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

• Published in: Bioscience, biotechnology, and biochemistry Vol. 70; no. 7; pp. 1731 - 1739
• Main Authors: Saito, S.(Kyoto Univ. (Japan)), Okamoto, M, Shinoda, S, Kushiro, T, Koshiba, T, Kamiya, Y, Hirai, N, Todoroki, Y, Sakata, K, Nambara, E, Mizutani, M
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Society for Bioscience, Biotechnology, and Agrochemistry 01.07.2006; Japan Society for Bioscience Biotechnology and Agrochemistry; Oxford University Press
• Subjects: ABA; abscisic acid; Abscisic Acid - metabolism; ARABIDOPSIS; Arabidopsis - drug effects; Arabidopsis - metabolism; Arabidopsis Proteins - antagonists & inhibitors; Biological and medical sciences; biosynthesis; biotechnology; CATABOLISM; CATABOLISME; CATABOLISMO; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; cytochrome P450; DROUGHT RESISTANCE; drought tolerance; enzymes; Fundamental and applied biological sciences. Psychology; gibberellins; INHIBICION; INHIBITION; insects; microsomes; Microsomes - drug effects; Microsomes - metabolism; Mixed Function Oxygenases - antagonists & inhibitors; paclobutrazol; plant growth; plant growth inhibitors; Plant Growth Regulators - pharmacology; plant growth retardant; RESISTANCE A LA SECHERESSE; RESISTENCIA A LA SEQUIA; structure-activity relationships; Triazoles - pharmacology; UNICONAZOL; UNICONAZOLE; plant growth retardant; Arabidopsis; Growth; Cytochrome P450; Tolerance; uniconazole; Cruciferae; Dicotyledones; Angiospermae; Abscisic acid; drought tolerance; Spermatophyta; Catabolism; Inhibitor; Drought
• ISSN: 0916-8451; 1347-6947; 1347-6947
• DOI: 10.1271/bbb.60077

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 (Ksub(i)=8.0nM) 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 GAsub(4) 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.