Abstract
SUMMARY The phytohormone salicylic acid (SA) regulates biotic and abiotic stress responses in plants. Two distinct biosynthetic pathways for SA have been well documented in plants: the isochorismate (IC) pathway in the chloroplast and the phenylalanine ammonia‐lyase (PAL) pathway in the cytosol. However, there has been no solid evidence that the PAL pathway contributes to SA biosynthesis. Here, we report that feeding Arabidopsis thaliana with Ring‐ 13 C‐labeled phenylalanine ( 13 C 6 ‐Phe) resulted in incorporation of the 13 C label not into SA, but into its isomer 4‐hydroxybenzoic acid (4‐HBA) instead. We obtained similar results when feeding 13 C 6 ‐Phe to the SA‐deficient ics1 ics2 mutant and the SA‐hyperaccumulating mutant s3h s5h . Notably, we detected 13 C 6 ‐SA when 13 C 6 ‐benzoic acid (BA) was provided, suggesting that SA can be synthesized from BA. Furthermore, despite the substantial accumulation of SA upon pathogen infection, we did not observe incorporation of 13 C label from Phe into SA. We also did not detect 13 C 6 ‐SA in PAL ‐overexpressing lines in the kfb01 kfb02 kfb39 kfb50 background after being fed 13 C 6 ‐Phe, although endogenous PAL levels were dramatically increased. Based on these combined results, we propose that SA biosynthesis is not from Phe in Arabidopsis . These results have important implications for our understanding of the SA biosynthetic pathway in land plants.
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Claims 6
Claim · model-written summary
Feeding phenylalanine labeled with 13C resulted in label incorporation into 4-hydroxybenzoic acid rather than into SA in Arabidopsis
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Treatment
- phenylalaninee1
- Outcome
- incorporation of the 13 C labele1
- Qualifier
- not into SAe1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“feeding Arabidopsis thaliana with Ring‐ 13 C‐labeled phenylalanine ( 13 C 6 ‐Phe) resulted in incorporation of the 13 C label not into SA, but into its isomer 4‐hydroxybenzoic acid (4‐HBA) instead”
Claim · model-written summary
Similar label results were obtained after feeding 13C6-Phe to the ics1 ics2 SA-deficient mutant
- Taxon
- ArabidopsisArabidopsist0
- Material
- ics1 ics2e2
- Treatment
- Phee2
- Outcome
- similar resultse2
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis”
e2“We obtained similar results when feeding 13 C 6 ‐Phe to the SA‐deficient ics1 ics2 mutant and the SA‐hyperaccumulating mutant s3h s5h”
Claim · model-written summary
Feeding benzoic acid to Arabidopsis produced detectable 13C6-labeled SA
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- benzoic acid (BA)e3
- Outcome
- detected 13 C 6 ‐SAe3
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis”
e3“Notably, we detected 13 C 6 ‐SA when 13 C 6 ‐benzoic acid (BA) was provided, suggesting that SA can be synthesized from BA”
Claim · model-written summary
Despite SA accumulation upon pathogen infection, no 13C label from Phe was incorporated into SA in Arabidopsis
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- pathogen infectione4
- Outcome
- incorporation of 13 C label from Phe into SAe4
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis”
e4“despite the substantial accumulation of SA upon pathogen infection, we did not observe incorporation of 13 C label from Phe into SA”
Claim · model-written summary
No 13C6-SA was detected in PAL-overexpressing lines fed 13C6-Phe, although PAL levels were dramatically increased
- Taxon
- ArabidopsisArabidopsist0
- Material
- kfb01 kfb02 kfb39 kfb50e5
- Treatment
- Phee5
- Gene
- PALe5
- Outcome
- 13 C 6 ‐SAe5
- Qualifier
- although endogenous PAL levels were dramatically increasede5
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“in Arabidopsis”
e5“We also did not detect 13 C 6 ‐SA in PAL ‐overexpressing lines in the kfb01 kfb02 kfb39 kfb50 background after being fed 13 C 6 ‐Phe, although endogenous PAL levels were dramatically increased”
Claim · model-written summary
The authors propose that salicylic acid biosynthesis in Arabidopsis is not from phenylalanine
- Taxon
- ArabidopsisArabidopsise6
- Outcome
- SA biosynthesise6
- Qualifier
- not from Phee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“Based on these combined results, we propose that SA biosynthesis is not from Phe in Arabidopsis”
The same questions in other papers
infection · molecular: metabolites · ArabidopsisPositive and negative results
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See all 10 papers →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.