Specific Transport of Inorganic Phosphate and C3‐ and C6‐Sugar‐Phosphates across the Envelope Membranes of Tomato (Lycopersicon esculentum) Leaf‐Chloroplasts, Tomato Fruit‐Chloroplasts and Fruit‐Chromoplasts

Schünemann, Danja; Borchert, Sieglinde

doi:10.1111/j.1438-8677.1994.tb00821.x

Cited by 31 publications

(26 citation statements)

References 37 publications

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“…A general hexose phosphate translocator that transports Glc6P and, in addition, Glc1P has been demonstrated to exist in tomato fruits (Schünemann and Borchert, 1994) and wheat endosperm (Tetlow et al, 1996), or the presence of such an activity has been deduced indirectly from the observation of Glc1P-dependent starch synthesis, for example, in wheat endosperm (Tyson and ap Rees, 1988), maize Glucose 6-Phosphate Transporter 113 endosperm (Neuhaus et al, 1993), and potato tubers (Naeem et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…Because these plastids are normally not able to generate hexose phosphates from C3 compounds due to the absence of fructose 1,6-bisphosphatase activity (Entwistle and ap Rees, 1988), they rely on the import of cytosolically generated hexose phosphates as the source of carbon for starch biosynthesis and, in addition, for the oxidative pentose phosphate pathway. The results of transport measurements with intact organelles or reconstituted tissues from different plants suggest that this transport is mediated by a phosphate translocator that imports hexose phosphates in exchange with inorganic phosphate or C3 sugar phosphates (Borchert et al, 1989(Borchert et al, , 1993 Hill and Smith, 1991, 1995; Neuhaus et al, 1993; Flügge and Weber, 1994;Schünemann and Borchert, 1994;Flügge, 1995;Schott et al, 1995;Quick and Neuhaus, 1996).In nongreen tissues from most plants studied to date, glucose 6-phosphate (Glc6P) is the preferred hexose phosphate taken up by nongreen plastids. However, in amyloplasts from wheat endosperm, glucose 1-phosphate (Glc1P) rather than Glc6P is the precursor of starch biosynthesis (Tyson and ap Rees, 1988;Tetlow et al, 1994).…”

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Molecular Characterization of a Carbon Transporter in Plastids from Heterotrophic Tissues: The Glucose 6-Phosphate/Phosphate Antiporter

et al. 1998

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Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only ‫ف‬ 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates. INTRODUCTIONDuring C 3 photosynthesis, energy from solar radiation is used for the formation of phosphorylated C3 sugar phosphates, triose phosphates (trioseP), and 3-phosphoglycerate (3-PGA); these products are exported from the chloroplasts into the cytosol via the trioseP/3-PGA/phosphate translocator (TPT). In the mature leaves of most plants, the exported photosynthates are then used in the formation of sucrose, which is allocated via the phloem to the heterotrophic plant organs, such as young leaves, roots, seeds, fruits, or tubers. In these sink tissues, sucrose serves as a source of carbon and energy and is first cleaved by the action of invertases or sucrose synthase; the products of these reactions are converted into hexose phosphates.Nongreen plastids of heterotrophic tissues are carbohydrate-importing organelles and, in the case of amyloplasts of storage tissues, the site of starch synthesis. Because these plastids are normally not able to generate hexose phosphates from C3 compounds due to the absence of fructose 1,6-bisphosphatase activity (Entwistle and ap Rees, 1988), they rely on the import of cytosolically generated hexose phosphates as the source of carbon for starch biosynthesis and, in addition, for the oxidative pentose phosphate pathway. The results of transport measurements with intact organelles or reconstituted tissues from different plants suggest that thi...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Molecular Characterization of a Carbon Transporter in Plastids from Heterotrophic Tissues: The Glucose 6-Phosphate/Phosphate Antiporter

et al. 1998

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“…Interestingly, a similar situation has been demonstrated for other closely related types of plastid. Schu$ nemann and Borchet [26] showed that tomato fruit chloroplasts and chromoplasts are able to transport Glc1P in counter exchange with P i . In contrast, chloroplasts and chromoplasts purified from sweet pepper fruits (both species belong to the Solanaceae) were not able to import Glc1P ia a hexose phosphate transporter ( [13] ; H. E. Neuhaus, B. Camara, W. P. Quick, and T. Mo$ hlmann, unpublished work).…”

Section: Transport Of Glc6p P I and Other Phosphorylated Intermediatmentioning

confidence: 99%

“…The stimulatory effect of PEP on P i import has already been demonstrated for isolated pea root and embryo plastids [29,30], and for envelope membranes from tomato fruits [26]. It still remains unclear whether there is a specific metabolic requirement for PEP\P i exchange in heterotrophic plastids (e.g.…”

Section: Transport Of Glc6p P I and Other Phosphorylated Intermediatmentioning

confidence: 99%

ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

Möhlmann

Tjaden

Henrichs

et al. 1997

Biochemical Journal

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We recently developed a method of purifying amyloplasts from developing maize (Zea mays L.) endosperm tissue [Neuhaus, Thom, Batz and Scheibe (1993) Biochem. J. 296, [395][396][397][398][399][400][401]. In the present paper we analyse how glucose 6-phosphate (Glc6P) and other phosphorylated compounds enter the plastid compartment. Using a proteoliposome system in which the plastid envelope membrane proteins are functionally reconstituted, we demonstrate that this type of plastid is able to transport ["%C]Glc6P or [$#P]P i in counter exchange with P i , Glc6P, dihydroxyacetone phosphate and phosphoenolpyruvate. Glucose 1-phosphate, fructose 6-phosphate and ribose 5-phosphate do not act as substrates for counter exchange. Besides hexose phosphates, ADP-glucose (ADPGlc) also acts as a substrate for starch synthesis in isolated maize endosperm amyloplasts. This process exhibits saturation kinetics with increasing concentrations of exogenously supplied ["%C]ADPGlc, reaching a maximum at

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“…Acyl CoA thioesterase (ACT) was measured according to Schtinemann and Borchert (1994) Determination of phosphatidylcholine (PC) protein and Chl. The analysis of PC has been described previously (Matile and Schellenberg 1996).…”

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confidence: 99%

Localization of chlorophyllase in the chloroplast envelope

Matile

Schellenberg

Vicentini

1997

Planta

116

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Abstract.Chlorophyllase catalyzes the first step in the catabolic pathway of chlorophyll. It is a constitutive enzyme located in chloroplast membranes. In isolated plastids the hydrolysis of the endogenous chlorophyll does not take place unless the membranes are solubilized in the presence of detergent. The structural latency of chlorophyllase activity appears to be due to the differential locations of substrate and enzyme within the plastids. Envelope membranes prepared from both chloroplasts and gerontoplasts contain chlorophyllase activity. The isolation of envelopes is associated with a marked increase in chlorophyllase activity per unit of protein.Yields of chlorophyllase and of specific envelope markers in the final preparations are similar, suggesting that the enzyme may be located in the envelope. It is hypothesized that the breakdown of chlorophyll during leaf senescence requires a mechanism that mediates the transfer of chlorophyll from the thylakoidal pigment-protein complexes to the sites of catabolic reactions in the envelope.

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Specific Transport of Inorganic Phosphate and C₃‐ and C₆‐Sugar‐Phosphates across the Envelope Membranes of Tomato (Lycopersicon esculentum) Leaf‐Chloroplasts, Tomato Fruit‐Chloroplasts and Fruit‐Chromoplasts

Cited by 31 publications

References 37 publications

Molecular Characterization of a Carbon Transporter in Plastids from Heterotrophic Tissues: The Glucose 6-Phosphate/Phosphate Antiporter

Molecular Characterization of a Carbon Transporter in Plastids from Heterotrophic Tissues: The Glucose 6-Phosphate/Phosphate Antiporter

ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

Localization of chlorophyllase in the chloroplast envelope

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