Gibberellin perception in the Avena fatua aleurone

Gibberellins (GAs) are a class of plant hormones involved in the regulation of plant growth and development. A useful model system for studying GA-action is the aleurone layer of cereal grain. In aleurone, GA induces a considerable increase in the rates of transcription of alpha-amylase genes, and this effect can be inhibited by another plant hormone abscisic acid. We anticipate that perception of GA by aleurone cells involves an interaction between the ligand and specific receptors and that this event leads to the observed stimulation in transcription of alpha-amylase, and probably other, aleurone genes. Hormone binding assays with aleurone have not revealed a candidate receptor, and the only aspect of signal transduction that is becoming understood is the likely interaction between specific trans-acting factors and cis-elements in the GA-regulation of alpha-amylase gene transcription. This paper describes the development of novel ways for identifying GA-receptors in aleurone protoplasts of Avena fatua that are based on the use of affinity and antibody probes in functional in vivo assays for GA-receptors. The implications of our current findings are discussed in relation to models of GA-action in aleurone.