Chemical regulation of abscisic acid catabolism in plants by cytochrome P450 inhibitors.
Plant hormone abscisic acid (ABA) is an important factor for conferring drought stress resistance on plants. Therefore, small molecules that regulate ABA levels in plants can be useful both for investigating functions of ABA and for developing new plant growth regulators. Abscisic acid (ABA) catabolism in plants is primarily regulated by ABA 8'-hydroxylase, which is a cytochrome P450 (P450). We tested known P450 inhibitors containing a triazole group and found that uniconazole-P inhibited ABA catabolism in cultured tobacco Bright Yellow-2 cells. In a structure-activity study of uniconazole, we found a more effective ABA catabolic inhibitor (diniconazole) than uniconazole-P. Diniconazole, a fungicide, acted as a potent competitive inhibitor of recombinant Arabidopsis ABA 8'-hydroxylase, CYP707A3, in an in vitro assay. Diniconazole-treated plants retained a higher ABA content and higher transcription levels of ABA response genes during rehydration than did untreated plants and were more drought stress tolerant than untreated plants. These results strongly suggest that ABA catabolic inhibitors that target ABA 8'-hydroxylase can regulate the ABA content of plants and conferred drought stress resistance on plants. The optical resolution of diniconazole revealed that the S-form isomer, which is a weak fungicidal isomer, was more active as an ABA catabolic inhibitor than was the R-form isomer.
Kitahata
Nobutaka
N
Plant Functions Laboratory, RIKEN, Saitama 351-0198, Japan; Department of Biological and Environmental Sciences, Saitama University, Saitama 338-8570, Japan.
Saito
Shigeki
S
Miyazawa
Yutaka
Y
Umezawa
Taishi
T
Shimada
Yukihisa
Y
Min
Yong Ki
YK
Mizutani
Masaharu
M
Hirai
Nobuhiro
N
Shinozaki
Kazuo
K
Yoshida
Shigeo
S
Asami
Tadao
T
D000040:Abscisic Acid / Q000378:metabolism*; D001483:Base Sequence; D065607:Cytochrome P-450 Enzyme Inhibitors; D017931:DNA Primers; D004190:Disasters; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D010944:Plants / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013329:Structure-Activity Relationship; D014230:Triazoles / Q000494:pharmacology
D065607:Cytochrome P-450 Enzyme Inhibitors; D017931:DNA Primers; D004791:Enzyme Inhibitors; D014230:Triazoles; D000040:Abscisic Acid; C049346:diniconazole