Journal Article

Ca<sup>2+</sup> Influx into Lily Pollen Grains Through a Hyperpolarization-activated Ca<sup>2+</sup>-permeable Channel Which Can be Regulated by Extracellular CaM

Zhong-lin Shang, Li-geng Ma, Hai-lin Zhang, Rui-rong He, Xue-chen Wang, Su-juan Cui and Da-ye Sun

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 4, pages 598-608
Published in print April 2005 | ISSN: 0032-0781
Published online April 2005 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pci063
Ca2+ Influx into Lily Pollen Grains Through a Hyperpolarization-activated Ca2+-permeable Channel Which Can be Regulated by Extracellular CaM

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Confocal laser scanning microscopy (CLSM) and whole-cell patch-clamp were used to investigate the role of Ca2+ influx in maintaining the cytosolic Ca2+ concentration ([Ca2+]c) and the features of the Ca2+ influx pathway in germinating pollen grains of Lilium davidii D. [Ca2+]c decreased when Ca2+ influx was inhibited by EGTA or Ca2+ channel blockers. A hyperpolarization-activated Ca2+-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 [Ca2+]c decrease, while exogenous purified CaM triggers a transient increase of [Ca2+]c and also remarkably activated the hyperpolarization-activated Ca2+ conductance on plasma membrane of pollen protoplasts in a dose-dependent manner. Both the increase of [Ca2+]c and the activation of Ca2+ conductance which were induced by exogenous CaM were inhibited by EGTA or Ca2+ channel blockers. This primary evidence showed the presence of a voltage-dependent Ca2+-permeable channel, whose activity may be regulated by extracellular CaM, in pollen cells.

Keywords: Cytosolic calcium; Extracellular CaM; Hyperpolarization-activated Ca2+ permeable channel; Lilium davidii; Pollen grain; CaM, calmodulin; BSA, bovine serum albumin; BK solution, Brewbaker and Kwack’s solution; CLSM, confocal laser scanning microscopy; DTT, dithiothreitol; ECM, extracellular matrix; PDE, phosphodiesterase; HACC, hyperpolarization-activated calcium channel

Journal Article.  8374 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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