Gibberellin metabolism and signaling.

Gibberellins are plant hormones with a tetracyclic diterpenoid structure that are involved in various important developmental processes. Two gibberellin-deficient mutants were isolated: a semidwarf mutant "sd1," which was found to have a defective GA20ox2 gene and was introduced to the world in a green revolution cultivar, and a severe dwarf allele of "d18," with a defective GA3ox2 gene. Based on the phenotypic similarity of d18, rice dwarf mutants were screened, further classifying them into gibberellin-sensitive and -insensitive by applying exogenous GA3. Finally, GA-deficient rice mutants at six different loci and three gibberellin signaling mutants (gid1, gid2 and slr1) were isolated. The GID1 gene encodes a GA nuclear receptor, and the GID1-DELLA (SLR1) system for gibberellin perception is widely used in vascular plants. The structural characteristics of GID1 and gibberellin metabolic enzymes have also been reviewed.