Regulatory mechanisms of ion channels in xylem parenchyma cells

• Published in: Journal of experimental botany Vol. 48; no. Special; pp. 441 - 449
• Main Authors: de Boer, A.H., Wegner, L.H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford OXFORD UNIVERSITY PRESS 01.03.1997; Oxford University Press
• Subjects: Barley; Biological and medical sciences; Cell membranes; Cell physiology; Electric potential; Fundamental and applied biological sciences. Psychology; Guard cells; K+ and Na+ Pathways in Mineral Nutrition; Parenchyma; Pipettes; Plant cells; Plant physiology and development; Plant roots; Plants; Plasma membrane and permeation; Xylem; Electric potential; Monocotyledones; Xylem; Hordeum vulgare; Parenchyma; Ion transport; Signal transduction; Transpiration; Regulation(control); Gramineae; Hydrostatic pressure; Angiospermae; Spermatophyta; Models; Membrane channel; G protein
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/48.special_issue.441

Xylem parenchyma cells surround the xylem vessels and control the composition of the transpiration stream which flows through the vessels. In the plasma membrane of the xylem parenchyma cells, one inward rectifying channel (denoted KIRC) and two outward rectifying channels (denoted KORC and NORC) have been identified. In the present study it is shown that KIRC was activated by Gpp(NH)p, in contrast to the inward rectifier in guard cells. In the inside-out patch configuration, Gpp(NH)p elicited single channel KIRC activity as well and the conclusion is, therefore, that KIRC is G-protein regulated in a membrane-delimited fashion. NORC gating is affected by the calcium buffering capacity of the pipette solution as determined by the amount of EGTA. KORC conductance is shown to be strongly dependent upon the apoplastic K+-concentration. The role of the above-mentioned transporters and their regulation mechanisms are discussed in the light of root:shoot communication and long-distance signalling.