title: Accelerated shoot overgrowth of rice mutant ao-1 is epistatic to gibberellin-sensitive and -insensitive dwarf mutants.
abstract: A shoot overgrowth mutant of rice ( Oryza sativa L.), accelerated internode overgrowth-1 ( ao-1), is marked by accelerated longitudinal elongation of aerial parts and overgrowth of internodes at the vegetative stage. The physiological properties of ao-1 were similar to those of wild plants treated with a saturating level of exogenous gibberellins (GAs), except for the internode-overgrowth phenotype, which was not mimicked by GA-treated wild plants. The ao-1 mutant was less sensitive to a GA biosynthesis inhibitor, Uniconazole-P, than the wild type. Dwarf alleles of three loci, including two GA-sensitive and one GA-insensitive mutation, were introduced to produce double-mutants with ao-1, but the overgrowth phenotype was not suppressed in double-homozygous mutants. These results suggest that the overgrowth phenotype of ao-1 is caused by abolition of GA signaling rather than by GA overproduction. It is likely that a part of the shoot regulation system of ao-1 is saturated with the GA signal. As a possible model consistent with the results, we propose that AO-1 protein acts as a negative regulator in GA signal transduction.
authors.affiliation: Iwate Biotechnology Research Center, Kitakami, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Aoki
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kitano
authors.forename: Nanako
authors.initials: N
authors.lastname: Kameya
authors.forename: Ikuo
authors.initials: I
authors.lastname: Nakamura