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Specific missense alleles of the arabidopsis jasmonic acid co-receptor COI1 regulate innate immune receptor accumulation and function.

He Y, Chung EH, Hubert DA, Tornero P, Dangl JL - PLoS Genet. (2012)

Bottom Line: The first, also observed in coi1-1 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 results suggest that the coi1(rsp) proteins regulate NB-LRR protein accumulation independent of JA signaling.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

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 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.

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COI1 and HSP90 interact genetically to regulate disease resistance.Bacteria Pto DC3000(avrRpm1) were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. The result displayed is one of two independent analyses giving similar results.
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pgen-1003018-g002: COI1 and HSP90 interact genetically to regulate disease resistance.Bacteria Pto DC3000(avrRpm1) were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. The result displayed is one of two independent analyses giving similar results.

Mentions: To identify new genes that act with RAR1 to regulate NB–LRR accumulation and activation, we performed a suppressor screen for new mutants which can suppress the disease susceptibility observed in rar1-21 (a stop mutation in Q52) [21]. Five rar1 suppressor (rsp) mutants were identified from approximately 200,000 M2 plants from 50 M2 pools that recover resistance responses to both Pto DC3000(avrPphB) and Pto DC3000(avrRpm1) [21]. Based on map-based cloning and subsequent allele sequencing, two of the five mutants were found to have mutations in COI1 (At2g39940). To follow accepted nomenclature conventions, we designated these two mutant alleles, coi1-21rsp and coi1-22rsp, respectively (Figure 1). Based on disease symptoms after inoculation of Pto DC3000(avrRpm1) on backcross F1 and F2 populations, both of the coi1rsp mutants were completely recessive (Table S1). This conclusion was also confirmed by growth assays of Pto DC3000(avrRpm1) in backcross F1 plants (Figure 2). The coi1-21rsp mutation is a G/A transition which leads to a G330E missense change in the COI1 protein. The coi1-22rsp mutation is a G/A transition resulting in a G434E missense change in the protein. Both mutations are within conserved LRR domains (Figure 1). Using the crystal structure of the Arabidopsis COI1 protein, we observed that neither coi1rsp mutation is localized in the interfaces of COI1 that make up the ASK1-binding region and the ligand-binding pocket [31].


Specific missense alleles of the arabidopsis jasmonic acid co-receptor COI1 regulate innate immune receptor accumulation and function.

He Y, Chung EH, Hubert DA, Tornero P, Dangl JL - PLoS Genet. (2012)

COI1 and HSP90 interact genetically to regulate disease resistance.Bacteria Pto DC3000(avrRpm1) were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. The result displayed is one of two independent analyses giving similar results.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475666&req=5

pgen-1003018-g002: COI1 and HSP90 interact genetically to regulate disease resistance.Bacteria Pto DC3000(avrRpm1) were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. The result displayed is one of two independent analyses giving similar results.
Mentions: To identify new genes that act with RAR1 to regulate NB–LRR accumulation and activation, we performed a suppressor screen for new mutants which can suppress the disease susceptibility observed in rar1-21 (a stop mutation in Q52) [21]. Five rar1 suppressor (rsp) mutants were identified from approximately 200,000 M2 plants from 50 M2 pools that recover resistance responses to both Pto DC3000(avrPphB) and Pto DC3000(avrRpm1) [21]. Based on map-based cloning and subsequent allele sequencing, two of the five mutants were found to have mutations in COI1 (At2g39940). To follow accepted nomenclature conventions, we designated these two mutant alleles, coi1-21rsp and coi1-22rsp, respectively (Figure 1). Based on disease symptoms after inoculation of Pto DC3000(avrRpm1) on backcross F1 and F2 populations, both of the coi1rsp mutants were completely recessive (Table S1). This conclusion was also confirmed by growth assays of Pto DC3000(avrRpm1) in backcross F1 plants (Figure 2). The coi1-21rsp mutation is a G/A transition which leads to a G330E missense change in the COI1 protein. The coi1-22rsp mutation is a G/A transition resulting in a G434E missense change in the protein. Both mutations are within conserved LRR domains (Figure 1). Using the crystal structure of the Arabidopsis COI1 protein, we observed that neither coi1rsp mutation is localized in the interfaces of COI1 that make up the ASK1-binding region and the ligand-binding pocket [31].

Bottom Line: The first, also observed in coi1-1 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 results suggest that the coi1(rsp) proteins regulate NB-LRR protein accumulation independent of JA signaling.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

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 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.

Show MeSH
Related in: MedlinePlus