Abstract
ABSTRACT The acyl-homoserine lactones (AHLs)-mediated LuxI/LuxR quorum sensing (QS) system orchestrates diverse bacterial behaviors in response to changes in population density. The role of the BjaI/BjaR 1 QS system in Bradyrhizobium diazoefficiens USDA 110, which shares homology with LuxI/LuxR, remains elusive during symbiotic interaction with soybean. Here this genetic system in wild-type (WT) bacteria residing inside nodules exhibited significantly reduced activity compared to free-living cells, potentially attributed to soybean-mediated suppression. The deletion mutant strain ΔbjaR 1 showed significantly enhanced nodulation induction and nitrogen fixation ability. Nevertheless, its ultimate symbiotic outcome (plant dry weight) in soybeans was compromised. Furthermore, comparative analysis of the transcriptome, proteome, and promoter activity revealed that the inactivation of BjaR 1 systematically activated and inhibited genomic modules associated with nodulation and nitrogen metabolism. The former appeared to be linked to a significant decrease in the expression of NodD2, a key cell-density-dependent repressor of nodulation genes, while the latter conferred bacterial growth and nitrogen fixation insensitivity to environmental nitrogen. In addition, BjaR 1 exerted a positive influence on the transcription of multiple genes involved in a so-called central intermediate metabolism within the nodule. In conclusion, our findings highlight the crucial role of the BjaI/BjaR 1 QS circuit in positively regulating bacterial nitrogen metabolism and emphasize the significance of the soybean-mediated suppression of this genetic system for promoting efficient symbiotic nitrogen fixation by B. diazoefficiens . IMPORTANCE The present study demonstrates, for the first time, that the BjaI/BjaR1 QS system of Bradyrhizobium diazoefficiens has a significant impact on its nodulation and nitrogen fixation capability in soybean by positively regulating NodD2 expression and bacterial nitrogen metabolism. Moreover, it provides novel insights into the importance of suppressing the activity of this QS circuit by the soybean host plant in establishing an efficient mutual relationship between the two symbiotic partners. This research expands our understanding of legumes’ role in modulating symbiotic nitrogen fixation through rhizobial QS-mediated metabolic functioning, thereby deepening our comprehension of symbiotic coevolution theory. In addition, these findings may hold great promise for developing quorum quenching technology in agriculture.
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Claims 10
Claim · model-written summary
BjaI/BjaR1 system activity was lower in nodule bacteria than free-living cells.
- Taxon
- soybean
Glycine maxe0 - Interactor
- Bradyrhizobium diazoefficiens
Bradyrhizobium diazoefficienst0symbiont - Outcome
- reduced activitye0
- Direction
- reducede0
- Comparator
- free-living cellse0
Not reportedGene
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here this genetic system in wild-type (WT) bacteria residing inside nodules exhibited significantly reduced activity compared to free-living cells, potentially attributed to soybean-mediated suppression.”
t0“Bradyrhizobium diazoefficiens”
Claim · model-written summary
The ΔbjaR 1 strain enhanced nodulation induction.
- Taxon
- SoybeanGlycine maxt0
- Material
- ΔbjaR 1e0
- Treatment
- deletion mutant strain ΔbjaR 1e0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Outcome
- nodulation inductione0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The deletion mutant strain ΔbjaR 1 showed significantly enhanced nodulation induction and nitrogen fixation ability.”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
The ΔbjaR 1 strain enhanced nitrogen fixation ability.
- Taxon
- SoybeanGlycine maxt0
- Material
- ΔbjaR 1e0
- Treatment
- deletion mutant strain ΔbjaR 1e0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Outcome
- nitrogen fixation abilitye0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The deletion mutant strain ΔbjaR 1 showed significantly enhanced nodulation induction and nitrogen fixation ability.”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
The ΔbjaR 1 strain compromised soybean plant dry weight.
- Taxon
- soybeansGlycine maxe0
- Treatment
- BjaI/BjaR 1t0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Outcome
- plant dry weighte0
- Direction
- compromisede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nevertheless, its ultimate symbiotic outcome (plant dry weight) in soybeans was compromised.”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
BjaR 1 inactivation activated genomic modules associated with nodulation.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- inactivation of BjaR 1e0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Gene
- BjaR 1e0
- Outcome
- genomic modules associated with nodulatione0
- Direction
- activatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inactivation of BjaR 1 systematically activated and inhibited genomic modules associated with nodulation and nitrogen metabolism.”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
BjaR 1 inactivation inhibited genomic modules associated with nitrogen metabolism.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- inactivation of BjaR 1e0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Gene
- BjaR 1e0
- Outcome
- genomic modules associated with nodulation and nitrogen metabolisme0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the inactivation of BjaR 1 systematically activated and inhibited genomic modules associated with nodulation and nitrogen metabolism.”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
Nodulation module activation appeared linked to reduced NodD2 expression.
- Taxon
- SoybeanGlycine maxt0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Gene
- NodD2e0
- Outcome
- expression of NodD2e0
- Direction
- decreasee0
- Qualifier
- appeared to be linkede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The former appeared to be linked to a significant decrease in the expression of NodD2, a key cell-density-dependent repressor of nodulation genes”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
The nitrogen metabolism change made bacterial growth insensitive to environmental nitrogen.
- Taxon
- SoybeanGlycine maxt0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Outcome
- bacterial growthe0
- Qualifier
- insensitivity to environmental nitrogene0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the latter conferred bacterial growth and nitrogen fixation insensitivity to environmental nitrogen”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
The nitrogen metabolism change made bacterial nitrogen fixation insensitive to environmental nitrogen.
- Taxon
- SoybeanGlycine maxt0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Outcome
- nitrogen fixation insensitivity to environmental nitrogene0
- Qualifier
- environmental nitrogene0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the latter conferred bacterial growth and nitrogen fixation insensitivity to environmental nitrogen”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”
Claim · model-written summary
BjaR 1 positively affected transcription of central intermediate metabolism genes in nodules.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- nodulee0
- Interactor
- Bradyrhizobium diazoefficiensBradyrhizobium diazoefficienst0symbiont
- Gene
- BjaR 1e0
- Outcome
- transcription of multiple genes involved in a so-called central intermediate metabolisme0
- Direction
- positive influencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“BjaR 1 exerted a positive influence on the transcription of multiple genes involved in a so-called central intermediate metabolism within the nodule”
t0“Soybean-mediated suppression of BjaI/BjaR 1 quorum sensing in Bradyrhizobium diazoefficiens”