PLANT PHYSIOLOGY , Vol 114, Issue 1 89-97, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
8[prime]-Methylene Abscisic Acid (An Effective and Persistent Analog of Abscisic Acid)
S. R. Abrams, P. A. Rose, A. J. Cutler, J. J. Balsevich, B. Lei and M. K. Walker-Simmons
Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9 (S.R.A., P.A.R., A.J.C., J.J.B., B.L.)
We report here the synthesis and biological activity of a new persistent
abscisic acid (ABA) analog, 8[prime]-methylene ABA. This ABA analog has one
additional carbon atom attached through a double bond to the
8[prime]-carbon of the ABA molecule. (+)-8[prime]-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[prime]-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[prime]-methylene ABA
are oxidized at the 8[prime] position. ABA is oxidized to phaseic acid and
(+)-8[prime]-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.
