Oligomerization of SCFTIR1 Is Essential for Aux/IAA Degradation and Auxin Signaling in Arabidopsis.
The phytohormone auxin is a key regulator of plant growth and development. Molecular studies in Arabidopsis have shown that auxin perception and signaling is mediated via TIR1/AFB-Aux/IAA co-receptors that assemble as part of the SCFTIR1/AFB E3 ubiquitin-ligase complex and direct the auxin-regulated degradation of Aux/IAA transcriptional repressors. Despite the importance of auxin signaling, little is known about the functional regulation of the TIR1/AFB receptor family. Here we show that TIR1 can oligomerize in planta via a set of spatially clustered amino acid residues. While none of the residues identified reside in the interaction interface of the TIR1-Aux/IAA degron, they nonetheless regulate the binding of TIR1 to Aux/IAA substrate proteins and their subsequent degradation in vivo as an essential aspect of auxin signaling. We propose oligomerization of TIR1 as a novel regulatory mechanism in the regulation of auxin-mediated plant patterning and development.
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
Mohammad H
MH
Dezfulian
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
Espanta
E
Jalili
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
Don Karl A
0000-0001-5938-545X
DK
Roberto
Department of Biology, University of Washington, Seattle, Washington, United States of America.
Britney L
0000-0002-1037-5717
BL
Moss
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
Kerry
K
Khoo
Department of Biology, University of Washington, Seattle, Washington, United States of America.
Jennifer L
JL
Nemhauser
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
William L
WL
Crosby
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D044783:F-Box Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D009097:Multienzyme Complexes; D011956:Receptors, Cell Surface; C501405:TIR1 protein, Arabidopsis; C421912:indole-3-acetic acid synthase