Dehydration tolerance in apple seedlings is affected by an inhibitor of ABA 8'-hydroxylase CYP707A.
The effects of an abscisic acid (ABA) 8'-hydroxylase inhibitor (Abz-F1) on ABA catabolism, stomatal aperture, and water potential were examined in apple seedlings under dehydration and rehydration conditions. In this study, 9-cis-epoxycarotenoid dioxigenase (MdNCED) and ABA 8'-hydroxylase (MdCYP707A) genes were isolated and their expressions were investigated under dehydration and rehydration conditions. The stomatal aperture decreased up to 4 h after spraying with Abz-F1 and the stomatal aperture in the Abz-F1-treated leaves was generally lower than that in the untreated control-leaves during the dehydration condition. Although the water potential in untreated control-leaves decreased with the progress of dehydration, it was maintained at a higher level in the Abz-F1 treated-leaves than in the untreated control-leaves during dehydration. Endogenous ABA concentrations increased with dehydration in both the Abz-F1 treated- and untreated-control-leaves, but the ABA levels in the Abz-F1 treated-leaves were higher than those in the untreated control-leaves throughout dehydration. In contrast, the phaseic acid (PA) concentrations in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves during dehydration. The expressions of MdNCEDs in the Abz-F1 treated-leaves were lower than those in the untreated control-leaves regardless of the higher endogenous ABA concentrations. Moreover, the expressions of MdCYP707As in the Abz-F1 treated-leaves were also lower than those in the untreated control-leaves. Higher 50% effective concentrations (EC(50)) and ascorbic acid concentrations were observed in the Abz-F1 treated-leaves, which show that the oxidative damage under dehydration may be reduced by Abz-F1 application. These results suggest that prompt stomata closure is required for survival under dehydration, and Abz-F1 application may therefore be of practical use. The increase of endogenous ABA, which induced prompt stomata closure in Abz-F1 treated-leaves may depend on inhibition of the expression of MdCYP707As. Furthermore, the results showed the close relationship between MdNCEDs and MdCYP707As on ABA catabolism.
Graduate School of Horticulture, Chiba University, Matsudo 271-8510, Japan. s-kondo@faculty.chiba-u.jp
Satoru
S
Kondo
Sumiko
S
Sugaya
Shun
S
Sugawa
Maki
M
Ninomiya
Monrudee
M
Kittikorn
Katsuya
K
Okawa
Hitoshi
H
Ohara
Kotomi
K
Ueno
Yasushi
Y
Todoroki
Masaharu
M
Mizutani
Nobuhiro
N
Hirai
D000040:Abscisic Acid / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003681:Dehydration / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism*; D027845:Malus / Q000254:growth & development / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism; D014867:Water / Q000378:metabolism
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D010937:Plant Growth Regulators; D010940:Plant Proteins; D014867:Water; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; C107203:abscisic acid 8'-hydroxylase