title: Isolation and characterization of cul1-7, a recessive allele of CULLIN1 that disrupts SCF function at the C terminus of CUL1 in Arabidopsis thaliana.
abstract: Many aspects of plant biology depend on the ubiquitin proteasome system for degradation of regulatory proteins. Ubiquitin E3 ligases confer substrate specificity in this pathway, and SCF-type ligases comprise a major class of E3s. SCF ligases have four subunits: SKP1, CUL1, RBX1, and an F-box protein for substrate recognition. The Aux/IAAs are a well-characterized family of SCF substrates in plants. Here, we report characterization of a mutant isolated from a genetic screen in Arabidopsis thaliana designed to identify plants defective in degradation of an Aux/IAA fusion protein, Aux/IAA1-luciferase (IAA1-LUC). This mutant exhibited fourfold slower IAA1-LUC degradation compared with the progenitor line, and seedlings displayed altered auxin responses. Experiments identified the mutant as an allele of CUL1, named cul1-7. The cul1-7 mutation affects the C terminus of the protein, results in reduced cul1-7 levels, and interferes with RBX1 interaction. cul1-7 seedlings are defective in degradation of an endogenous SCF substrate, Repressor of ga1-3 (RGA), and have altered responses to gibberellins. cul1-7 seedlings exhibit slower degradation of the light-labile red/far-red photoreceptor phytochrome A and are photomorphogenic in the dark. This mutation represents the first reported allele of CUL1 to directly affect subunit interactions at the CUL1 C terminus.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gilkerson
authors.forename: Jianhong
authors.initials: J
authors.lastname: Hu
authors.forename: Jessica
authors.initials: J
authors.lastname: Brown
authors.forename: Alexander
authors.initials: A
authors.lastname: Jones
authors.forename: Tai-ping
authors.initials: TP
authors.lastname: Sun
authors.forename: Judy
authors.initials: J
authors.lastname: Callis
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000378:metabolism; D001483:Base Sequence; D044842:Cullin Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism; D005808:Genes, Recessive; D005875:Gibberellins / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000378:metabolism; D051942:Phytochrome A / Q000378:metabolism; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D004268:DNA-Binding Proteins; D005875:Gibberellins; C491592:IAA1 protein, Arabidopsis; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D051942:Phytochrome A; D011993:Recombinant Fusion Proteins; C007842:gibberellic acid; D044843:SKP Cullin F-Box Protein Ligases