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

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 t...

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Bibliographic Details
Published in:Journal of integrative plant biology 2012-10, Vol.54 (10), p.760-772
Main Authors: Notaguchi, Michitaka, Wolf, Shmuel, Lucas, William J.
Format: Article
Language:English
Subjects:
Arabidopsis
Arabidopsis - genetics
Arabidopsis - growth & development
Arabidopsis Proteins - genetics
AUX/IAA
grafting
lateral root development
Meristem - metabolism
Phloem - metabolism
phloem-mobile transcript
Plant Roots - growth & development
Plant Roots - metabolism
Transcription Factors - genetics
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Summary: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.
ISSN:1672-9072
1744-7909
DOI:10.1111/j.1744-7909.2012.01155.x