Abstract
UNLABELLED: Plants use the signaling molecule salicylic acid (SA) to trigger defenses against diverse pathogens, including the bacterial wilt pathogen Ralstonia solanacearum SA can also inhibit microbial growth. Most sequenced strains of the heterogeneous R. solanacearum species complex can degrade SA via gentisic acid to pyruvate and fumarate. R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis. Transcriptional analysis revealed that subinhibitory SA levels induced expression of the SA degradation pathway, toxin efflux pumps, and some general stress responses. Interestingly, SA treatment repressed expression of virulence factors, including the type III secretion system, suggesting that this pathogen may suppress virulence functions when stressed. A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity but retained the wild-type colonization ability and virulence on tomato. This may be because SA is less important than gentisic acid in tomato defense signaling. However, another host, tobacco, responds strongly to SA. To test the hypothesis that SA degradation contributes to virulence on tobacco, we measured the effect of adding this pathway to the tobacco-pathogenic R. solanacearum strain K60, which lacks SA degradation genes. Ectopic addition of the GMI1000 SA degradation locus, including adjacent genes encoding two porins and a LysR-type transcriptional regulator, significantly increased the virulence of strain K60 on tobacco. Together, these results suggest that R. solanacearum degrades plant SA to protect itself from inhibitory levels of this compound and also to enhance its virulence on plant hosts like tobacco that use SA as a defense signal molecule. IMPORTANCE: Plant pathogens such as the bacterial wilt agent Ralstonia solanacearum threaten food and economic security by causing significant losses for small- and large-scale growers of tomato, tobacco, banana, potato, and ornamentals. Like most plants, these crop hosts use salicylic acid (SA) both indirectly as a signal to activate defenses and directly as an antimicrobial chemical. We found that SA inhibits growth of R. solanacearum and induces a general stress response that includes repression of multiple bacterial wilt virulence factors. The ability to degrade SA reduces the pathogen's sensitivity to SA toxicity and increases its virulence on tobacco.
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Claims 6
Claim · model-written summary
Subinhibitory SA levels induced expression of the SA degradation pathway, toxin efflux pumps and some general stress responses in R. solanacearum.
- Taxon
- tomato
Solanum lycopersicume0 - Treatment
- subinhibitory SA levelse1
- Interactor
- R. solanacearum
Ralstonia solanacearume0pathogen - Outcome
- expression of the SA degradation pathway, toxin efflux pumps, and some general stress responsese1
- Direction
- inducede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis”
e1“Transcriptional analysis revealed that subinhibitory SA levels induced expression of the SA degradation pathway, toxin efflux pumps, and some general stress responses”
Claim · model-written summary
SA treatment repressed expression of virulence factors, including the type III secretion system, in R. solanacearum.
- Taxon
- tomatoSolanum lycopersicume0
- Treatment
- SA treatmente2
- Outcome
- expression of virulence factorse2
- Direction
- repressede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis”
e2“Interestingly, SA treatment repressed expression of virulence factors, including the type III secretion system”
Claim · model-written summary
A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity.
- Taxon
- tomatoSolanum lycopersicume3
- Treatment
- SAe3
- Outcome
- susceptible to SA toxicitye3
- Direction
- much more susceptiblee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity but retained the wild-type colonization ability and virulence on tomato”
Claim · model-written summary
The GMI1000 mutant lacking SA degradation activity retained wild-type colonization ability and virulence on tomato.
- Taxon
- tomatoSolanum lycopersicume3
- Outcome
- colonization ability and virulencee3
- Comparator
- wild-typee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity but retained the wild-type colonization ability and virulence on tomato”
Claim · model-written summary
Adding the GMI1000 SA degradation locus significantly increased the virulence of R. solanacearum strain K60 on tobacco.
- Taxon
- tobacco
Nicotiana tabacume4 - Treatment
- Ectopic addition of the GMI1000 SA degradation locuse4
- Interactor
- R. solanacearumRalstonia solanacearume5pathogen
- Outcome
- virulencee4
- Direction
- significantly increasede4
- Comparator
- strain K60e4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Ectopic addition of the GMI1000 SA degradation locus, including adjacent genes encoding two porins and a LysR-type transcriptional regulator, significantly increased the virulence of strain K60 on tobacco”
e5“we measured the effect of adding this pathway to the tobacco-pathogenic R. solanacearum strain K60”
Claim · model-written summary
SA inhibits growth of R. solanacearum on tomato and induces a general stress response that represses bacterial wilt virulence factors.
- Taxon
- tomatoSolanum lycopersicume0
- Treatment
- SAe6
- Interactor
- R. solanacearumRalstonia solanacearume6pathogen
- Outcome
- growth of R. solanacearume6
- Direction
- inhibitse6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis”
e6“We found that SA inhibits growth of R. solanacearum and induces a general stress response that includes repression of multiple bacterial wilt virulence factors”
The same questions in other papers
salicylic acid · Ralstonia solanacearum · Nicotiana tabacum (tobacco)Positive and negative results
1 in the opposite direction
- positive
salicylic acid · Ralstonia solanacearum · Solanum lycopersicum (tomato)Results agree
6 papers in the same direction as this paper
- positive
- positive
- positive
3 papers more in this group
See all 7 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.