title: Auxin sensitivities of all Arabidopsis Aux/IAAs for degradation in the presence of every TIR1/AFB.
abstract: Auxin plays a key role in regulation of almost all processes of plant growth and development. Different physiological processes are regulated by different ranges of auxin concentrations; however, the underlying mechanisms creating these differences are largely unknown. The first step of auxin signaling is auxin-dependent interaction of an auxin receptor with transcriptional co-repressors (Aux/IAA), which leads to Aux/IAA degradation. Arabidopsis has six homologous auxin receptors (TIR1 and five AFBs), 29 Aux/IAA proteins and two types of active auxins, IAA and phenylacetic acid (PAA). Therefore, a large number of possible combinations between these three factors may contribute to the creation of complex auxin responses. Using a yeast heterologous reconstitution system, we investigated auxin-dependent degradation of all Arabidopsis Aux/IAAs in combination with every TIR or AFB receptor component. We found that TIR1 and AFB2 were effective in mediating Aux/IAA degradation. We confirmed that the Aux/IAA domain II, which binds TIR1, is essential for degradation. IAA and other natural auxins, 4-chloroindole-3-acetic acid (4-Cl-IAA) and PAA, induced Aux/IAA degradation; and IAA and 4-Cl-IAA had higher activity than PAA. Effective auxin concentrations for Aux/IAA degradation depended on both Aux/IAAs and TIR1 or AFB2 receptors, which is consistent with the Aux/IAA-TIR1/AFB co-receptor concept.
authors.affiliation: Department of Biological Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimizu-Mitao
authors.affiliation: Department of Biological Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 Japan kakimoto@bio.sci.osaka-u.ac.jp.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kakimoto
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology*; D030821:Plants, Genetically Modified; D059748:Proteolysis / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000187:drug effects; D020798:Two-Hybrid System Techniques
chemical_list: C516178:AFB5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; C491592:IAA1 protein, Arabidopsis; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; C501405:TIR1 protein, Arabidopsis
keywords: AFB; Arabidopsis thaliana; Aux/IAA; Auxin; Sensitivity; TIR1