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8'-Methylene abscisic acid: an effective and persistent analog of abscisic acid

Abrams, S.R., Rose, P.A., Cutler, A.J., Balsevich, J.J., Lei, B., Walker-Simmons, M.K.
Plant physiology 1997 v.114 no.1 pp. 89-97
seed germination, Zea mays, chemical reactions, seedlings, cotyledons, biochemical pathways, carbon, transpiration, Triticum aestivum, growth retardation, gene expression, binding sites, abscisic acid, Lepidium sativum, synthesis, cell suspension culture
We report here the synthesis and biological activity of a new persistent abscisic acid (ABA) analog, 8'-methylene ABA. This ABA analog has one additional carbon atom attached through a double bond to the 8'-carbon of the ABA molecule. (+)-8'-Methylene ABA is more active than the natural hormone (+)-ABA in inhibiting germination of cress seed and excised wheat embryos, in reducing growth of suspension-cultured corn cells, and in reducing transpiration in wheat seedlings. The (+)-8'-methylene analog is slightly weaker than (+)-ABA in increasing expression of ABA-inducible genes in transgenic tobacco, but is equally active in stimulating a transient elevation of the pH of the medium of corn cell cultures. In corn cells, both (+)-ABA and (+)-8'-methylene ABA are oxidized at the 8' position. ABA is oxidized to phaseic acid and (+)-8'-methylene ABA is converted more slowly to two isomeric epoxides. The alteration in the ABA structure causes the analog to be metabolized more slowly than ABA, resulting in longer-lasting and more effective biological activity relative to ABA.