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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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SGT1b over-expression antagonizes coi1rsp-dependent RPM1 accumulation and RPM1-mediated disease resistance in rar1.(A) Western blot analysis of RPM1-myc and SGT1b-HA protein levels in indicated genotypes. RuBisCo levels stained by Ponceau S serve as loading control. The result displayed is one of three independent blots giving similar results. (B–C) Bacterial growth analysis of Pto DC3000(avrRpm1) (B) and Pto DC3000(EV) (C). Bacteria were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. Pair-wise comparisons for all means for bacterial growth on day 3 were performed with One-Way ANOVA test followed by Tukey-Kramer HSD at 95% confidence limits. The bacterial growth assays were performed independently three times (Pto DC3000(avrRpm1)) and twice (Pto DC3000(EV)) with similar results.
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pgen-1003018-g006: SGT1b over-expression antagonizes coi1rsp-dependent RPM1 accumulation and RPM1-mediated disease resistance in rar1.(A) Western blot analysis of RPM1-myc and SGT1b-HA protein levels in indicated genotypes. RuBisCo levels stained by Ponceau S serve as loading control. The result displayed is one of three independent blots giving similar results. (B–C) Bacterial growth analysis of Pto DC3000(avrRpm1) (B) and Pto DC3000(EV) (C). Bacteria were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. Pair-wise comparisons for all means for bacterial growth on day 3 were performed with One-Way ANOVA test followed by Tukey-Kramer HSD at 95% confidence limits. The bacterial growth assays were performed independently three times (Pto DC3000(avrRpm1)) and twice (Pto DC3000(EV)) with similar results.

Mentions: Based on this hypothesis, we expected that a high dose of SGT1b would attenuate the rar1 suppression phenotypes of the coi1rsp mutants. To test this, we introduced a 35S:SGT1b-HA construct into coi1-21rsp rar1 plants containing RPM1-myc. Compared with parental coi1-21rsp rar1 plants, four independent T3 lines that expressed relatively high levels of SGT1b::HA exhibited both reduced RPM1-myc levels (Figure 6A) and RPM1-mediated disease resistance (Figure 6B). However, the RPM1 accumulation and RPM1-mediated disease resistance observed in these T3 plants were still much higher than rar1 plants (Figure 6A, 6B). These results demonstrated that modest over-expression of SGT1b can partially inhibit the rar1 suppression phenotypes of coi1rsp alleles. As a control, we measured the growth of Pto DC3000(EV) in the plants used in the Pto DC3000(avrRpm1) growth assay. No enhanced growth of Pto DC3000(EV) was observed in these T3 lines (Figure 6C), demonstrating that the reduction of RPM1-mediated disease resistance in 35S:SGT1b-HA transgenic plants are not due to a decrease in basal defense.


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)

SGT1b over-expression antagonizes coi1rsp-dependent RPM1 accumulation and RPM1-mediated disease resistance in rar1.(A) Western blot analysis of RPM1-myc and SGT1b-HA protein levels in indicated genotypes. RuBisCo levels stained by Ponceau S serve as loading control. The result displayed is one of three independent blots giving similar results. (B–C) Bacterial growth analysis of Pto DC3000(avrRpm1) (B) and Pto DC3000(EV) (C). Bacteria were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. Pair-wise comparisons for all means for bacterial growth on day 3 were performed with One-Way ANOVA test followed by Tukey-Kramer HSD at 95% confidence limits. The bacterial growth assays were performed independently three times (Pto DC3000(avrRpm1)) and twice (Pto DC3000(EV)) with similar results.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1003018-g006: SGT1b over-expression antagonizes coi1rsp-dependent RPM1 accumulation and RPM1-mediated disease resistance in rar1.(A) Western blot analysis of RPM1-myc and SGT1b-HA protein levels in indicated genotypes. RuBisCo levels stained by Ponceau S serve as loading control. The result displayed is one of three independent blots giving similar results. (B–C) Bacterial growth analysis of Pto DC3000(avrRpm1) (B) and Pto DC3000(EV) (C). Bacteria were hand-infiltrated into leaves of each indicated genotype and counted at day 0 and day 3. Error bars represent 2× SE. Pair-wise comparisons for all means for bacterial growth on day 3 were performed with One-Way ANOVA test followed by Tukey-Kramer HSD at 95% confidence limits. The bacterial growth assays were performed independently three times (Pto DC3000(avrRpm1)) and twice (Pto DC3000(EV)) with similar results.
Mentions: Based on this hypothesis, we expected that a high dose of SGT1b would attenuate the rar1 suppression phenotypes of the coi1rsp mutants. To test this, we introduced a 35S:SGT1b-HA construct into coi1-21rsp rar1 plants containing RPM1-myc. Compared with parental coi1-21rsp rar1 plants, four independent T3 lines that expressed relatively high levels of SGT1b::HA exhibited both reduced RPM1-myc levels (Figure 6A) and RPM1-mediated disease resistance (Figure 6B). However, the RPM1 accumulation and RPM1-mediated disease resistance observed in these T3 plants were still much higher than rar1 plants (Figure 6A, 6B). These results demonstrated that modest over-expression of SGT1b can partially inhibit the rar1 suppression phenotypes of coi1rsp alleles. As a control, we measured the growth of Pto DC3000(EV) in the plants used in the Pto DC3000(avrRpm1) growth assay. No enhanced growth of Pto DC3000(EV) was observed in these T3 lines (Figure 6C), demonstrating that the reduction of RPM1-mediated disease resistance in 35S:SGT1b-HA transgenic plants are not due to a decrease in basal defense.

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