Destination-selective long-distance movement of phloem proteins

Koh Aoki, Nobuo Suzui, Shu Fujimaki, Naoshi Dohmae, Keiko Yonekura-Sakakibara, Toru Fujiwara, Hiroaki Hayashi, Tomoyuki Yamaya, Hitoshi Sakakibara

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    85 Citations (Scopus)


    The phloem macromolecular transport system plays a pivotal role in plant growth and development. However, little information is available regarding whether the long-distance trafficking of macromolecules is a controlled process or passive movement. Here, we demonstrate the destination-selective long-distance trafficking of phloem proteins. Direct introduction, into rice (Oryza sativa), of phloem proteins from pumpkin (Cucurbita maxima) was used to screen for the capacity of specific proteins to move long distance in rice sieve tubes. In our system, shoot-ward translocation appeared to be passively carried by bulk flow. By contrast, root-ward movement of the phloem RNA binding proteins 16-kD C. maxima phloem protein 1 (CmPP16-1) and CmPP16-2 was selectively controlled. When CmPP16 proteins were purified, the root-ward movement of CmPP16-1 became inefficient, suggesting the presence of pumpkin phloem factors that are responsible for determining protein destination. Gel-filtration chromatography and immunoprecipitation showed that CmPP16-1 formed a complex with other phloem sap proteins. These interacting proteins positively regulated the root-ward movement of CmPP16-1. The same proteins interacted with CmPP16-2 as well and did not positively regulate its root-ward movement. Our data demonstrate that, in addition to passive bulk flow transport, a destination-selective process is involved in long-distance movement control, and the selective movement is regulated by protein-protein interaction in the phloem sap.

    Original languageEnglish
    Pages (from-to)1801-1814
    Number of pages14
    JournalPlant Cell
    Issue number6
    Publication statusPublished - 2005

    ASJC Scopus subject areas

    • Plant Science
    • Cell Biology

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  • Cite this

    Aoki, K., Suzui, N., Fujimaki, S., Dohmae, N., Yonekura-Sakakibara, K., Fujiwara, T., Hayashi, H., Yamaya, T., & Sakakibara, H. (2005). Destination-selective long-distance movement of phloem proteins. Plant Cell, 17(6), 1801-1814.