| NATURE • VOL 338 • 30 MARCH
1989 • PP 427-430 |
|
Cytosolic calcium regulates ion channels in the plasma membrane
of Vicia faba guard cells
Julian I. Schroeder & Susumu Hagiwara Department of Physiology, Jerry Lewis Neuromuscular Research Center UCLA School of Medicine, Los Angeles, California 90024, USA |
| The molecular mechanisms by which Ca2+
controls a variety of ion transport-associated cellular functions in higher
plant cells, including movements of stomatal pores, remain unknown. Stomatal
pores regulate the gas exchange in leaves. Openings of stomatal pores are
mediated by an increase in the intracellular potassium and anion content
of guard cells. Voltage-dependent K+ channels and hyperpolarizing H+ pumps
have been identified as mechanisms controlling stomatal movements. But depolarizing
mechanisms required for K+ efflux during stomatal closing remain unknown.
Indirect evidence suggests that Ca2+ triggers stomatal closing and inhibits
stomatal opening. Using patch-clamp techniques, we show here that elevated
(micromolar) concentrations of cytosolic Ca2+ in guard cells block inward
rectifying K+ channels. Furthermore, elevation of cytosolic Ca2+ leads to
the activation of a voltage-dependent depolarizing conductance with a permeability
to anions. The Ca2+ induced modulation of ion channels reported here could
provide a molecular basis for Ca2+ dependent regulation of stomatal movements
in leaves. |