They effect the attachment of ubiquitin to a DELLA protein, which is then destroyed by proteasomes, thereby relieving the repression of genes, causing stimulated flowering, senescence, conclusion of dormany, and seed germination.
The synthesis of one of these can be prevented by 2-chloroethyl- trimethylammonium chloride, and involves conversion to a hydroxy acid after activation of mevalonate by MVA kinase to form a diterpene precursor, as detailed in papers by Bernard O. Phinney.  In addition to the aforementioned ent-Kaurene, they include those with a lactone ring, as well as one whose methyl ester was separated into free acids named A1, A2, and A3 by Sumuki. They effect the attachment of ubiquitin to a DELLA protein, which is then destroyed by proteasomes, thereby relieving the repression of genes, causing stimulated flowering, senescence, conclusion of dormany, and seed germination. FTP name these plant hormones discovered in the study of foolish seedling disease by Eichi Kurosawa, known to cause stem elongation.
The synthesis of one of these can be prevented by 2-chloroethyl- trimethylammonium chloride, and involves conversion to a hydroxy acid after activation of mevalonate by MVA kinase to form a diterpene precursor, as detailed in papers by Bernard O. Phinney.  
{gibberellin}s