A new temperature-insensitive allele of the Arabidopsis AXR6/CUL1 locus derived from a missense mutation in the C-terminal RBX1 binding region

We isolated a new recessive allele at the AUXIN RESISTANT6/CULLIN1 (AXR6/CUL1) locus, axr6–101, from an EMS-mutagenized population of Arabidopsis thaliana, the Landsberg erecta ecotype. axr6–101 is auxin resistant and semi-dwarf similar to the other recessive axr6 mutants. The axr6–101 phenotype is caused by the E716K substitution of the CUL1 protein, which is likely to affect its ability to bind to the C-terminal RING domain of RING-box 1 (RBX1). The previously reported allele of AXR6, cul1–7, is caused by a substitution at T510 that binds to the N-terminal β-strand of RBX1. Although cul1–7 shows temperature-sensitive phenotype, the axr6–101 phenotype is largely unaffected by temperature. axr6–101 may provide an important genetic resource for study of the structure−function relationship of the CUL1 protein.