P-Chlorophenoxyisobutyric acid impairs auxin response for gravity-regulated peg formation in cucumber (Cucumis sativus) seedlings

Minobu Shimizu, Yutaka Miyazawa, Nobuharu Fujii, Hideyuki Takahashi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Cucumber (Cucumis sativus L.) seedlings form a specialized protuberance, the peg, on the transition zone between the hypocotyl and the root. When cucumber seeds germinate in a horizontal position, the seedlings develop a peg on the lower side of the transition zone. To verify the role of auxin action in peg formation, we examined the effect of the anti-auxin, p- chlorophenoxyisobutyric acid (PCIB), on peg formation and mRNA accumulation of auxin-regulated genes. Application of PCIB to cucumber seedlings inhibited peg formation. The application of indole-3-acetic acid (IAA) competed with PCIB and induced peg formation. Furthermore, application of PCIB decreased auxin-inducible CsIAA1 mRNA and increased auxin-repressible CsGRP1 mRNA in the lower side of the transition zone. The differential accumulation of CsIAA1 and CsGRP1 mRNAs in the transition zone of cucumber seedlings grown in a horizontal position was smaller in the PCIB-treated seedlings. These results demonstrate that endogenous auxin redistributes and induces the differential expression of auxin-regulated genes, and ultimately results in the suppression or induction of peg formation in the gravistimulated transition zone of cucumber seedlings.

Original languageEnglish
Pages (from-to)107-114
Number of pages8
JournalJournal of Plant Research
Issue number1
Publication statusPublished - 2008 Jan


  • Auxin
  • Cucumis sativus
  • Gravitropism
  • Gravity
  • PCIB
  • Peg

ASJC Scopus subject areas

  • Plant Science


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