First published online July 9, 2004; 10.1104/pp.104.041483
Plant Physiology 135:1398-1406 (2004)
© 2004 American Society of Plant Biologists
CELL BIOLOGY AND SIGNAL TRANSDUCTION
Identification and Characterization of Stretch-Activated Ion Channels in Pollen Protoplasts1
Rajiv Dutta and
Kenneth R. Robinson*
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907
Pollen tube growth requires a Ca2+ gradient, with elevated levels of cytosolic Ca2+ at the growing tip. This gradient's magnitude oscillates with growth oscillation but is always maintained. Ca2+ influx into the growing tip is necessary, and its magnitude also oscillates with growth. It has been widely assumed that stretch-activated Ca2+ channels underlie this influx, but such channels have never been reported in either pollen grains or pollen tubes. We have identified and characterized stretch-activated Ca2+ channels from Lilium longiflorum pollen grain and tube tip protoplasts. The channels were localized to a small region of the grain protoplasts associated with the site of tube germination. In addition, we find a stretch-activated K+ channel as well as a spontaneous K+ channel distributed over the entire grain surface, but neither was present at the germination site or at the tip. Neither stretch-activated channel was detected in the grain protoplasts unless the grains were left in germination medium for at least 1 h before protoplast preparation. The stretch-activated channels were inhibited by a spider venom that is known to block stretch-activated channels in animal cells, but the spontaneous channel was unaffected by the venom. The venom also stopped pollen tube germination and elongation and blocked Ca2+ entry into the growing tip, suggesting that channel function is necessary for growth.
1 This work was supported by the National Science Foundation (grant no. 0087517 IBN).
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.041483.
* Corresponding author; e-mail ken{at}video.bio.purdue.edu; fax 765–494–0876.
Received February 24, 2004;
returned for revision April 23, 2004;
accepted April 26, 2004.
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