Characterization of an inward rectifying cationic channel in onion guard cell vacuoles

Conference · Sat May 01 04:00:00 EDT 1993 · Plant Physiology; (United States)

OSTI ID:6221026

Amodeo, G; Zeiger, E; Escobar, A ^[1]

---

1. Univ. of California, Los Angeles (United States)

Ion channels modulate the large ion fluxes across the guard cell plasma membrane and tonoplast that are required for stomatal movement. In contrast to the well known ion channels at the plasma membrane, those at the guard cell tonoplast have not been described. We used patch clamping with guard cell protoplasts (GCP) from Allium cepa cotyledons to study channels from isolated tonoplast patches. The GCPs, obtained after a brief digestion time, released their vacuoles when exposed to an osmotic shock in the presence of EGTA. In inside-out patches bathed in symmetrical solutions (200 mM KCl as predominant ion) a 207[plus minus]1.6 pS channel was the most frequently observed. The channel was activated at negative potential and showed a very large rectification in the open probability in the absence of divalent cations in the vacuolar side. Replacement of monovalent ions in the bath solution gave a sequence of selectivity: Na[sup +]>K[sup +]>Rb[sup +]>Cs[sup +]. Both conduction and gating were investigated at the single channel level. Pulse protocols were achieved for the kinetic analysis of the activation and deactivation of the ionic channel. Records at different potentials were averaged to generate the ensemble profile of the macroscopic conductance. The analysis showed that this channel has at least one closed state and two open states. We suggest that this predominant inward rectifying cationic channel has an important role in the modulation of fluxes between the vacuole and cytosol of guard cells.

• OSTI ID: 6221026
• Report Number(s): CONF-9307119--
• Conference Information: Journal Name: Plant Physiology; (United States) Journal Volume: 102:1
• Country of Publication: United States
• Language: English

Related Subjects

550300* -- Cytology
59 BASIC BIOLOGICAL SCIENCES
ALLIUM CEPA
CATIONS
CELL CONSTITUENTS
CHARGED PARTICLES
FOOD
IONS
LILIOPSIDA
MAGNOLIOPHYTA
MEMBRANE TRANSPORT
MEMBRANES
ONIONS
OPENINGS
PLANTS
STOMATA
VEGETABLES