabidopsis

Evidence That a Malate/Inorganic Phosphate Exchange Translocator Imports Carbon across the Leucoplast Envelope for Fatty Acid Synthesis in Developing Castor Seed Endosperm

Peroxisomal ATP Import Is Essential for Seedling Development inArabidopsis thaliana

Contact Info

Product

Resources

About