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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 100μM 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 …