Role of the phytochrome and cryptochrome signaling pathways in hypocotyl phototropism

Tomoko Tsuchida-Mayama, Tatsuya Sakai, Atsushi Hanada, Yukiko Uehara, Tadao Asami, Shinjiro Yamaguchi

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    57 Citations (Scopus)


    Unilateral blue-light irradiation activates phototropin (phot) photoreceptors, resulting in asymmetric distribution of the phytohormone auxin and induction of a phototropic response in higher plants. Other photoreceptors, including phytochrome (phy) and cryptochrome (cry), have been proposed as modulators of phototropic responses. We show here that either phy or cry is required for hypocotyl phototropism in Arabidopsis thaliana under high fluence rates of blue light, and that constitutive expression of ROOT PHOTOTROPISM 2 (RPT2) and treatment with the phytohormone gibberellin (GA) biosynthesis inhibitor paclobutrazol partially and independently complement the non-phototropic hypocotyl phenotype of the phyA cry1 cry2 mutant under high fluence rates of blue light. Our results indicate that induction of RPT2 and reduction in the GA are crucial for hypocotyl phototropic regulation by phy and cry. We also show that GA suppresses hypocotyl bending via destabilization of DELLA transcriptional regulators under darkness, but does not suppress the phototropic response in the presence of either phyA or cryptochromes, suggesting that these photoreceptors control not only the GA content but also the GA sensing and/or signaling that affects hypocotyl phototropism. The metabolic and signaling regulation of not only auxin but also GA by photoreceptors therefore appears to determine the hypocotyl growth pattern, including phototropic and gravitropic responses and inhibition of hypocotyl elongation, for adaptation to various light environments.

    Original languageEnglish
    Pages (from-to)653-662
    Number of pages10
    JournalPlant Journal
    Issue number4
    Publication statusPublished - 2010 May


    • Cryptochrome
    • DELLA
    • Gibberellin
    • Phototropism
    • Phytochrome
    • RPT2

    ASJC Scopus subject areas

    • Genetics
    • Plant Science
    • Cell Biology


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