title: Specific missense alleles of the arabidopsis jasmonic acid co-receptor COI1 regulate innate immune receptor accumulation and function.
abstract: Plants utilize proteins containing nucleotide binding site (NB) and leucine-rich repeat (LRR) domains as intracellular innate immune receptors to recognize pathogens and initiate defense responses. Since mis-activation of defense responses can lead to tissue damage and even developmental arrest, proper regulation of NB-LRR protein signaling is critical. RAR1, SGT1, and HSP90 act as regulatory chaperones of pre-activation NB-LRR steady-state proteins. We extended our analysis of mutants derived from a rar1 suppressor screen and present two allelic rar1 suppressor (rsp) mutations of Arabidopsis COI1. Like all other coi1 mutations, coi1(rsp) missense mutations impair Jasmonic Acid (JA) signaling resulting in JA-insensitivity. However, unlike previously identified coi1 alleles, both coi1(rsp) alleles lack a male sterile phenotype. The coi1(rsp) mutants express two sets of disease resistance phenotypes. The first, also observed in coi1-1 null allele, includes enhanced basal defense against the virulent bacterial pathogen Pto DC3000 and enhanced effector-triggered immunity (ETI) mediated by the NB-LRR RPM1 protein in both rar1 and wild-type backgrounds. These enhanced disease resistance phenotypes depend on the JA signaling function of COI1. Additionally, the coi1(rsp) mutants showed a unique inability to properly regulate RPM1 accumulation and HR, exhibited increased RPM1 levels in rar1, and weakened RPM1-mediated HR in RAR1. Importantly, there was no change in the steady-state levels or HR function of RPM1 in coi1-1. These results suggest that the coi1(rsp) proteins regulate NB-LRR protein accumulation independent of JA signaling. Based on the phenotypic similarities and genetic interactions among coi1(rsp), sgt1b, and hsp90.2(rsp) mutants, our data suggest that COI1 affects NB-LRR accumulation via two NB-LRR co-chaperones, SGT1b and HSP90. Together, our data demonstrate a role for COI1 in disease resistance independent of JA signaling and provide a molecular link between the JA and NB-LRR signaling pathways.
authors.affiliation: Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Yijian
authors.initials: Y
authors.lastname: He
authors.forename: Eui-Hwan
authors.initials: EH
authors.lastname: Chung
authors.forename: David A
authors.initials: DA
authors.lastname: Hubert
authors.forename: Pablo
authors.initials: P
authors.lastname: Tornero
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D054883:Oxylipins / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology; D012323:RNA Processing, Post-Transcriptional; D011971:Receptors, Immunologic / Q000276:immunology* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003517:Cyclopentanes; D004268:DNA-Binding Proteins; D018841:HSP90 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D054883:Oxylipins; C499581:PBS2 protein, Arabidopsis; C095014:RPM1 protein, Arabidopsis; D011971:Receptors, Immunologic; C452192:SGT1b protein, Arabidopsis; D014157:Transcription Factors; C011006:jasmonic acid