Abstract
To gain an insight about the mechanism of action of p-chlorophenoxyisobutyric acid (PCIB), which is presumably integrated with auxin signaling pathway, we screened PCIB resistant mutants by monitoring root growth in Arabidopsis. A recessive mutation, aar1 is resistant to 2,4-D while showing a wild-type response to IAA or NAA. Approximately 50 kb genomic DNA is deleted in this mutant at the AAR1 locus in chromosome 4. Any known auxin-related genes and mutants were not found in this region, indicating that aar1 is novel auxin-related mutation. A dominant mutation aar2 was isolated from T-DNA-mutagenized population and T-DNA insertion was detected nearby transcriptional termination site of the AXR6/AtCUL1 gene. In addition, another T-DNA line in which AtCUL1 ORF is disrupted and tir1-1 mutants were also PCIB resistant, suggesting that SCFTIRcomplex has important role for PCIB to inhibit root growth in Arabidopsis.
