Calcium-regulated anion channels in the plasma membrane of Lilium longiflorum pollen protoplasts
Author for correspondence:
José Alberto Feijó
Tel: +351 214 407 941
- •Currents through anion channels in the plasma membrane of Lilium longiflorum pollen grain protoplasts were studied under conditions of symmetrical anionic concentrations by means of patch-clamp whole-cell configuration.
- •With Cl−-based intra- and extracellular solutions, three outward-rectifying anion conductances, ICl1, ICl2 and ICl3, were identified. These three activities were discriminated by differential rundown behaviour and sensitivity to 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), which could not be attributed to one or more channel types. All shared strong outward rectification, activated instantaneously and displayed a slow time-dependent activation for positive potentials. All showed modulation by intracellular calcium ([Ca2+]in), increasing intensity from 6.04 nM up to 0.5 mM (ICl1), or reaching a maximum value with 8.50 μM (ICl2 and ICl3).
- •After rundown, the anionic currents measured using NO3−-based solutions were indistinguishable, indicating that the permeabilities of the channels for Cl− and NO3− are similar. Additionally, unitary anionic currents were measured from outside-out excised patches, confirming the presence of individual anionic channels.
- •This study shows for the first time the presence of a large anionic conductance across the membrane of pollen protoplasts, resulting from the presence of Ca2+-regulated channels. A similar conductance was also found in germinated pollen. We hypothesize that these putative channels may be responsible for the large anionic fluxes previously detected by means of self-referencing vibrating probes.