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First published online March 4, 2009; 10.1104/pp.108.134767 Plant Physiology 150:378-387 (2009) © 2009 American Society of Plant Biologists OPEN ACCESS ARTICLE
The Phloem-Delivered RNA Pool Contains Small Noncoding RNAs and Interferes with Translation1,[W],[OA]Department of Biochemistry, Max F. Perutz Laboratories, University of Vienna, Vienna, A–1030, Austria
In plants, the vascular tissue contains the enucleated sieve tubes facilitating long-distance transport of nutrients, hormones, and proteins. In addition, several mRNAs and small interfering RNAs/microRNAs were shown to be delivered via sieve tubes whose content is embodied by the phloem sap (PS). A number of these phloem transcripts are transported from source to sink tissues and function at targeted tissues. To gain additional insights into phloem-delivered RNAs and their potential role in signaling, we isolated and characterized PS RNA molecules distinct from microRNAs/small interfering RNAs with a size ranging from 30 to 90 bases. We detected a high number of full-length and phloem-specific fragments of noncoding RNAs such as tRNAs, ribosomal RNAs, and spliceosomal RNAs in the PS of pumpkin (Cucurbita maxima). In vitro assays show that small quantities of PS RNA molecules efficiently inhibit translation in an unspecific manner. Proof of concept that PS-specific tRNA fragments may interfere with ribosomal activity was obtained with artificially produced tRNA fragments. The results are discussed in terms of a functional role for long distance delivered noncoding PS RNAs.
1 This work was supported by the Austrian Science Fund (grant no. P19682–B03 to F.K.). The author responsible for the 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: Friedrich Kragler (friedrich.kragler{at}univie.ac.at). [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.108.134767 * Corresponding author; e-mail friedrich.kragler{at}univie.ac.at. Received December 23, 2008; accepted March 1, 2009; published March 4, 2009. This article has been cited by other articles:
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