title: cAMP activates hyperpolarization-activated Ca2+ channels in the pollen of Pyrus pyrifolia.
abstract: Many signal-transduction processes in plant cells have been suggested to be triggered by signal-induced opening of calcium ion (Ca(2+)) channels in the plasma membrane. Cyclic nucleotides have been proposed to lead to an increase in cytosolic free Ca(2+) in pollen. However, direct recordings of cyclic-nucleotide-induced Ca(2+) currents in pollen have not yet been obtained. Here, we report that cyclic AMP (cAMP) activated a hyperpolarization-activated Ca(2+) channel in the Pyrus pyrifolia pollen tube using the patch-clamp technique, which resulted in a significant increase in pollen tube protoplast cytosolic-Ca(2+) concentration. Outside-out single channel configuration identified that cAMP directly increased the Ca(2+) channel open-probability without affecting channel conductance. cAMP-induced currents were composed of both Ca(2+) and K(+). However, cGMP failed to mimic the cAMP effect. Higher cytosolic free-Ca(2+) concentration significantly decreased the cAMP-induced currents. These results provide direct evidence for cAMP activation of hyperpolarization-activated Ca(2+) channels in the plasma membrane of pollen tubes, which, in turn, modulate cellular responses in regulation of pollen tube growth.
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, No. 6 Tongwei Road, Nanjing, China.
authors.forename: Juyou
authors.initials: J
authors.lastname: Wu
authors.forename: Haiyong
authors.initials: H
authors.lastname: Qu
authors.forename: Cong
authors.initials: C
authors.lastname: Jin
authors.forename: Zhongling
authors.initials: Z
authors.lastname: Shang
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.forename: Guohua
authors.initials: G
authors.lastname: Xu
authors.forename: Yongbing
authors.initials: Y
authors.lastname: Gao
authors.forename: Shaoling
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000496:Alloxan / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability; D016764:Cell Polarity; D000242:Cyclic AMP / Q000378:metabolism*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D053205:Pollen Tube / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D031989:Pyrus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D000496:Alloxan; D000242:Cyclic AMP; D002118:Calcium