Genetic Characterization of Mutants Resistant to the Antiauxin p-Chlorophenoxyisobutyric Acid Reveals That AAR3, a Gene Encoding a DCN1-Like Protein, Regulates Responses to the Synthetic Auxin 2,4-Dichlorophenoxyacetic Acid in Arabidopsis Roots

摘要

To isolate novel auxin-responsive mutants in Arabidopsis (Arabidopsis thaliana), we screened mutants for root growth resistancento a putative antiauxin, p-chlorophenoxyisobutyric acid (PCIB), which inhibits auxin action by interfering the upstream auxinsignalingnevents. Eleven PCIB-resistant mutants were obtained. Genetic mapping indicates that the mutations are located in atnleast five independent loci, including two known auxin-related loci, TRANSPORT INHIBITOR RESPONSE1 and ArabidopsisnCULLIN1. antiauxin-resistant mutants (aars) aar3-1, aar4, and aar5 were also resistant to 2,4-dichlorophenoxyacetic acid as shownnby a root growth assay. Positional cloning of aar3-1 revealed that the AAR3 gene encodes a protein with a domain of unknownnfunction (DUF298), which has not previously been implicated in auxin signaling. The protein has a putative nuclear localizationnsignal and shares homology with the DEFECTIVE IN CULLIN NEDDYLATION-1 protein through the DUF298 domain.nThe results also indicate that PCIB can facilitate the identification of factors involved in auxin or auxin-related signaling.