Calcium activation of Mougeotia potassium channels

Phytochrome mediates chloroplast movement in the alga Mougeotia, possibly via changes in cytosolic calcium. It is known to regulate a calcium-activated potassium channel in the algal plasma membrane. As part of a characterization of the potassium channel, we examined the properties of calcium activa...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1990-03, Vol.92 (3), p.831-836
Main Authors: Lew, R.R. (York University, North York, Ontario, Canada), Serlin, B.S, Schauf, C.L, Stockton, M.E
Format: Article
Language:English
Subjects:
ALGAE
ALGUE
biochemical phenomena
Biological and medical sciences
Biology
CALCIO
CALCIUM
Cell membranes
Cell physiology
Chloroplasts
ESTRUCTURA CELULAR
Freshwater
Fundamental and applied biological sciences. Psychology
ION
Ion channels
IONES
Mougeotia
Physiological regulation
phytochrome
PIGMENT
PIGMENTOS
Plant cells
plant physiology
Plant physiology and development
Plasma membrane and permeation
plasma membranes
PLASTE
PLASTIDIOS
POTASIO
POTASSIUM
Potassium channels
Rotation
STRUCTURE CELLULAIRE
TRANSPORT DES SUBSTANCES NUTRITIVES
TRANSPORTE DE NUTRIENTES
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Summary:Phytochrome mediates chloroplast movement in the alga Mougeotia, possibly via changes in cytosolic calcium. It is known to regulate a calcium-activated potassium channel in the algal plasma membrane. As part of a characterization of the potassium channel, we examined the properties of calcium activation. The calcium ionophore A23187 activates the channel at external [Ca2+] as low as 20 micromolar. However, external [Ca2+] is not required for activation of the channel by photoactivated phytochrome. Furthermore, when an inhibitor of calcium release from internal stores, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate, hydrochloride (TMB-8), is present, red light no longer stimulates channel activity. We conclude that phytochrome activates the plasma membrane potassium channel by releasing calcium from intracellular calcium vesicles; the elevated cytosolic calcium then stimulates channel activity by an unknown mechanism. In the presence of TMB-8, red light does induce chloroplast rotation; thus, potassium channel activation may not be coupled to chloroplast rotation
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.92.3.831