title: Toyocamycin specifically inhibits auxin signaling mediated by SCFTIR1 pathway.
abstract: The auxins, plant hormones, play a crucial role in many aspects of plant development by regulating cell division, elongation and differentiation. Toyocamycin, a nucleoside-type antibiotic, was identified as auxin signaling inhibitor in a screen of microbial extracts for inhibition of the auxin-inducible reporter gene assay. Toyocamycin specifically inhibited auxin-responsive gene expression, but did not affect other hormone-inducible gene expression. Toyocamycin also blocked auxin-enhanced degradation of the Aux/IAA repressor modulated by the SCF(TIR1) ubiquitin-proteasome pathway without inhibiting proteolytic activity of proteasome. Furthermore, toyocamycin inhibited auxin-induced lateral root formation and epinastic growth of cotyledon in the Arabidopsis thaliana plant. This evidence suggested that toyocamycin would act on the ubiquitination process regulated by SCF(TIR1) machineries. To address the structural requirements for the specific activity of toyocamycin on auxin signaling, the structure-activity relationships of nine toyocamycin-related compounds, including sangivamycin and tubercidin, were investigated.
authors.affiliation: Department of Biochemistry, Okayama University of Science, 1-1 Ridai-cho, Okayama City 700-0005, Japan. hayashi@dbc.ous.ac.jp
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Hayashi
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kamio
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oono
authors.forename: Leroy B
authors.initials: LB
authors.lastname: Townsend
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nozaki
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics; D007210:Indoleacetic Acids / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D015394:Molecular Structure; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014127:Toyocamycin / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D011956:Receptors, Cell Surface; C501405:TIR1 protein, Arabidopsis; D046988:Proteasome Endopeptidase Complex; D014127:Toyocamycin