Phosphate-Mediated Increase of the Sieve-tube Conductance in Ricinus communis L. Seedlings is Accompanied by a Marked Acidification of the Sieve-tube Sap

Zhong, Wenjun; Langenberger, Silke; Komor, Ewald; Schobert, Christian

doi:10.1016/s0176-1617(11)81770-0

Cited by 4 publications

(3 citation statements)

References 21 publications

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“…The functioning of higher plants is controlled by complex signaling networks. Regulatory cascades that likely impact photoassimilate translocation may include (i) changes during the sink-to-source transition, (ii) the synthesis and operation of sucrose carriers, proton-ATPases and ion channels within the companion cellsieve element (CC-SE) complex (Schobert et al 1998), and (iii) the control of sieve-tube conductance (Zhong et al 1995). Some of the proteins identi®ed in the present study may well participate in such regulatory networks.…”

Section: Discussionmentioning

confidence: 81%

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Schobert

Baker

Szederkényi

et al. 1998

Planta

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116

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The mature, functional sieve-tube system in higher plants is dependent upon protein import from the companion cells to maintain a functional long-distance transport system. Soluble proteins present within the sieve-tube lumen were investigated by analysis of sievetube exudates which revealed the presence of distinct sets of polypeptides in seven monocotyledonous and dicotyledonous plant species. Antibodies directed against sieve-tube exudate proteins from Ricinus communis L. demonstrated the presence of shared antigens in the phloem sap collected from Triticum aestivum L., Oryza sativa L., Yucca ®lamentosa L., Cucurbita maxima Duch., Robinia pseudoacacia L. and Tilia platyphyllos L. Speci®c antibodies were employed to identify major polypeptides. Molecular chaperones related to Rubiscosubunit-binding protein and cyclophilin, as well as ubiquitin and the redox proteins, thioredoxin h and glutaredoxin, were detected in the sieve-tube exudate of all species examined. Actin and pro®lin, a modulator of actin polymerization, were also present in all analyzed phloem exudates. However, some proteins were highly species-speci®c, e.g. cystatin, a protease-inhibitor was present in R. communis but was not detected in exudates from other species, and orthologs of the well-known squash phloem lectin, phloem protein 2, were only identi®ed in the sieve-tube exudate of R. communis and R. pseudoacacia. These ®ndings are discussed in terms of the likely roles played by phloem proteins in the maintenance and function of the enucleate sieve-tube system of higher plants.

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Section: Discussionmentioning

confidence: 81%

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Schobert

Baker

Szederkényi

et al. 1998

Planta

Self Cite

116

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“…This result contrasts with that gained from seedlings exuding continuously. Under these conditions, the ATP concentration in the phloem sap decreased sharply after about 5 h (Zhong et al 1995).…”

Section: Resultsmentioning

confidence: 96%

“…The incubation medium of the cotyledons contained 5 mM Mes-KOH, 0.2 mM CaCl 2 , pH 5.5, and sucrose at the indicated concentrations. Calcium chloride was included, in contrast to former studies (Kallarackal et al 1989;Orlich and Komor 1992;Zhong et al 1995), because the sucrose concentration in the phloem sap decreased during extended incubation without CaCl 2 . The fresh weight of the cotyledons ranged between 140 and 190 mg.…”

Section: Methodsmentioning

confidence: 99%

Analysis of the driving forces of phloem transport in Ricinus seedlings: sucrose export and volume flow are determined by the source

Orlich

1998

Planta

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The aim of this study was to reveal the factors determining sucrose export and volume¯ow through the sieve tubes in Ricinus communis L. seedlings. The cotyledons take up sucrose from the apoplasm in vivo, and export most of it to the growing sinks, hypocotyl and root. This simple source-sink system allowed sucrose uptake and export to be studied under controlled conditions with respect to apoplasmic sucrose concentrations. From the additional knowledge of the sucrose concentrations in the mesophyll and the sieve tubes, transmembrane concentration dierences were calculated. The volume¯ow rate along the sieve tubes could be calculated from the export rate and the sucrose concentration in the sieve tubes. While the export rate exhibited saturation kinetics, the volume¯ow rate decreased at high external sucrose concentrations. The export rate correlated with the sucrose uptake rate, the volume¯ow rate correlated with the sucrose concentration (osmotic pressure) dierence across the sieve-tube plasma membrane, the driving force for transmembrane water¯ux. From these data it can be concluded that sucrose export and the volume¯ow through the sieve tubes are determined by activities of the source. Export out of Ricinus cotyledons was considerably higher than export out of green source leaves of dierent species. The concomitant comparatively low sucrose concentration in the sieve-tube sap of the seedlings can thus be attributed to a very high water¯ux into and along the sieve tubes associated with the high sucrose¯ux.

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CYCLCROP Mapping of ¹³ C Labelled Compounds: Perspectives in Polymer Science and Plant Physiology

Heidenreich

Spyros

Köckenberger

et al. 1998

Spatially Resolved Magnetic Resonance

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Phosphate-Mediated Increase of the Sieve-tube Conductance in Ricinus communis L. Seedlings is Accompanied by a Marked Acidification of the Sieve-tube Sap

Cited by 4 publications

References 21 publications

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Analysis of the driving forces of phloem transport in Ricinus seedlings: sucrose export and volume flow are determined by the source

CYCLCROP Mapping of ¹³ C Labelled Compounds: Perspectives in Polymer Science and Plant Physiology

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Phosphate-Mediated Increase of the Sieve-tube Conductance in Ricinus communis L. Seedlings is Accompanied by a Marked Acidification of the Sieve-tube Sap

Cited by 4 publications

References 21 publications

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Identification of immunologically related proteins in sieve-tube exudate collected from monocotyledonous and dicotyledonous plants

Analysis of the driving forces of phloem transport in Ricinus seedlings: sucrose export and volume flow are determined by the source

CYCLCROP Mapping of 13 C Labelled Compounds: Perspectives in Polymer Science and Plant Physiology

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CYCLCROP Mapping of ¹³ C Labelled Compounds: Perspectives in Polymer Science and Plant Physiology