Abstract
Changes of the contents and biosynthetic rates of polyamines and enzyme activities involved in polyamine synthesis as affected by dicyclohexylamine (DCHA) were examined in Hiproly barley callus. The incorporation of [1, 4-14C]putrescine into spermidine increased rapidly after auxin withdrawal, while the incorporation of [1, 4-14C]putrescine or [diaminobutane 1, 4-14C]spermidine into spermine increased gently. The addition of DCHA suppressed the incorporation of [3, 4-14C]methionine or [1, 4-14C]putrescine into spermidine. In contrast, the incorporation of [3, 4-14C]methionine or [diaminobutane 1, 4-14C]spermidine into spermine increased in the callus by treatment of DCHA. The contents of spermine in the callus increased about 2-fold after treatment with 10 mM DCHA. The activity of spermidine synthase in the callus after auxin withdrawal increased rapidly. Inhibition of spermidine synthase by DCHA stimulated spermine synthesis and the activity of spermine synthase was elevated about 10-fold after treatment with 10mM DCHA. However, DCHA had significant effects on the activity of S-adenosylmethionine decarboxylase and the levels of S-methyladenosylhomocysteamine. S-Methyladenosylhomocysteamine contents increased about 20-fold. The changes in the spermine levels paralleled the changes in the S-methyladenosylhomocysteamine contents. These results suggested that in Hiproly barley callus the biosynthesis of spermine were regulated by the levels of aminopropyl donor and that the availability of S-methyladenosylhomocysteamine may be rate-limiting for the synthesis of spermine.
