title: A 9-cis-epoxycarotenoid dioxygenase inhibitor for use in the elucidation of abscisic acid action mechanisms.
abstract: The plant hormone abscisic acid (ABA) accumulates in response to drought stress and confers stress tolerance to plants. 9-cis-Epoxycarotenoid dioxygenase (NCED), the key regulatory enzyme in the ABA biosynthesis pathway, plays an important role in ABA accumulation. Treatment of plants with abamine, the first NCED inhibitor identified, inhibits ABA accumulation. On the basis of structure-activity relationship studies of abamine, we identified an inhibitor of ABA accumulation more potent than abamine and named it abamineSG. An important structural feature of abamineSG is a three-carbon linker between the methyl ester and the nitrogen atom. Treatment of osmotically stressed plants with 100 microM abamineSG inhibited ABA accumulation by 77% as compared to the control, whereas abamine inhibited the accumulation by 35%. The expression of AB A-responsive genes and ABA catabolic genes was strongly inhibited in abamineSG-treated plants under osmotic stress. AbamineSG is a competitive inhibitor of the enzyme NCED, with a K(i) of 18.5 microM. Although the growth of Arabidopsis seedlings was inhibited by abamine at high concentrations (>50 microM), an effect that was unrelated to the inhibition of ABA biosynthesis, seedling growth was not affected by 100 microM abamineSG. These results suggest that abamineSG is a more potent and specific inhibitor of ABA biosynthesis than abamine.
authors: RIKEN, Saitama, Japan.
authors: Nobutaka
authors: N
authors: Kitahata
authors: Sun-Young
authors: SY
authors: Han
authors: Natsumi
authors: N
authors: Noji
authors: Tamio
authors: T
authors: Saito
authors: Masatomo
authors: M
authors: Kobayashi
authors: Takeshi
authors: T
authors: Nakano
authors: Kazuyuki
authors: K
authors: Kuchitsu
authors: Kazuo
authors: K
authors: Shinozaki
authors: Shigeo
authors: S
authors: Yoshida
authors: Shogo
authors: S
authors: Matsumoto
authors: Masafumi
authors: M
authors: Tsujimoto
authors: Tadao
authors: T
authors: Asami