Abstract
We have screened Arabidopsis mutants for root growth resistance to a putative antiauxin, p-chlorophenoxyisobutyric acid (PCIB), which inhibits auxin action by interfering the upstream auxin signaling events. In addition to two known auxin-related loci, TIR1 and AtCUL1, we have successfully isolated at least three novel antiauxin-resistant mutants (aars). The aar3 mutant was also resistant to 2,4-D as shown by a root growth assay. The AAR3 gene encodes a protein with a domain of unknown function (DUF298). The protein has a putative nuclear localization signal and its nuclear localization was confirmed by a protoplast transient assay. The protein shares homology with the DEFECTIVE IN CULLIN NEDDYLATION-1 protein through the DUF298 domain. However, no significant difference in the auxin responsive markers, DR5:GUS or HS:AXR3NT-GUS, was observed between the wild type and aar3, suggesting that the AAR3 gene regulates 2,4-D sensitivity through a previously uncharacterized mechanism.
