Abstract
Gibberellin (GA) regulates various developmental processes in plants. To study on some actions triggered by GA biochemically, we prepared antisera against GA. At first, we used the antisera for the detection of GA in plants. In developing seeds of morning glory and also of Arabidopsis, GA was immunologically detected in their integuments where starch granules were observed and then disappeared. Taking together with other result for related genes expression, we proposed that GA plays a role for seed maturation of dicotyledonous plants at least through the degradation of starch. Secondly, we established a biochemical method for a detection of water - soluble GA receptor candidates in crude solution, which led to the identification of a rice GA receptor, Gibberellin Insensitive Dwarf1 (GID1). Its GA - binding activity and ligand selectivity were confirmed. The suppressor of GA signaling called DELLA boosted the GA - binding activity of GID1 in vitro, which means the formation of a GID1-DELLA complex tightens the binding of GA to GID1. In Arabidopsis, we found three GA receptors. By using loss - of - function mutants, we elucidated the functional redundancy and partial specificity of their receptors. After some approaches, we proposed that the phenotype(s) appeared in the mutants depends on the abundance of the remaining receptor and on its preference to DELLAs.
