The SAC51 family plays a central role in thermospermine responses in arabidopsis

Qingqing Cai, Hiroko Fukushima, Mai Yamamoto, Nami Ishii, Tomoaki Sakamoto, Tetsuya Kurata, Hiroyasu Motose, Taku Takahashi

    Research output: Contribution to journalArticle

    19 Citations (Scopus)

    Abstract

    The acaulis5 (acl5) mutant of Arabidopsis thaliana is defective in the biosynthesis of thermospermine and shows a dwarf phenotype associated with excess xylem differentiation. SAC51 was identified from a dominant suppressor of acl5, sac51-d, and encodes a basic helix-loop-helix protein. The sac51-d mutant has a premature termination codon in an upstream open reading frame (uORF) that is conserved among all four members of the SAC51 family, SAC51 and SACL1-SACL3. This suggests that thermospermine cancels the inhibitory effect of the uORF in main ORF translation. Another suppressor, sac57-d, has a mutation in the conserved uORF of SACL3. To define further the function of the SAC51 family in the thermospermine response, we analyzed T-DNA insertion mutants of each gene. Although sacl1-1 may not be a null allele, the quadruple mutant showed a semi-dwarf phenotype but with an increased level of thermospermine and decreased sensitivity to exogenous thermospermine that normally represses xylem differentiation. The sac51-1 sacl3-1 double mutant was also insensitive to thermospermine. These results suggest that SAC51 and SACL3 play a key role in thermospermine-dependent negative control of thermospermine biosynthesis and xylem differentiation. Using 5' leader-GUS (b-glucuronidase) fusion constructs, however, we detected a significant enhancement of the GUS activity by thermospermine only in SAC51 and SACL1 constructs. Furthermore, while acl5-1 sac51-1 showed the acl5 dwarf phenotype, acl5-1 sacl3-1 exhibited an extremely tiny-plant phenotype. These results suggest a complex regulatory network for the thermospermine response in which SAC51 and SACL3 function in parallel pathways.

    Original languageEnglish
    Pages (from-to)1583-1592
    Number of pages10
    JournalPlant and Cell Physiology
    Volume57
    Issue number8
    DOIs
    Publication statusPublished - 2016 Aug 1

    Keywords

    • Arabidopsis
    • Thermospermine
    • Translation
    • Xylem differentiation
    • uORF

    ASJC Scopus subject areas

    • Physiology
    • Plant Science
    • Cell Biology

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  • Cite this

    Cai, Q., Fukushima, H., Yamamoto, M., Ishii, N., Sakamoto, T., Kurata, T., Motose, H., & Takahashi, T. (2016). The SAC51 family plays a central role in thermospermine responses in arabidopsis. Plant and Cell Physiology, 57(8), 1583-1592. https://doi.org/10.1093/pcp/pcw113