PLANT PHYSIOLOGY , Vol 106, Issue 4 1279-1284, Copyright © 1994 by American Society of Plant Biologists
|
DEVELOPMENT AND GROWTH REGULATION |
The 7[prime]-Methyl Group of Abscisic Acid Is Critical for Biological Activity in Wheat Embryo Germination
M. K. Walker-Simmons, P. A. Rose, A. C. Shaw and S. R. Abrams
United States Department of Agriculture/Agriculture Research Service, 209 Johnson Hall, Washington State University, Pullman, Washington 99164-6420 (M.K.W.-S.)
Wheat (Triticum aestivum L.) embryo germination is inhibited by natural
(S)-(+)-abscisic acid (ABA). In this report we have determined critical
structural features of the ABA molecule, particularly the methyl and ketone
groups of the ABA ring, required for inhibitory activity. To examine the
ring residues a series of new optically active ABA analogs have been
synthesized in which the 4[prime]-keto, 7[prime]-, 8[prime]-, or 8[prime]-
and 9[prime]-carbons have been replaced with hydrogen atoms. Each of the
analogs was tested over a range of concentrations as a germination
inhibitor. Enantiomers of the analogs altered at the 4[prime]-keto or
8[prime]- and 9[prime]-methyl groups were active, but less so than ABA.
Both enantiomers of 7[prime]-demethylABA were inactive as germination
inhibitors. The results show that the 7[prime]-methyl group is absolutely
required for activity, but that the other residues are less critical for
hormone recognition.
