Phytohormones participate in an S6 kinase signal transduction pathway in Arabidopsis.
Addition of fresh medium to stationary cells of Arabidopsis suspension culture induces increased phosphorylation of the S6 ribosomal protein and activation of its cognate kinase, AtS6k. Analysis of the activation response revealed that medium constituents required for S6 kinase activation were the phytohormones 1-naphthylacetic acid (auxin) and kinetin. Pretreatment of cells with anti-auxin or PI3-kinase drugs inhibited this response. Consistent with these findings, LY294002, a PI3-kinase inhibitor, efficiently suppressed phytohormone-induced S6 phosphorylation and translational up-regulation of ribosomal protein S6 and S18A mRNAs without affecting global translation. These data indicate that (1) activation of AtS6k is regulated by phytohormones, at least in part, via a lipid kinase-dependent pathway, that (2) the translational regulation of ribosomal proteins appears to be conserved throughout the plant and animal kingdom, and that (3) these events are hallmarks of a growth-related signal transduction pathway novel in plants.
Turck
Franziska
F
Friedrich Miescher Institute, CH-4002 Basel, Switzerland. turck@mpiz-koeln.mpg.de
Zilbermann
Frederic
F
Kozma
Sara C
SC
Thomas
George
G
Nagy
Ferenc
F
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010937:Plant Growth Regulators / Q000494:pharmacology*; D011132:Polyribosomes / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics / Q000502:physiology
D029681:Arabidopsis Proteins; D004791:Enzyme Inhibitors; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D019893:Ribosomal Protein S6 Kinases