J Integr Plant Biol. ›› 2012, Vol. 54 ›› Issue (10): 760-772.DOI: 10.1111/j.1744-7909.2012.01155.x

• Research Articles • Previous Articles     Next Articles

Phloem-Mobile Aux/IAA Transcripts Target to the Root Tip and Modify Root Architecture

Michitaka Notaguchi1†, Shmuel Wolf2 and William J. Lucas1*   

  1. 1Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA
    2The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture and the Otto Warburg Minerva Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, The Robert H. Smith Faculty of Agriculture, Food and Environment, Rehovot 76100, Israel
  • Received:2012-07-22 Accepted:2012-08-20 Published:2012-10-01
  • About author:Current address: JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
    *Corresponding author Tel: +1 530 752 1093; Fax: +1 530 752 5410; E-mail: wjlucas@ucdavis.edu

Abstract:

In plants, the phloem is the component of the vascular system that delivers nutrients and transmits signals from mature leaves to developing sink tissues. Recent studies have identified proteins, mRNA, and small RNA within the phloem sap of several plant species. It is now of considerable interest to elucidate the biological functions of these potential long-distance signal agents, to further our understanding of how plants coordinate their developmental programs at the whole-plant level. In this study, we developed a strategy for the functional analysis of phloem-mobile mRNA by focusing on IAA transcripts, whose mobility has previously been reported in melon (Cucumis melo cv. Hale's Best Jumbo). Indoleacetic acid (IAA) proteins are key transcriptional regulators of auxin signaling, and are involved in a broad range of developmental processes including root development. We used a combination of vasculature-enriched sampling and hetero-grafting techniques to identify IAA18 and IAA28 as phloem-mobile transcripts in the model plant Arabidopsis thaliana. Micro-grafting experiments were used to confirm that these IAA transcripts, which are generated in vascular tissues of mature leaves, are then transported into the root system where they negatively regulate lateral root formation. Based on these findings, we present a model in which auxin distribution, in combination with phloem-mobile Aux/IAA transcripts, can determine the sites of auxin action.

Notaguchi M, Wolf S, Lucas WJ (2012) Phloem-mobile Aux/IAA transcripts target to the root tip and modify root architecture. J. Integr. Plant Biol. 54(10), 760–772.

Key words: Phloem-mobile transcript, aux/IAA, lateral root development, grafting, Arabidopsis

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