Structures of D14 and D14L in the strigolactone and karrikin signaling pathways

Megumi Kagiyama, Yoshinori Hirano, Tomoyuki Mori, Sun Yong Kim, Junko Kyozuka, Yoshiya Seto, Shinjiro Yamaguchi, Toshio Hakoshima

    Research output: Contribution to journalArticlepeer-review

    153 Citations (Scopus)

    Abstract

    Strigolactones (SLs) are plant hormones that inhibit shoot branching. DWARF14 (D14) inhibits rice tillering and is an SL receptor candidate in the branching inhibition pathway, whereas the close homologue DWARF14-LIKE (D14L) participates in the signaling pathway of karrikins (KARs), which are derived from burnt vegetation as smoke stimulants of seed germination. We provide the first evidence for direct binding of the bioactive SL analogue GR24 to D14. Isothermal titration calorimetry measurements show a D14-GR24 binding affinity in the sub-micromolar range. Similarly, bioactive KAR1 directly binds D14L in the micromolar range. The crystal structure of rice D14 shows a compact α-/β-fold hydrolase domain forming a deep ligand-binding pocket capable of accommodating GR24. Insertion of four α-helices between β6 strand and αD helix forms the helical cap of the pocket, although the pocket is open to the solvent. The pocket contains the conserved catalytic triad Ser-His-Asp aligned with the oxyanion hole, suggesting hydrolase activity. Although these structural characteristics are conserved in D14L, the D14L pocket is smaller than that of D14. The KAR-insensitive mutation kai2-1 is located at the prominent long β6-αD1 loop, which is characteristic in D14 and D14L, but not in related α-/β-fold hydrolases.

    Original languageEnglish
    Pages (from-to)147-160
    Number of pages14
    JournalGenes to Cells
    Volume18
    Issue number2
    DOIs
    Publication statusPublished - 2013 Feb

    ASJC Scopus subject areas

    • Genetics
    • Cell Biology

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