Ca2+ influx into lily pollen grains through a hyperpolarization-activated Ca2+-permeable channel which can be regulated by extracellular CaM

• Published in: Plant and cell physiology 2005-04, Vol.46 (4), p.598-608
• Main Authors: Shang, Z.L.(Hebei Normal Univ., Shijiazhuang (China)), Ma, L.G, Zhang, H.L, He, R.R, Wang, X.C, Cui, S.J, Sun, D.Y
• Format: Article
• Language: English
• Subjects: Antibodies; BK solution; bovine serum albumin; Brewbaker and Kwack’s solution; BSA; CALCIO; CALCIUM; Calcium - metabolism; Calcium Channel Blockers - pharmacology; calcium channels; Calcium Channels - physiology; Calcium Signaling - physiology; CALMODULIN; Calmodulin - immunology; Calmodulin - metabolism; Calmodulin - pharmacology; CALMODULINA; CALMODULINE; CaM; CARDIOVASCULAR AGENTS; Cell Membrane - physiology; Chelating Agents - pharmacology; CLSM; confocal laser scanning microscopy; Cytosol - metabolism; Cytosolic calcium; dithiothreitol; DTT; ECM; Egtazic Acid - pharmacology; electrophysiology; ethylene glycol tetraacetic acid; Extracellular CaM; extracellular matrix; Extracellular Space - metabolism; HACC; Hyperpolarization-activated Ca2+ permeable channel; hyperpolarization-activated calcium channel; LILIUM; Lilium - growth & development; Lilium - physiology; Lilium davidii; MEDICAMENTOS CARDIOVASCULARES; Membrane Potentials - drug effects; Membrane Potentials - physiology; MODIFICATEUR CARDIOVASCULAIRE; patch-clamp techniques; PDE; phosphodiesterase; plant physiology; plasma membrane; POLEN; POLLEN; Pollen - physiology; pollen germination; Pollen grain; protoplasts; Signal Transduction - physiology
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/pcp/pci063

Confocal laser scanning microscopy (CLSM) and whole cell patch-clamp were used to investigate the role of Ca(2+) influx in maintaining the cytosolic Ca(2+) concentration ([Ca(2+)]c) and the features of the Ca(2+) influx pathway in germinating pollen grains of Lilium davidii D. [Ca(2+)]c, decreased when Ca(2+) influx was inhibited by EGTA or Ca(2+) channel blockers. A hyperpolarization-activated Ca(2+) permeable channel, which can be suppressed by trivalent cations, verapamil, nifedipine or diltiazem, was identified on the plasma membrane of pollen protoplasts with whole cell patch-clamp recording. Calmodulin (CaM) antiserum and W7-agarose, both of which are cell-impermeable CaM antagonists, lead to a [Ca(2+)]c, decrease, while exogenous purified CaM triggers a transient increase of [Ca(2+)]c and also remarkably activated the hyperpolarization-activated Ca(2+) conductance on plasma membrane of pollen protoplasts in a dose-dependent manner. Both the increase of [Ca(2+)]c and the activation of Ca(2+) conductance which were induced by exogenous CaM were inhibited by EGTA or Ca(2+) channel blockers. This primary evidence showed the presence of a voltage-dependent Ca(2+)-permeable channel, whose activity may be regulated by extracellular CaM, in pollen cells.