title: AGF1, an AT-hook protein, is necessary for the negative feedback of AtGA3ox1 encoding GA 3-oxidase.
abstract: Negative feedback is a fundamental mechanism of organisms to maintain the internal environment within tolerable limits. Gibberellins (GAs) are essential regulators of many aspects of plant development, including seed germination, stem elongation, and flowering. GA biosynthesis is regulated by the feedback mechanism in plants. GA 3-oxidase (GA3ox) catalyzes the final step of the biosynthetic pathway to produce the physiologically active GAs. Here, we found that only the AtGA3ox1 among the AtGA3ox family of Arabidopsis (Arabidopsis thaliana) is under the regulation of GA-negative feedback. We have identified a cis-acting sequence responsible for the GA-negative feedback of AtGA3ox1 using transgenic plants. Furthermore, we have identified an AT-hook protein, AGF1 (for the AT-hook protein of GA feedback regulation), as a DNA-binding protein for the cis-acting sequence of GA-negative feedback. The mutation in the cis-acting sequence abolished both GA-negative feedback and AGF1 binding. In addition, constitutive expression of AGF1 affected GA-negative feedback in Arabidopsis. Our results suggest that AGF1 plays a role in the homeostasis of GAs through binding to the cis-acting sequence of the GA-negative feedback of AtGA3ox1.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors.forename: Akane
authors.initials: A
authors.lastname: Matsushita
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Furumoto
authors.forename: Sarahmi
authors.initials: S
authors.lastname: Ishida
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D025461:Feedback, Physiological; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000494:pharmacology; D006706:Homeostasis; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment
chemical_list: C521251:AGF1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D005875:Gibberellins; D010937:Plant Growth Regulators; D006899:Mixed Function Oxygenases; C108186:gibberellin 3beta-hydroxylase