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First published online March 9, 2007; 10.1104/pp.107.096131 Plant Physiology 144:94-104 (2007) © 2007 American Society of Plant Biologists OPEN ACCESS ARTICLE
Nitric Oxide and cGMP Signaling in Calcium-Dependent Development of Cell Polarity in Ceratopteris richardii[W],[OA]Section of Molecular Cell and Developmental Biology, University of Texas, Austin, Texas 78712 (M.L.S., S.J.R.); Department of Biological Sciences, University of Missouri, Rolla, Missouri 65409 (K.E.M.); and Department of Agricultural and Biological Engineering and Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 479072093 (D.M.P.)
Single-celled spores of the fern Ceratopteris richardii undergo gravity-directed cell polarity development that is driven by polar calcium currents. Here we present results that establish a role for nitric oxide (NO)/cGMP signaling in transducing the stimulus of gravity to directed polarization of the spores. Application of specific NO donors and scavengers inhibited the calcium-dependent gravity response in a dose-dependent manner. The effects of NO donor exposure were antagonized by application of NO scavenger compounds. Similarly, the guanylate cyclase inhibitors 6-anilino-5,8-quinolinedione and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin, and the phosphodiesterase inhibitor Viagra, which modulate NO-dependent cGMP levels in the cells, disrupted gravity-directed cell polarity in a dose-dependent manner. Viagra effects were antagonized by application of NO scavengers, consistent with the postulate that NO and cGMP are linked in the signaling pathway. To identify other components of the signaling system we analyzed gene expression changes induced by Viagra treatment using microarrays and quantitative real-time reverse transcription-polymerase chain reaction. Preliminary microarray analysis revealed several genes whose expression was significantly altered by Viagra treatment. Three of these genes had strong sequence similarity to key signal transduction or stress response genes and quantitative real-time reverse transcription-polymerase chain reaction was used to more rigorously quantify the effects of Viagra on their expression in spores and to test how closely these effects could be mimicked by treatment with dibutyryl cGMP. Taken together our results implicate NO and cGMP as downstream effectors that help link the gravity stimulus to polarized growth in C. richardii spores.
The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: D. Marshall Porterfield (porterf{at}purdue.edu). [W] The online version of this article contains Web-only data. [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.107.096131 * Corresponding author; e-mail porterf{at}purdue.edu; fax 7654961115. Received January 18, 2007; accepted February 27, 2007; published March 9, 2007. Related articles in Plant Physiol.:
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