ACAULIS5, an Arabidopsis gene required for stem elongation, encodes a spermine synthase

Yoshie Hanzawa, Taku Takahashi, Anthony J. Michael, Daniel Burtin, Deborah Long, Manuel Pineiro, George Coupland, Yoshibumi Komeda

Research output: Contribution to journalArticlepeer-review

233 Scopus citations


Polyamines have been implicated in a wide range of biological processes, including growth and development in bacteria and animals, but their function in higher plants is unclear. Here we show that the Aribidopsis ACAULIS5 (ACL5) gene, whose inactivation causes a defect in the elongation of stem internodes by reducing cell expansion, encodes a protein that shares sequence similarity with the polyamine biosynthetic enzymes spermidine synthase and spermine synthase. Expression of the recombinant ACL5 protein in Escherichia coli showed that ACL5 possesses spermine synthase activity. Restoration of the acl5 mutant phenotype by somatic reversion of a transposon-induced allele suggests a non-cell-autonomous function for the ACL5 gene product. We also found that expression of the ACL5 cDNA under the control of a heat shock gene promoter in acl5 mutant plants restores the phenotype in a heat shock-dependent manner. The results of the experiments showed that polyamines play an essential role in promotion of internode elongation through cell expansion in Arabidopsis. We discuss the relationships to plant growth regulators such as auxin and gibberellins that have related functions.

Original languageEnglish (US)
Pages (from-to)4248-4256
Number of pages9
JournalEMBO Journal
Issue number16
StatePublished - Aug 15 2000


  • Arabidopsis
  • Internode elongation
  • Polyamines
  • Spermine

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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