Transmembrane electron transport in sealed and NAD(P)H‐loaded right‐side‐out plasma membrane vesicles isolated from maize (Zea mays L.) roots

• Published in: Journal of experimental botany Vol. 55; no. 401; pp. 1343 - 1349
• Main Authors: Menckhoff, Mathias, Lüthje, Sabine
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.06.2004; Oxford Publishing Limited (England)
• Subjects: Biological and medical sciences; Biological Transport - drug effects; Calcium; Calcium - pharmacology; Cell Membrane - drug effects; Cell Membrane - physiology; Cell membranes; Cell physiology; Corn; diphenylene iodonium; Edetic Acid - pharmacology; Electron Transport - drug effects; Ferricyanides - metabolism; Ferricyanides - pharmacology; Fundamental and applied biological sciences. Psychology; Iron; NAD(P)H‐loaded vesicles; NADP - metabolism; Onium Compounds - pharmacology; Oxidation; Phosphates; Plant physiology; Plant physiology and development; Plant roots; Plant Roots - physiology; Plants; plasma membrane; Plasma membrane and permeation; Protons; Research Papers: Cell and Molecular Biology, Biochemistry and Molecular Physiology; transmembrane electron transport; Transport Vesicles - drug effects; Transport Vesicles - physiology; Warfarin - pharmacology; Zea mays; Zea mays - physiology; NAD(P)H-loaded vesicles; Monocotyledones; Warfarin; Zea mays; Root; Calcium; Gramineae; diphenylene iodonium; Angiospermae; Plasma membrane; Spermatophyta; transmembrane electron transport
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erh155

Electron transport across plasma membranes has been observed in vivo in several plant species and tissues after the application of ferricyanide (hexacyanoferrate III, HCF III). In the present work, a transmembrane electron flow was demonstrated in sealed and NAD(P)H–loaded right‐side‐out (apoplastic‐side‐out) plasma membrane vesicles isolated from maize (Zea mays L.) roots. HCF III was reduced at a rate of up to 126 nmol min–1 mg–1 protein by NADPH‐loaded vesicles, while reduction rates with NADH‐loaded vesicles were several‐fold lower. Coincident with the reduction of HCF III, NAD(P)H oxidation was observed inside the vesicles. The dependence of reduction on K+ indicated an electrogenic transmembrane electron flow. Application of 100 µM calcium decreased HCF III reduction up to 66%, while pre‐incubation with 200 µM warfarin or diphenylene iodonium inhibited transmembrane electron transport only weakly. Fe3+‐EDTA was not reduced significantly by NADPH‐loaded plasma membrane vesicles, whereas XTT was reduced at a rate of 765 pmol min–1 mg–1 protein. The results suggested a major function for NADPH in transmembrane electron flow and were discussed in conjunction with in vivo experiments.