Mode of Action of Abscisic Acid in Barley Aleurone Layers

Publisher Website
Google Scholar
Abstract
The regulation of ABA metabolism in barley aleurone layers and a few other plant tissues was investigated. The rate of conversion of [3H]ABA to [3H]phaseic acid (PA), the 1st stable metabolite of ABA, is enhanced to 2- to 5-fold in barley aleurone layers when the tissue is pretreated with ABA. The conversion of [3H]PA to [3H] dihydrophaseic acid (DPA), the next metabolite after PA, is not enhanced by pretreatment with either ABA or PA. The ABA enhancement of its own metabolism in barley aleurone layers is detectable with a pretreatment of ABA ranging from 10-8 to 10-4 M. This apparent self-induction of ABA conversion to PA is observed after the barley aleurone layers are treated with 10-5 M ABA for as short as 2 h, and is inhibited by the transcription inhibitor, cordycepin (3''-deoxyadenosine), or the translation inhibitor, cycloheximide. The self-induction of ABA conversion to PA also occurs in wheat [Tritcum aestivum] aleurone layers, but not in other plant tissues that were investigated, including corn [Zea mays] root tips, barley embryos, barley and soybean [Glycine max] leaf discs. It is probably a phenomenon unique to the aleurone layers of some cereal grains. In view of the recent observations that ABA is able to induce new proteins in barley aleurone layers, some of these ABA-induced proteins are apparently involved in the conversion from ABA to PA in this tissue.