SOMNUS, a CCCH-type zinc finger protein in Arabidopsis, negatively regulates light-dependent seed germination downstream of PIL5

Hwan Kim Dong, Shinjiro Yamaguchi, Soohwan Lim, Eunkyoo Oh, Jeongmu Park, Atsushi Hanada, Yuji Kamiya, Giltsu Choi

    Research output: Contribution to journalArticle

    177 Citations (Scopus)

    Abstract

    Light absorbed by seed phytochromes of Arabidopsis thaliana modulates abscisic acid (ABA) and gibberellic acid (GA) signaling pathways at least partly via PHYTOCHROME-INTERACTING FACTOR3-LIKE5 (PIL5), a phytochrome-interacting basic helix-loop-helix transcription factor. Here, we report a new mutant, somnus (som), that germinates in darkness, independently of various light regimens. SOM encodes a nucleus-localized CCCH-type zinc finger protein. The som mutant has lower levels of ABA and elevated levels of GA due to expressional changes in ABA and GA metabolic genes. Unlike PIL5, however, SOM does not regulate the expression of GA-INSENSITIVE and REPRESSOR OF GA1 (RGA/RGA1), two DELLA genes encoding GA negative signaling components. Our in vivo analysis shows that PIL5 activates the expression of SOM by binding directly to its promoter, suggesting that PIL5 regulates ABA and GA metabolic genes partly through SOM. In agreement with these results, we also observed that the reduced germination frequency of a PIL5 overexpression line is rescued by the som mutation and that this rescue is accompanied by expressional changes in ABA and GA metabolic genes. Taken together, our results indicate that SOM is a component in the phytochrome signal transduction pathway that regulates hormone metabolic genes downstream of PIL5 during seed germination.

    Original languageEnglish
    Pages (from-to)1260-1277
    Number of pages18
    JournalPlant Cell
    Volume20
    Issue number5
    DOIs
    Publication statusPublished - 2008 May 1

    ASJC Scopus subject areas

    • Plant Science
    • Cell Biology

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  • Cite this

    Dong, H. K., Yamaguchi, S., Lim, S., Oh, E., Park, J., Hanada, A., Kamiya, Y., & Choi, G. (2008). SOMNUS, a CCCH-type zinc finger protein in Arabidopsis, negatively regulates light-dependent seed germination downstream of PIL5. Plant Cell, 20(5), 1260-1277. https://doi.org/10.1105/tpc.108.058859