Abstract
Summary Salicylic acid (SA) plays a central role as a signalling molecule involved in plant defense against microbial attack. Genetic manipulation of SA biosynthesis may therefore help to generate plants that are more disease‐resistant. By fusing the two bacterial genes pchA and pchB from Pseudomonas aeruginosa, which encode isochorismate synthase and isochorismate pyruvate‐lyase, respectively, we have engineered a novel hybrid enzyme with salicylate synthase (SAS) activity. The pchB‐A fusion was expressed in Arabidopsis thaliana under the control of the constitutive cauliflower mosaic virus (CaMV) 35S promoter, with targeting of the gene product either to the cytosol (c‐SAS plants) or to the chloroplast (p‐SAS plants). In p‐SAS plants, the amount of free and conjugated SA was increased more than 20‐fold above wild type (WT) level, indicating that SAS is functional in Arabidopsis. P‐SAS plants showed a strongly dwarfed phenotype and produced very few seeds. Dwarfism could be caused by the high SA levels per se or, perhaps more likely, by a depletion of the chorismate or isochorismate pools of the chloroplast. Targeting of SAS to the cytosol caused a slight increase in free SA and a significant threefold increase in conjugated SA, probably reflecting limited chorismate availability in this compartment. Although this modest increase in total SA content did not strongly induce the resistance marker PR‐1, it resulted nevertheless in enhanced disease resistance towards a virulent isolate of Peronospora parasitica . Increased resistance of c‐SAS lines was paralleled with reduced seed production. Taken together, these results illustrate that SAS is a potent tool for the manipulation of SA levels in plants.
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Claims 8
Claim · model-written summary
Chloroplast-targeted SAS increased free and conjugated SA more than 20-fold above WT.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Material
- p‐SAS plantse0
- Treatment
- p‐SASe0
- Outcome
- amount of free and conjugated SAe0
- Direction
- increasede0
- Value
- more than 20‐folde0
- Comparator
- wild type (WT)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In p‐SAS plants, the amount of free and conjugated SA was increased more than 20‐fold above wild type (WT) level”
t0“Arabidopsis thaliana”
Claim · model-written summary
Chloroplast-targeted SAS plants were strongly dwarfed.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- P‐SAS plantse0
- Outcome
- strongly dwarfed phenotypee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P‐SAS plants showed a strongly dwarfed phenotype and produced very few seeds.”
t0“Arabidopsis thaliana”
Claim · model-written summary
Chloroplast-targeted SAS plants produced very few seeds.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- P‐SAS plantse0
- Outcome
- seedse0
- Direction
- very fewe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P‐SAS plants showed a strongly dwarfed phenotype and produced very few seeds.”
t0“Arabidopsis thaliana”
Claim · model-written summary
Cytosol-targeted SAS slightly increased free SA.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Targeting of SAS to the cytosole0
- Outcome
- free SAe0
- Direction
- increasee0
- Qualifier
- slighte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Targeting of SAS to the cytosol caused a slight increase in free SA and a significant threefold increase in conjugated SA”
t0“Arabidopsis thaliana”
Claim · model-written summary
Cytosol-targeted SAS significantly increased conjugated SA threefold.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Targeting of SAS to the cytosole0
- Outcome
- conjugated SAe0
- Direction
- increasee0
- Value
- threefolde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Targeting of SAS to the cytosol caused a slight increase in free SA and a significant threefold increase in conjugated SA”
t0“Arabidopsis thaliana”
Claim · model-written summary
The modest SA increase did not strongly induce PR‐1.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- modest increase in total SA contente0
- Gene
- PR‐1e0
- Outcome
- resistance marker PR‐1e0
- Direction
- did not strongly inducee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this modest increase in total SA content did not strongly induce the resistance marker PR‐1”
t0“Arabidopsis thaliana”
Claim · model-written summary
Cytosol-targeted SAS enhanced resistance to Peronospora parasitica.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- Targeting of SAS to the cytosole1
- Interactor
- Peronospora parasitica
Hyaloperonospora parasiticae0pathogen - Outcome
- disease resistancee0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it resulted nevertheless in enhanced disease resistance towards a virulent isolate of Peronospora parasitica”
e1“Targeting of SAS to the cytosol”
t0“Arabidopsis thaliana”
Claim · model-written summary
Cytosol-targeted SAS lines had reduced seed production alongside increased resistance.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- c‐SAS linese0
- Outcome
- seed productione0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increased resistance of c‐SAS lines was paralleled with reduced seed production.”
t0“Arabidopsis thaliana”
The same questions in other papers
salicylic acid · disease · Arabidopsis thaliana (thale cress)Positive and negative results
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