Stationary-phase sigma factor that reprograms RNA polymerase promoter specificity during carbon starvation and general stress adaptation in Pseudomonas putida KT2440. RpoS is a sigma-70 family alternative sigma factor that drives transcription initiation at stationary- and stress-associated promoters, supports starvation survival and cross-protection, and also contributes to condition-specific lifestyle outputs such as biofilm-associated c-di-GMP signaling.
Definition: A sigma factor activity that redirects bacterial RNA polymerase to promoters used during stationary phase and general stress adaptation.
Justification: GO:0016987 captures sigma factor activity broadly, but does not distinguish RpoS-like alternative sigma factors dedicated to stationary-phase and general stress transcriptional programs.
Parent term: sigma factor activity
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003677 DNA binding | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: This term is not entirely wrong because RpoS contributes promoter recognition within RNA polymerase holoenzyme, but it is too generic and potentially misleading as a standalone molecular function. The specific core activity is sigma factor activity, which already captures promoter-specific DNA recognition more accurately. Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md GO:0003677 DNA binding is too generic for a sigma factor whose core activity is promoter specificity within RNA polymerase holoenzyme rather than a standalone DNA-binding regulator. file:PSEPK/rpoS/rpoS-deep-research-falcon.md as a group 2 sigma factor, it binds core RNAP and recognizes promoters similar to RpoD |
| GO:0003700 DNA-binding transcription factor activity | IEA GO_REF:0000002 | MODIFY | Summary: The overall idea that RpoS is a transcriptional regulatory factor is sound, but this GO term is too generic for a bacterial sigma factor. GO:0016987 sigma factor activity is the precise molecular function for the promoter-specificity subunit of RNA polymerase. Reason: Sigma factor activity is the exact and more informative child term for RpoS. Proposed replacements: sigma factor activity Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md GO:0016987 sigma factor activity is the precise molecular function term for RpoS and is more informative than the generic GO:0003700 DNA-binding transcription factor activity. file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS does **not** catalyze a biochemical reaction and is **not** a transporter. Its primary function is **sequence-specific transcription initiation control** |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | ACCEPT | Summary: This annotation is appropriate. RpoS is a bacterial sigma factor that associates with the cytoplasmic RNA polymerase core enzyme and UniProt places the protein in the cytoplasm. Supporting Evidence: file:PSEPK/rpoS/rpoS-uniprot.txt CC -!- SUBCELLULAR LOCATION: Cytoplasm file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS is a **cytosolic** transcription factor (sigma factor) that exerts its function by interacting with **cytosolic RNA polymerase** and promoter DNA. |
| GO:0006352 DNA-templated transcription initiation | IEA GO_REF:0000120 | ACCEPT | Summary: This is a core process annotation for RpoS. Sigma factors function by redirecting RNA polymerase to specific promoters at transcription initiation, and the KT2440 mutant phenotype is consistent with a broad defect in stationary-phase transcriptional reprogramming. Supporting Evidence: file:PSEPK/rpoS/rpoS-deep-research-codex.md Accept GO:0006352 DNA-templated transcription initiation as the direct process executed by RpoS-containing holoenzyme. file:PSEPK/rpoS/rpoS-uniprot.txt CC -!- FUNCTION: Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS does **not** catalyze a biochemical reaction and is **not** a transporter. Its primary function is **sequence-specific transcription initiation control** |
| GO:0006355 regulation of DNA-templated transcription | IEA GO_REF:0000120 | MODIFY | Summary: RpoS certainly regulates transcription, but this term is broader than necessary. The more specific BP term already present in the GOA set is regulation of DNA-templated transcription initiation, which better reflects how sigma factors act. Reason: Replace the broad regulation term with the initiation-specific child term. Proposed replacements: regulation of DNA-templated transcription initiation Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md GO:0006352 DNA-templated transcription initiation and GO:2000142 regulation of DNA-templated transcription initiation capture the direct process-level role better than GO:0006355 regulation of DNA-templated transcription or GO:0010468 regulation of gene expression. file:PSEPK/rpoS/rpoS-deep-research-falcon.md as a group 2 sigma factor, it binds core RNAP and recognizes promoters similar to RpoD |
| GO:0010468 regulation of gene expression | IEA GO_REF:0000104 | MODIFY | Summary: This annotation is directionally correct but far too general. For RpoS, the relevant direct process is regulation of transcription initiation by alternative sigma factor-dependent promoter selection. Reason: GO:2000142 gives the correct level of specificity for RpoS. Proposed replacements: regulation of DNA-templated transcription initiation Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md GO:0006352 DNA-templated transcription initiation and GO:2000142 regulation of DNA-templated transcription initiation capture the direct process-level role better than GO:0006355 regulation of DNA-templated transcription or GO:0010468 regulation of gene expression. |
| GO:0016987 sigma factor activity | IEA GO_REF:0000120 | ACCEPT | Summary: This is the most precise core molecular function for RpoS. It captures the promoter-specificity role of the alternative sigma subunit within RNA polymerase holoenzyme and is directly supported by UniProt and the experimental literature on stationary-phase regulation. Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md GO:0016987 sigma factor activity is the precise molecular function term for RpoS and is more informative than the generic GO:0003700 DNA-binding transcription factor activity. file:PSEPK/rpoS/rpoS-uniprot.txt CC -!- SIMILARITY: Belongs to the sigma-70 factor family. RpoS subfamily. file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS is an alternative sigma factor** (sigma-70 family; βgroup 2β sigma) that binds the **core RNA polymerase** and redirects transcription to a broad set of promoters that support survival during **stationary phase** and diverse stressesβcommonly termed the **general stress response (GSR)** |
| GO:2000142 regulation of DNA-templated transcription initiation | IEA GO_REF:0000108 | ACCEPT | Summary: This is the best specific biological-process term among the seeded GOA set. RpoS changes promoter recognition by RNA polymerase and thereby regulates transcription specifically at the initiation step. Supporting Evidence: file:PSEPK/rpoS/rpoS-deep-research-codex.md Accept GO:2000142 regulation of DNA-templated transcription initiation as the best specific regulatory BP term already present. file:PSEPK/rpoS/rpoS-deep-research-falcon.md A central concept is **sigma competition**: RpoS competes with the housekeeping sigma **RpoD (Ο70)** and other alternative sigmas for a limiting pool of core RNAP. |
| GO:0042594 response to starvation | IMP file:PSEPK/rpoS/rpoS-notes.md | NEW | Summary: The original KT2440 rpoS mutant phenotype directly supports involvement in starvation response. Loss of rpoS reduced survival during carbon starvation, making this a well-supported downstream biological process for the gene. Reason: This term captures the hallmark stationary-phase and starvation phenotype that is not represented in the seeded GOA set. Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md In KT2440, the rpoS mutant showed reduced survival of carbon starvation and reduced cross-protection against other types of stress in cells starved for carbon, and RpoS controlled expression of more than 50 peptides after short carbon starvation. file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS-dependent regulons typically include genes that increase tolerance to oxidative stress, osmotic stress, temperature and pH extremes, and other stationary-phase threats. |
| GO:0006950 response to stress | IMP file:PSEPK/rpoS/rpoS-notes.md | NEW | Summary: RpoS is the master transcriptional regulator of the bacterial general stress response, and in KT2440 its loss reduces cross-protection against multiple stresses in starved cells. This general stress response role is the defining function of RpoS-subfamily sigma factors and complements the more specific response to starvation annotation. Treated as a core downstream process driven by RpoS-dependent promoter reprogramming. Reason: The general stress response is the canonical RpoS function (master regulator of the stationary phase and general stress response) and is not represented in the seeded GOA set. Supporting Evidence: file:PSEPK/rpoS/rpoS-uniprot.txt This sigma factor is the master transcriptional regulator of the stationary phase and the general stress response. file:PSEPK/rpoS/rpoS-deep-research-falcon.md RpoS-dependent regulons typically include genes that increase tolerance to oxidative stress, osmotic stress, temperature and pH extremes, and other stationary-phase threats. |
| GO:0042710 biofilm formation | IMP file:PSEPK/rpoS/rpoS-notes.md | NEW | Summary: Multiple studies place RpoS upstream of biofilm-associated pathways in P. putida, and one recent paper showed direct binding of RpoS to the major wspA promoter with a requirement for tetracycline-induced biofilm formation. This is a justified new annotation, but it should be viewed as a conditional, non-core output of the broader RpoS regulon. Reason: The seeded GOA set misses a recurrent and directly supported RpoS-dependent lifestyle phenotype. Supporting Evidence: file:PSEPK/rpoS/rpoS-notes.md RpoS directly bound the major wspA promoter and was required for tetracycline to induce wspA activity and promote biofilm formation. file:PSEPK/rpoS/rpoS-notes.md Expression of cfcR is transcriptionally regulated by RpoS, and cfcR provides most free c-di-GMP during stationary phase in static conditions. file:PSEPK/rpoS/rpoS-deep-research-falcon.md lapF transcription is described as dependent on RpoS in KT2440 biofilm literature |
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Download this section (compressed HTML)Q: Which promoters constitute the direct core RpoS regulon in KT2440 during carbon starvation versus antibiotic stress?
Q: How broadly conserved is the direct RpoS control of biofilm genes such as wspA, cfcR, lapA, and lapF across environmental conditions relevant to soil and rhizosphere lifestyles?
Q: Which post-transcriptional regulators beyond PsrA most strongly tune RpoS abundance and activity in KT2440?
Experiment: Perform paired RNA-seq and ChIP-seq or ChIP-exo in wild-type and delta-rpoS cells during exponential growth, early carbon starvation, and stationary phase to separate direct promoter targets from indirect downstream effects.
Hypothesis: The direct KT2440 RpoS regulon during starvation is smaller than the full set of downstream stationary-phase phenotypes.
Type: transcriptomics and DNA-binding profiling
Experiment: Measure biofilm formation, c-di-GMP levels, and promoter activity of wspA, cfcR, lapA, and lapF in wild-type, delta-rpoS, and complemented strains under carbon limitation, tetracycline stress, and rhizosphere-mimicking conditions.
Hypothesis: RpoS-dependent biofilm phenotypes arise from a condition-specific promoter subset rather than a universal biofilm program.
Type: targeted genetics and reporter assays
Experiment: Combine translational rpoS reporter fusions with psrA, hfq, and polyphosphate-pathway perturbations to quantify how transcriptional versus post-transcriptional inputs shape RpoS accumulation across the growth curve.
Hypothesis: Upstream regulators such as PsrA and post-transcriptional factors control RpoS at distinct stages of growth-phase transition.
Type: reporter fusion analysis
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