title: An E3 ubiquitin ligase, ERECT LEAF1, functions in brassinosteroid signaling of rice.
abstract: A spontaneous rice mutant, erect leaf1 (elf1-1), produced a dwarf phenotype with erect leaves and short grains. Physiological analyses suggested that elf1-1 is brassinosteroid-insensitive, so we hypothesized that ELF1 encodes a positive regulator of brassinosteroid signaling. ELF1, identified by means of positional cloning, encodes a protein with both a U-box domain and ARMADILLO (ARM) repeats. U-box proteins have been shown to function as E3 ubiquitin ligases; in fact, ELF1 possessed E3 ubiquitin ligase activity in vitro. However, ELF1 itself does not appear to be polyubiquitinated. Mutant phenotypes of 2 more elf1 alleles indicate that the entire ARM repeats is indispensable for ELF1 activity. These results suggest that ELF1 ubiquitinates target proteins through an interaction mediated by ARM repeats. Similarities in the phenotypes of elf1 and d61 mutants (mutants of brassinosteroid receptor gene OsBRI1), and in the regulation of ELF1 and OsBRI1 expression, imply that ELF1 functions as a positive regulator of brassinosteroid signaling in rice.
authors.affiliation: RIKEN Advanced Science Institute; Saitama, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: Faculty of Bioresources and Environmental Sciences; Ishikawa Prefectural University; Ishikawa, Japan.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kitano
authors.affiliation: Bioscience and Biotechnology Center; Nagoya University; Aichi, Japan.
authors.forename: Shozo
authors.initials: S
authors.lastname: Fujioka
mesh_terms: D060406:Brassinosteroids / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D009154:Mutation / Q000235:genetics; D012275:Oryza / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D060406:Brassinosteroids; D010940:Plant Proteins; D044767:Ubiquitin-Protein Ligases
keywords: U-box ubiquitin E3 ligase; brassinosteroid insensitive; brassinosteroid signaling; dwarf; mutant; rice