Abstract
The Arabidopsis NPR1 gene was previously shown to be required for the salicylic acid (SA)- and benzothiadiazole (BTH)-induced expression of pathogenesis-related (PR) genes and systemic acquired resistance. The dominant ssi1 (for suppressor of SA insensitivity) mutation characterized in this study defines a new component of the SA signal transduction pathway that bypasses the requirement of NPR1 for expression of the PR genes and disease resistance. The ssi1 mutation caused PR (PR-1, BGL2 [PR-2], and PR-5) genes to be constitutively expressed and restored resistance to an avirulent strain of Pseudomonas syringae pv tomato in npr1-5 (previously called sai1) mutant plants. In addition, ssi1 plants were small, spontaneously developed hypersensitive response-like lesions, accumulated elevated levels of SA, and constitutively expressed the antimicrobial defensin gene PDF1.2. The phenotypes of the ssi1 mutant are SA dependent. When SA accumulation was prevented in ssi1 npr1-5 plants by expressing the SA-degrading salicylate hydroxylase (nahG) gene, all of the phenotypes associated with the ssi1 mutation were suppressed. However, lesion formation and expression of the PR genes were restored in these plants by the application of BTH. Interestingly, expression of PDF1.2, which previously has been shown to be SA independent but jasmonic acid and ethylene dependent, was also suppressed in ssi1 npr1-5 plants by the nahG gene. Furthermore, exogenous application of BTH restored PDF1.2 expression in these plants. Our results suggest that SSI1 may function as a switch modulating cross-talk between the SA- and jasmonic acid/ethylene-mediated defense signal transduction pathways.
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Claims 10
Claim · model-written summary
The ssi1 mutation caused constitutive PR gene expression.
- Taxon
- Arabidopsis
Arabidopsist0 - Treatment
- ssi1 mutatione0
- Gene
- PR (PR-1, BGL2 [PR-2], and PR-5)e0
- Outcome
- PR (PR-1, BGL2 [PR-2], and PR-5) genes to be constitutively expressede0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“The ssi1 mutation caused PR (PR-1, BGL2 [PR-2], and PR-5) genes to be constitutively expressed”
Claim · model-written summary
ssi1 restored resistance to an avirulent Pseudomonas strain in npr1-5 plants.
- Taxon
- ArabidopsisArabidopsist0
- Material
- npr1-5e0
- Interactor
- Pseudomonas syringae pv tomato
Pseudomonas syringaee0pathogen - Outcome
- resistance to an avirulent strain of Pseudomonas syringae pv tomatoe0
- Direction
- restorede0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“restored resistance to an avirulent strain of Pseudomonas syringae pv tomato in npr1-5 (previously called sai1) mutant plants”
Claim · model-written summary
ssi1 plants were small and spontaneously developed lesions.
- Taxon
- ArabidopsisArabidopsist0
- Material
- ssi1e0
- Outcome
- small, spontaneously developed hypersensitive response-like lesionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“ssi1 plants were small, spontaneously developed hypersensitive response-like lesions”
Claim · model-written summary
ssi1 plants accumulated elevated SA levels.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- levels of SAe0
- Direction
- elevatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“accumulated elevated levels of SA”
Claim · model-written summary
ssi1 plants constitutively expressed PDF1.2.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- PDF1.2e0
- Outcome
- constitutively expressed the antimicrobial defensin gene PDF1.2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“constitutively expressed the antimicrobial defensin gene PDF1.2”
Claim · model-written summary
Preventing SA accumulation with nahG suppressed all ssi1 phenotypes.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- expressing the SA-degrading salicylate hydroxylase (nahG) genee0
- Gene
- nahGe0
- Outcome
- all of the phenotypes associated with the ssi1 mutatione0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“When SA accumulation was prevented in ssi1 npr1-5 plants by expressing the SA-degrading salicylate hydroxylase (nahG) gene, all of the phenotypes associated with the ssi1 mutation were suppressed”
Claim · model-written summary
BTH restored lesion formation and PR gene expression in nahG-expressing plants.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- application of BTHe0
- Gene
- PR genese0
- Outcome
- lesion formation and expression of the PR genese0
- Direction
- restorede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“lesion formation and expression of the PR genes were restored in these plants by the application of BTH”
Claim · model-written summary
The nahG gene suppressed PDF1.2 expression in ssi1 npr1-5 plants.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- nahG genee0
- Gene
- PDF1.2e0
- Outcome
- expression of PDF1.2e0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“expression of PDF1.2, which previously has been shown to be SA independent but jasmonic acid and ethylene dependent, was also suppressed in ssi1 npr1-5 plants by the nahG gene”
Claim · model-written summary
Exogenous BTH restored PDF1.2 expression.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- exogenous application of BTHe0
- Gene
- PDF1.2e0
- Outcome
- PDF1.2 expressione0
- Direction
- restorede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“exogenous application of BTH restored PDF1.2 expression in these plants”
Claim · model-written summary
The authors propose SSI1 modulates cross-talk between SA and jasmonic acid/ethylene defense pathways.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- SSI1e0
- Outcome
- cross-talk between the SA- and jasmonic acid/ethylene-mediated defense signal transduction pathwayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis”
e0“SSI1 may function as a switch modulating cross-talk between the SA- and jasmonic acid/ethylene-mediated defense signal transduction pathways”
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loss of function · molecular: expression · ArabidopsisPositive and negative results
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