Abstract
The Arabidopsis ssi4 mutant, which exhibits spontaneous lesion formation, constitutive expression of pathogenesis-related (PR) genes and enhanced resistance to virulent bacterial and oomycete pathogens, contains a gain-of-function mutation in a TIR-NBS-LRR type R gene. Epistatic analyses revealed that both PR gene expression and disease resistance are activated via a salicylic acid (SA)- and EDS1-dependent, but NPR1- and NDR1-independent signaling pathway. In this study, we demonstrate that in moderate relative humidity (RH; 60%), the ssi4 mutant accumulates H(2)O(2) and SA prior to lesion formation and displays constitutive activation of the MAP kinases AtMPK6 and AtMPK3. It also constitutively expresses a variety of defense-associated genes, including those encoding the WRKY transcription factors AtWRKY29 and AtWRKY6, the MAP kinases AtMPK6 and AtMPK3, the powdery mildew R proteins RPW8.1 and RPW8.2, EDS1 and PR proteins. All of these ssi4-induced responses, as well as the chlorotic, stunted morphology and enhanced disease resistance phenotype, are suppressed by high RH (95%) growth conditions. Thus, a humidity sensitive factor (HSF) appears to function at an early point in the ssi4 signaling pathway. All ssi4 phenotypes, except for MAP kinase activation, also were suppressed by the eds1-1 mutation. Thus, ssi4-induced MAP kinase activation occurs downstream of the HSF but either upstream of EDS1 or on a separate branch of the ssi4 signaling pathway. SA is a critical signaling component in ssi4-mediated defense responses. However, exogenously supplied SA failed to restore lesion formation in high RH-grown ssi4 plants, although it induced defense gene expression. Thus, additional signals also are involved.
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Claims 7
Claim · model-written summary
At moderate humidity, ssi4 accumulated hydrogen peroxide and salicylic acid before lesions formed.
- Taxon
- Arabidopsis
Arabidopsise0 - Material
- ssi4e0
- Outcome
- accumulates H(2)O(2) and SAe1
- Setting
- moderate relative humidity (RH; 60%)e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“in moderate relative humidity (RH; 60%), the ssi4 mutant accumulates H(2)O(2) and SA prior to lesion formation”
Claim · model-written summary
At moderate humidity, ssi4 constitutively activated AtMPK6 and AtMPK3.
- Taxon
- ArabidopsisArabidopsise0
- Material
- ssi4e0
- Gene
- AtMPK6 and AtMPK3e1
- Outcome
- constitutive activatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“displays constitutive activation of the MAP kinases AtMPK6 and AtMPK3”
Claim · model-written summary
ssi4 constitutively expressed defense-associated genes.
- Taxon
- ArabidopsisArabidopsise0
- Material
- ssi4e0
- Outcome
- constitutively expresses a variety of defense-associated genese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“It also constitutively expresses a variety of defense-associated genes, including those encoding the WRKY transcription factors AtWRKY29 and AtWRKY6, the MAP kinases AtMPK6 and AtMPK3, the powdery mildew R proteins RPW8.1 and RPW8.2, EDS1 and PR proteins”
Claim · model-written summary
High relative humidity suppressed ssi4 induced responses, chlorosis, stunting and enhanced disease resistance.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- high RH (95%) growth conditionse1
- Outcome
- ssi4-induced responses, as well as the chlorotic, stunted morphology and enhanced disease resistance phenotypee1
- Direction
- suppressede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“All of these ssi4-induced responses, as well as the chlorotic, stunted morphology and enhanced disease resistance phenotype, are suppressed by high RH (95%) growth conditions”
Claim · model-written summary
The eds1-1 mutation suppressed all ssi4 phenotypes except MAP kinase activation.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- eds1-1 mutatione1
- Gene
- eds1-1e1
- Outcome
- All ssi4 phenotypes, except for MAP kinase activatione1
- Direction
- suppressede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“All ssi4 phenotypes, except for MAP kinase activation, also were suppressed by the eds1-1 mutation”
Claim · model-written summary
Exogenous salicylic acid failed to restore lesion formation under high humidity.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- exogenously supplied SAe1
- Outcome
- lesion formatione1
- Direction
- failed to restoree1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“exogenously supplied SA failed to restore lesion formation in high RH-grown ssi4 plants”
Claim · model-written summary
Exogenous salicylic acid induced defense gene expression under high humidity.
- Taxon
- ArabidopsisArabidopsise0
- Treatment
- exogenously supplied SAe1
- Outcome
- defense gene expressione1
- Direction
- inducede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Arabidopsis ssi4 mutant”
e1“exogenously supplied SA failed to restore lesion formation in high RH-grown ssi4 plants, although it induced defense gene expression”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.