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First published online December 29, 2005; 10.1104/pp.105.068395 Plant Physiology 140:734-745 (2006) © 2006 American Society of Plant Biologists
Proteomics of Rac GTPase Signaling Reveals Its Predominant Role in Elicitor-Induced Defense Response of Cultured Rice Cells1,[W]Laboratory of Plant Molecular Genetics, Nara Institute of Science and Technology, Ikoma 630–0101, Japan (M.F., T.K., K.S.); and Agricultural and Veterinary Research Labs, Meiji Seika Kaisha, Sakado, Saitama 350–0289, Japan (K.U.)
We have previously shown that a human small GTPase Rac homolog, OsRac1, from rice (Oryza sativa) induces cascades of defense responses in rice plants and cultured cells. Sphingolipid elicitors (SEs) have been similarly shown to activate defense responses in rice. Therefore, to systematically analyze proteins whose expression levels are altered by OsRac1 and/or SE treatment, we performed a differential display analysis of proteins by the use of two-dimensional gel electrophoresis and mass spectrometry. A total of 271 proteins whose expression levels were altered by constitutively active (CA)-OsRac1 or SE were identified. Interestingly, of 100 proteins that were up-regulated by a SE, 87 were also induced by CA-OsRac1, suggesting that OsRac1 plays a pivotal role in defense responses induced by SE in cultured rice cells. In addition, CA-OsRac1 induces the expression of 119 proteins. Many proteins, such as pathogenesis-related proteins, SGT1, and prohibitin, which are known to be involved in the defense response, were found among these proteins. Proteins involved in redox regulation, chaperones such as heat shock proteins, BiP, and chaperonin 60, proteases and protease inhibitors, cytoskeletal proteins, subunits of proteasomes, and enzymes involved in the phenylpropanoid and ethylene biosynthesis pathways were found to be induced by CA-OsRac1 or SE. Results of our proteomic analysis revealed that OsRac1 is able to induce many proteins in various signaling and metabolic pathways and plays a predominant role in the defense response in cultured rice cells.
1 This work was supported by the Research for the Future Program of the Japan Society for Promotion of Science (JSPS; grant no. JSPS–RFTF 00L01604) and the Ministry of Agriculture, Forestry, and Fisheries of Japan, Rice Genome Project. 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: Ko Shimamoto (simamoto{at}bs.naist.jp). [W] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.068395. * Corresponding author; e-mail simamoto{at}bs.naist.jp; fax 81–743–72–5509. Received July 17, 2005; returned for revision November 9, 2005; accepted November 9, 2005. This article has been cited by other articles:
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