A 25-strain Variovorax collection from Populus roots, screened for bacterial effects on Arabidopsis thaliana thermotolerance using a rapid hydroponic assay. Six strains (CF313, YR634, GV004, GV035, YR752, OV084) significantly improve plant heat tolerance at 45C. CF313 was selected for detailed follow-up study. The thermal benefit requires direct contact with living bacteria; heat-killed bacteria and culture supernatants provide no protection.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Variovorax sp. CF313 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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| Variovorax sp. YR634 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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| Variovorax sp. GV004 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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| Variovorax sp. GV035 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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| Variovorax sp. YR752 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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| Variovorax sp. OV084 — ontology label: Variovorax | NCBITaxon:34072 · TaxonMech · TraitMech | N/A | |
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Ecological Interactions
The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.
Six-Strain Variovorax Thermotolerance Hit Set
Six strains, CF313, YR634, GV004, GV035, YR752 and OV084, each individually improved post-heat-shock Arabidopsis chlorophyll relative to the no-bacteria heat-shocked control in a 25-strain screen. Seedlings received one strain for 7 days before 45 C for 14 min and 4 days recovery; this was not a six-strain consortium. Experimental units were 5-6 wells per strain and 12 control wells, with about 10 seedlings pooled per well and specified outlier removal. No facilitation of bacterial colonization was measured.
Participating Taxa: Variovorax sp. CF313, Variovorax sp. YR634, Variovorax sp. GV004, Variovorax sp. GV035, Variovorax sp. YR752, Variovorax sp. OV084
Biological Processes:
- response to heat (GO:0009408 · PathwayMech)
Evidence
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PMID:37386471 - SUPPORT (IN_VIVO)"plants inoculated with six strains (CF313, YR634, GV004, GV035, YR752, and OV084) showed significantly higher levels of chlorophyll content "
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PMID:37386471 - SUPPORT (IN_VIVO)"Individual strains of Variovorax were added to MS liquid medium to inoculate 7-day-old seedlings and co-cultured for an additional 7 days before heat shock treatment. "
CF313 Follow-Up Thermotolerance Confirmation
In the CF313 follow-up, heat shock reduced chlorophyll 20.4% without bacteria, 17% with living CF313 and 9.3% after thermopriming. This supports a reproducible plant thermotolerance benefit smaller than thermopriming, not a colonization-facilitation phenotype. The reported 9-12 wells per treatment each pool about 10 seedlings; these seedlings are not independent treatment replicates.
Participating Taxa: Variovorax sp. CF313
Biological Processes:
- response to heat (GO:0009408 · PathwayMech)
Evidence
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PMID:37386471 - SUPPORT (IN_VIVO)"These results suggest that CF313 enhanced thermotolerance in Arabidopsis but to a lesser degree than thermo-priming. "
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PMID:37386471 - SUPPORT (IN_VIVO)"Plants inoculated with CF313 (Bac + HS) exhibited 17% reduction of chlorophyll content"
CF313 Live-Cell Versus Killed-Cell and Supernatant Response
Living CF313 provided the plant thermotolerance benefit, whereas heat-killed cells and filtered culture supernatant gave phenotypes similar to the no-bacteria heat-shocked control. HYPOTHESIZED - The authors infer a requirement for direct contact, but no physical-separation experiment is described; these controls do not distinguish contact from ongoing production, unstable signals or host-induced activity by live cells. ACC-deaminase or ethylene signaling was proposed, not tested as the mediator.
Participating Taxa: Variovorax sp. CF313
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:37386471 - SUPPORT (IN_VIVO)"Plants that were inoculated with heat killed CF313 or the supernatant of CF313 culture exhibited similar phenotype with HS plants "
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PMID:37386471 - PARTIAL (IN_VIVO)"indicating that the thermal benefit conferred by CF313 is from direct contact with living bacteria "
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Does CF313 protection require physical contact, or an activity available only during live plant-bacterium coculture?
Preserve positive individual-strain and CF313 results. Assay establishment, duration calibration and screening sequence are methods, not ecological interactions; their three nodes and the remaining workflow arrow are removed. The 14 min regime followed a 12-20 min heat-duration calibration, with a chlorophyll drop after 14 min. Physical separation and pathway perturbations would distinguish contact from ongoing signaling. No mixed six-member community, bacterial colonization outcome or ACC mediation was demonstrated.
Attaches to: ecological_interactions#Six-Strain Variovorax Thermotolerance Hit Set, ecological_interactions#CF313 Follow-Up Thermotolerance Confirmation, ecological_interactions#CF313 Live-Cell Versus Killed-Cell and Supernatant Response
1 evidence item(s)
Plants that were inoculated with heat killed CF313 or the supernatant of CF313 culture exhibited similar phenotype with HS plants
Supports failed protection by non-living bacteria or culture supernatant.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication
A rapid assay for assessing bacterial effects on Arabidopsis thermotolerance. Lee et al. 2023, Plant Methods. |
OTHER | PMID:37386471 |
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Climate-driven plant-microbiome study
Climate-driven divergence in plant-microbiome interactions generates range-wide variation in bud break phenology. Weston, Carrell et al. 2021, Communications Biology. |
OTHER | PMID:34135464 |
Environmental Factors
| Factor | Value | Unit |
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| Heat shock temperature | 45 | degrees Celsius |
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Growth Media
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