{
  "abstract": "{sigma}-factors are dissociable subunits of RNA polymerase (RNAP), forming the basal regulatory machinery for bacterial transcription. The minimal {sigma}-factors contain two domains (called {sigma}2 or {sigma}4), both of which bind RNAP as well as the promoter DNA through their helix-turn-helix motif. Housekeeping {sigma}-factors contain four domains. We identify proteins containing at least one of the four {sigma}-factor domains in bacterial and bacteriophage genomes; we also show that proteins containing either {sigma}2 or {sigma}4, which are not defined as {sigma}-factors, are commonly found in both sets of organisms. Using phylogenetic analysis of these two domains, we suggest that the highly conserved major housekeeping {sigma}-factor, with its complex domain architecture, represents a late-evolving monophyletic clade, whereas single-domain proteins and minimal {sigma}-factor architectures comprising {sigma}2 and {sigma}4 might be ancestral. Thus, {sigma}-factors probably evolved from single-domain DNA-binding transcription factors by domain accretion.",
  "abstract_shown": true,
  "affiliations": [
    "National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, 560065, India"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "name": "P. Tiwary"
    },
    {
      "affs": [
        0
      ],
      "name": "A. S. N. Seshasayee"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2z5bwz910v7wm.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.08.757525",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1.full",
  "id": "2z5bwz910v7wm",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1",
  "language": null,
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "evolutionary biology"
    ],
    [
      "openalex",
      "1311|Bacterial Genetics and Biotechnology"
    ]
  ],
  "openalex": "W7221327492",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/2z5bwz910v7wm.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:26:57Z",
      "native_id": "10.64898/2026.10.08.757525",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:evolutionary biology",
      "subfield": "evolutionary-biology"
    }
  ],
  "title": "Phylogenetic evidence for the emergence of bacterial σ-factors by domain fusion",
  "title_text": "Phylogenetic evidence for the emergence of bacterial σ-factors by domain fusion",
  "type": "preprint",
  "updated_at": "2026-10-30T12:26:57Z",
  "url": "https://research.draconitic.com/paper/2z5bwz910v7wm",
  "venue": "bioRxiv",
  "versions": []
}