Journal article

Publication year: 2003

Pages: 1691-1700

Journal: Journal of Experimental Botany

Volume number: 54

Issue number: 388

ISSN: 0022-0957

Open access status: Bronze

DOI Link: https://doi.org/10.1093/jxb/erg191

Publisher: Oxford University Press

Abstract: 
Symbiotic dinitrogen fixation of legume nodules is fuelled by phloem-imported carbohydrates. These have to pass several cell layers to reach cells infected with Rhizobium bacteroids. It is unclear whether apoplastic steps are involved in carbohyd rate translocation within the nodule. Protoplasts were isolated from the infected and uninfected cells of the central tissue of Vicia faba nodules using a recently developed protocol. These protoplasts were used to elucidate pathways for sugar transport in this tissue. Both types of protoplasts released protons into the medium. Acidification was inhibited by vanadate and erythrosin B. However, it was stimulated by fusicoccin only in uninfected cells. A symport of sugars with protons can therefore be energized in both cell types. Uptake of C-14-labelled sugars was determined using a phthalate centrifugation technique. Uninfected protoplasts accumulated glucose through high-affinity H+/glucose-symport that was not competitively inhibited by fructose or sucrose. Uninfected protoplasts also absorbed sucrose with biphasic kinetics. At 0.1, 1, and 10 mM sucrose, uptake was inhibited by CCCP. Fusicoccin did not stimulate the linear phase of sucrose uptake. Glucose inhibited sucrose uptake nearly completely. This was not related to sucrose cleavage in the medium because sucrose was absorbed at a much higher rate than glucose, and glucose concentration did not increase in sucrose-containing protoplast suspensions. By contrast with uninfected protoplasts, infected cells did not show transporter-mediated glucose or sucrose uptake. The findings underline a role of uninfected cells in sugar translocation. Infected cells are not apoplastically supplied with sugars and possibly depend on uninfected cells for carbon supply.

Harvard Citation style: Peiter, E. and Schubert, S. (2003) Sugar uptake and proton release by protoplasts from the infected zone of Vicia faba L. nodules: evidence against apoplastic sugar supply of infected cells, Journal of Experimental Botany, 54(388), pp. 1691-1700. https://doi.org/10.1093/jxb/erg191

APA Citation style: Peiter, E., & Schubert, S. (2003). Sugar uptake and proton release by protoplasts from the infected zone of Vicia faba L. nodules: evidence against apoplastic sugar supply of infected cells. Journal of Experimental Botany. 54(388), 1691-1700. https://doi.org/10.1093/jxb/erg191