COI1 is a critical component of a receptor for jasmonate and the bacterial virulence factor coronatine.
Jasmonate (JA) is a lipid-derived hormone that regulates diverse aspects of plant immunity and development. An amino acid-conjugated form of JA, jasmonoyl-isoleucine (JA-Ile), stimulates binding of the F-box protein coronatine-insensitive 1 (COI1) to, and subsequent ubiquitin-dependent degradation of, jasmonate ZIM domain (JAZ) proteins that repress transcription of JA-responsive genes. The virulence factor coronatine (COR), which is produced by plant pathogenic strains of Pseudomonas syringae, suppresses host defense responses by activating JA signaling in a COI1-dependent manner. Although previous data indicate that COR acts as a molecular mimic of JA-Ile, the mechanism by which JA-Ile and COR are perceived by plant cells remains unknown. Here, we show that interaction of tomato COI1 with divergent members of the JAZ family is highly specific for JA-Ile and structurally related JA conjugates and that COR is approximately 1,000-fold more active than JA-Ile in promoting this interaction in vitro. JA-Ile competes for binding of COR to COI1-JAZ complexes, demonstrating that COR and JA-Ile are recognized by the same receptor. Binding of COR to the COI1-JAZ complex requires COI1 and is severely impaired by a point mutation in the putative ligand-binding pocket of COI1. Finally, we show that the C-terminal region of JAZ3 containing the highly conserved Jas motif is necessary and sufficient for hormone-induced COI1-JAZ interaction. These findings demonstrate that COI1 is a critical component of the JA receptor and that COR exerts its virulence effects by functioning as a potent agonist of this receptor system.
Katsir
Leron
L
Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
Schilmiller
Anthony L
AL
Staswick
Paul E
PE
He
Sheng Yang
SY
Howe
Gregg A
GA
D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D003517:Cyclopentanes / Q000378:metabolism*; D007192:Indenes / Q000737:chemistry / Q000378:metabolism*; D007532:Isoleucine / Q000378:metabolism; D008024:Ligands; D018551:Solanum lycopersicum / Q000382:microbiology*; D008969:Molecular Sequence Data; D054883:Oxylipins / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D037521:Virulence Factors / Q000737:chemistry / Q000378:metabolism*
D000596:Amino Acids; D003517:Cyclopentanes; D007192:Indenes; D008024:Ligands; D054883:Oxylipins; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D037521:Virulence Factors; D007532:Isoleucine; C058487:coronatine; C011006:jasmonic acid