title: Calcium-regulated anion channels in the plasma membrane of Lilium longiflorum pollen protoplasts.
abstract: • 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, I(Cl1) , I(Cl2) and I(Cl3) , 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 ([Ca(2+) ](in) ), increasing intensity from 6.04 nM up to 0.5 mM (I(Cl1) ), or reaching a maximum value with 8.50 μM (I(Cl2) and I(Cl3) ). • After rundown, the anionic currents measured using NO(3) (-) -based solutions were indistinguishable, indicating that the permeabilities of the channels for Cl(-) and NO(3) (-) 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 Ca(2+) -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.
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.|Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal.|Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Tavares
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.|Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal.|Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal.
authors.forename: Pedro Nuno
authors.initials: PN
authors.lastname: Dias
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.|Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal.|Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Domingos
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: Teresa Fonseca
authors.initials: TF
authors.lastname: Moura
authors.affiliation: Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal.|Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, C2, 1749-016 Lisboa, Portugal.
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Feijó
authors.affiliation: REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.|Instituto Gulbenkian de Ciência, Oeiras, 2780-156 Oeiras, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Bicho
mesh_terms: D000838:Anions / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002712:Chlorides / Q000494:pharmacology; D018525:Germination / Q000187:drug effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D027762:Lilium / Q000166:cytology*; D008564:Membrane Potentials / Q000187:drug effects; D009566:Nitrates / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D011058:Pollen / Q000187:drug effects / Q000378:metabolism*; D011523:Protoplasts / Q000166:cytology*; D014867:Water
chemical_list: D000838:Anions; D002712:Chlorides; D007473:Ion Channels; D009566:Nitrates; D009579:Nitrobenzoates; D014867:Water; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D002118:Calcium