Gibberellin A3 Causes a Decrease in the Accumulation of mRNA for ACC Oxidase and in the Activity of the Enzyme in Azuki Bean (Vigna angularis) Epicotyls

Differential screening, aimed at the isolation of cDNA clonesof mRNAs whose accumulation is influenced by GA₃, resulted inthe isolation of a cDNA clone of an mRNA whose level was decreasedby GA₃ in segments of epicotyls of Vigna angularis. The putativeprotein encoded by this cDNA resembled the 1-aminocyclopropane-l-carbox-ylateoxidases (ACC oxidases) identified in other plant species (about80% homology at the amino acid level). Thus, the correspondinggene was designated AB-ACO1 (azuki bean ACC oxidase). GA₃ alsodecreased the activity of ACC oxidase in azuki bean epicotyls,but it did not decrease the rate of ethylene evolution. In fact,GA₃ increased the rate of ethylene evolution and the level ofACC. Thus, GA₃ seemed to increase the production of ethyleneby promoting the synthesis of ACC. (Received January 10, 1997; Accepted July 31, 1997)