A plant growth retardant, uniconazole, is a potent inhibitor of ABA catabolism in Arabidopsis

Shigeki Saito, Masanori Okamoto, Shoko Shinoda, Tetsuo Kushiro, Tomokazu Koshiba, Yuji Kamiya, Nobuhiro Hirai, Yasushi Todoroki, Kanzo Sakata, Eiji Nambara, Masaharu Mizutani

Research output: Contribution to journalArticlepeer-review

92 Citations (Scopus)


Plant growth retardants (PGRs) reduce the shoot growth of plants by inhibiting gibberellin biosynthesis. In this study, we performed detailed analyses of the inhibitory effects of PGRs on Arabidopsis abscisic acid (ABA) 8′-hydroxylase, a major ABA catabolic enzyme, recently identified as CYP707As. In an in vitro assay with CYP707A3 microsomes expressed in insect cells, uniconazole-P inhibited CYP707A3 activity more effectively than paclobutrazol or tetcyclacis, whereas the other PGRs tested did not inhibit it significantly. Uniconazole-P was found to be a strong competitive inhibitor (Ki = 8:0 nM) of ABA 8′-hydroxylase. Uniconazole-P-treated Arabidopsis plants showed enhanced drought tolerance. In uniconazole-P-treated plants, endogenous ABA levels increased 2-fold as compared with the control, and co-application of GA4 did not suppress the effects, indicating that the effects were not due to gibberellin deficiency. Thus uniconazole-P effectively inhibits ABA catabolism in Arabidopsis plants. We also discuss the structure-activity relationship of the azole-type compounds on ABA 8′-hydroxylase inhibitory activity.

Original languageEnglish
Pages (from-to)1731-1739
Number of pages9
JournalBioscience, Biotechnology and Biochemistry
Issue number7
Publication statusPublished - 2006


  • Abscisic acid
  • Cytochrome P450
  • Drought tolerance
  • Plant growth retardant
  • Uniconazole


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