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First published online January 4, 2008; 10.1104/pp.107.113647 Plant Physiology 146:1098-1108 (2008) © 2008 American Society of Plant Biologists OPEN ACCESS ARTICLE
Myosin XI-K Is Required for Rapid Trafficking of Golgi Stacks, Peroxisomes, and Mitochondria in Leaf Cells of Nicotiana benthamiana1,[W],[OA]Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon 97331 (D.A., A.I.P., V.V.P., V.V.D.); and National Center for Biotechnology Information, National Institutes of Health, Bethesda, Maryland 20894 (K.S.M., E.V.K.)
A prominent feature of plant cells is the rapid, incessant movement of the organelles traditionally defined as cytoplasmic streaming and attributed to actomyosin motility. We sequenced six complete Nicotiana benthamiana cDNAs that encode class XI and class VIII myosins. Phylogenetic analysis indicates that these two classes of myosins diverged prior to the radiation of green algae and land plants from a common ancestor and that the common ancestor of land plants likely possessed at least seven myosins. We further report here that movement of Golgi stacks, mitochondria, and peroxisomes in the leaf cells of N. benthamiana is mediated mainly by myosin XI-K. Suppression of myosin XI-K function using dominant negative inhibition or RNA interference dramatically reduced movement of each of these organelles. When similar approaches were used to inhibit functions of myosin XI-2 or XI-F, only moderate to marginal effects were observed. Organelle trafficking was virtually unaffected in response to inhibition of each of the three class VIII myosins. Interestingly, none of the tested six myosins appears to be involved in light-induced movements of chloroplasts. Taken together, these data strongly suggest that myosin XI-K has a major role in trafficking of Golgi stacks, mitochondria, and peroxisomes, whereas myosins XI-2 and XI-F might perform accessory functions in this process. In addition, our analysis of thousands of individual organelles revealed independent movement patterns for Golgi stacks, mitochondria, and peroxisomes, indicating that the notion of coordinated cytoplasmic streaming is not generally applicable to higher plants.
1 This work was supported in part by the National Institutes of Health (grant no. GM053190 to V.V.D.) and by the Vaadia/U.S.-Israel Binational Agricultural Research and Development Fund (postdoctoral fellowship award no. F1–354–2004 to D.A.). 2 These authors contributed equally to the article. 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: Valerian V. Dolja (doljav{at}science.oregonstate.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.107.113647 * Corresponding author; e-mail doljav{at}science.oregonstate.edu. Received November 27, 2007; accepted December 24, 2007; published January 4, 2008. Related articles in Plant Physiol.:
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