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

Michitaka Notaguchi, Shmuel Wolf, William J. Lucas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

108 Scopus citations


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.

Original languageAmerican English
Pages (from-to)760-772
Number of pages13
JournalJournal of Integrative Plant Biology
Issue number10
StatePublished - Oct 2012


  • Arabidopsis
  • Grafting
  • Lateral root development
  • Phloem-mobile transcript


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