Isolation and characterization of cul1-7, a recessive allele of CULLIN1 that disrupts SCF function at the C terminus of CUL1 in Arabidopsis thaliana.
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.
Gilkerson
Jonathan
J
Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
Hu
Jianhong
J
Brown
Jessica
J
Jones
Alexander
A
Sun
Tai-ping
TP
Callis
Judy
J
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*
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