title: Effect of K-252a and abscisic acid on the efflux of citrate from soybean roots.
abstract: The Al-induced release of organic acid has been suggested as an important mechanism for Al resistance in plants. In this study, the effect of K-252a and abscisic acid (ABA) on the efflux of citrate was investigated in soybean (Glycine max L.) roots. Al initiated citrate efflux from the root apices 30 min after the addition of Al. The Al-triggered efflux of citrate was sensitive to metabolic inhibitors and anion channel inhibitors. Pretreatment or treatment with K-252a, an inhibitor of protein kinase, severely inhibited the Al-induced efflux of citrate accompanying an increase in Al accumulation and intensified Al-induced root growth inhibition. Al-treatment increased the endogenous level of abscisic acid (ABA) in soybean roots in a dose- and time-dependent manner, while K-252a failed to inhibit the Al-induced increase in endogenous ABA. Exogenous application of ABA increased the activity of citrate synthase (EC 4.1.3.7) by 26.2%, and decreased Al accumulation by 32.3%, respectively. ABA-induced increases in citrate efflux and root elongation were suppressed by K-252a, while ABA could not reverse the K-252a effects. Taken together, these results suggest that ABA is probably involved in the early response, after which K-252a-sensitive protein kinases play a key step in regulating the activity of an anion channel, through which citrate is released from the apical cells of soybean roots.
authors.affiliation: Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki 710-0046, Japan.
authors.forename: Hong
authors.initials: H
authors.lastname: Shen
authors.forename: Ayalew
authors.initials: A
authors.lastname: Ligaba
authors.forename: Mineo
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Osawa
authors.forename: Koichi
authors.initials: K
authors.lastname: Shibata
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Yan
authors.forename: Hideaki
authors.initials: H
authors.lastname: Matsumoto
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000535:Aluminum / Q000378:metabolism / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology*; D002951:Citrates / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D026121:Indole Alkaloids; D007700:Kinetics; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism*; D047428:Protein Kinase Inhibitors; D013025:Glycine max / Q000187:drug effects / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002227:Carbazoles; D002951:Citrates; D004791:Enzyme Inhibitors; D026121:Indole Alkaloids; D047428:Protein Kinase Inhibitors; D000040:Abscisic Acid; C049985:staurosporine aglycone; D014700:Verapamil; D000535:Aluminum