Isolation and functional characterization of an influx silicon transporter in two pumpkin cultivars contrasting in silicon accumulation

Namiki Mitani, Naoki Yamaji, Yukiko Ago, Kozo Iwasaki, Jian Feng Ma

    Research output: Contribution to journalArticlepeer-review

    114 Citations (Scopus)

    Abstract

    A high accumulation of silicon (Si) is required for overcoming abiotic and biotic stresses, but the molecular mechanisms of Si uptake, especially in dicotyledonous species, is poorly understood. Herein, we report the identification of an influx transporter of Si in two Cucurbita moschata (pumpkin) cultivars greatly differing in Si accumulation, which are used for the rootstocks of bloom and bloomless Cucumis sativus (cucumber), respectively. Heterogeneous expression in both Xenopus oocytes and rice mutant defective in Si uptake showed that the influx transporter from the bloom pumpkin rootstock can transport Si, whereas that from the bloomless rootstock cannot. Analysis with site-directed mutagenesis showed that, among the two amino acid residues differing between the two types of rootstocks, only changing a proline to a leucine at position 242 results in the loss of Si transport activity. Furthermore, all pumpkin cultivars for bloomless rootstocks tested have this mutation. The transporter is localized in all cells of the roots, and investigation of the subcellular localization with different approaches consistently showed that the influx Si transporter from the bloom pumpkin rootstock was localized at the plasma membrane, whereas the one from the bloomless rootstock was localized at the endoplasmic reticulum. Taken together, our results indicate that the difference in Si uptake between two pumpkin cultivars is probably the result of allelic variation in one amino acid residue of the Si influx transporter, which affects the subcellular localization and subsequent transport of Si from the external solution to the root cells.

    Original languageEnglish
    Pages (from-to)231-240
    Number of pages10
    JournalPlant Journal
    Volume66
    Issue number2
    DOIs
    Publication statusPublished - Apr 2011

    Keywords

    • bloom
    • cucumber
    • pumpkin
    • root stock
    • silicon
    • transporter

    ASJC Scopus subject areas

    • Genetics
    • Plant Science
    • Cell Biology

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