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  • Phosphorylation of D-allose...
    Fukumoto, Takeshi; Kano, Akihito; Ohtani, Kouhei; Inoue, Megumi; Yoshihara, Akihide; Izumori, Ken; Tajima, Shigeyuki; Shigematsu, Yoshio; Tanaka, Keiji; Ohkouchi, Takeo; Ishida, Yutaka; Nishizawa, Yoko; Tada, Yasuomi; Ichimura, Kazuya; Gomi, Kenji; Yoo, Sang-Dong; Sheen, Jen; Akimitsu, Kazuya

    Planta, 05/2013, Volume: 237, Issue: 5
    Journal Article

    We previously reported that a rare sugar D-allose, which is the D-glucose epimer at C3, inhibits the gibberellin-dependent responses such as elongation of the second leaf sheath and induction of α-amylase in embryoless half seeds in rice (Fukumoto et al. 2011). D-Allose suppresses expressions of gibberellin-responsive genes downstream of SLR1 protein in the gibberellin-signaling through hexokinase (HXK)-dependent pathway. In this study, we discovered that D-allose induced expression of ABA-related genes including OsNCED1-3 and OsABA8-ox1-3 in rice. Interestingly, D-allose also up-regulated expression of OsABF1, encoding a conserved bZIP transcription factor in ABA signaling, in rice. The D-allose-induced expression of OsABF1 was diminished by a hexokinase inhibitor, D-mannoheptulose (MNH). Consistently, D-allose also inhibited Arabidopsis growth, but failed to trigger growth retardation in the glucose-insensitive2 (gin2) mutant, which is a loss-of-function mutant of the glucose sensor AtHXK1. D-Allose activated AtABI5 expression in transgenic gin2 over-expressing wild-type AtHXK1 but not in gin2 over-expressing the catalytic mutant AtHXK1 s177A , indicating that the D-allose phosphorylation by HXK to D-allose 6-phosphate (A6P) is the first step for the up-regulation of AtAB15 gene expression as well as D-allose-induced growth inhibition. Moreover, overexpression of OsABF1 showed increased sensitivity to D-allose in rice. These findings indicated that the phosphorylation of D-allose at C6 by hexokinase is essential and OsABF1 is involved in the signal transduction for D-alloseinduced growth inhibition.