In a P. putida KT2440 fliA (sigma-28) mutant, expression of 25 genes was affected (two upregulated, 23 downregulated), including motility and chemotaxis genes; flgM (PP_4395) is part of the sigma-28/FliA-controlled regulatory module, consistent with FliA-dependent transcriptional activation of flgM.

Quote: "In the fliA mutant background expression of 25 genes was affected: two genes were upregulated and 23 genes were downregulated."

Describes the canonical anti-sigma-28 mechanism operating in P. putida KT2440 - the cytoplasmic anti-sigma factor FlgM inhibits the FliA-RNA polymerase association, repressing transcription of late (class IV) flagellar genes until the hook-basal body is complete, at which point FlgM is secreted.

Quote: "FliA and the cytoplasmic anti‐sigma factor FlgM depresses transcription of class IV flagellar genes by inhibiting the FliA‐RNA polymerase association until completion of the hook‐basal body complex, at which point the anti‐sigma factor is secreted"

Establishes the operon context of flgM in P. putida KT2440 - flgM is co-transcribed with pp4396 (FlgN family) and pp4397/flgZ in a flgM-flgN-pp4397 operon, and explicitly identifies flgM as the sigma-FliA anti-sigma-factor gene; the PflgM promoter is sigma-FliA dependent (verified by single-round in vitro transcription with sigma-FliA-RNA polymerase) with read-through from an upstream sigma-54-dependent flgA promoter.

Quote: "co-transcribed with the σFliA anti-σ-factor gene flgM and pp4396 – a gene encoding an FlgN family protein"

Defines the three-tier flagellar transcriptional cascade in P. putida in which FliA (the flagellar sigma factor, a Class II gene product) activates Class III genes enabling filament synthesis; FlgM gates this terminal FliA-dependent step. Provides the regulatory framework placing FlgM-FliA at the late checkpoint of the cascade.

Quote: "FliA activation of Class III genes enables synthesis of the filament, one stator complex and completion of the chemotaxis apparatus."

Authoritative 2024 review synthesizing the FlgM-FliA export checkpoint and its integration with FleQ and c-di-GMP signalling in Pseudomonas; provides transferable mechanistic context for environmental pseudomonads including P. putida (anti-sigma sequestration of FliA relieved by FlgM export after hook-basal body assembly).

UniProt identifies flgM as Negative regulator of flagellin synthesis and supplies function, pathway, family, location, or GO cross-reference evidence used in this review.

The fetched GOA table contains the automated annotations reviewed for flgM.

FlgM is a **protein anti-sigma factor** that binds the flagellar sigma factor **FliA (σ28)** and inhibits FliA-dependent transcription of late/class III-IV flagellar genes until assembly reaches the proper checkpoint.

whose primary molecular role is to **bind/sequester FliA**, preventing FliA from associating with RNA polymerase and thereby blocking FliA-dependent transcription until a defined assembly checkpoint is satisfied.

FlgM is a **cytoplasmic anti-σ factor** that antagonizes **FliA (σ28)**, thereby acting as a **negative regulator of late flagellar gene expression** (including flagellin/filament genes).

FlgM must access FliA and therefore acts **in the cytoplasm** where σ factors and core RNA polymerase interact.

FlgM represses FliA-dependent transcription **until HBB completion**, and **FlgM export/secretion** via the flagellar type III secretion system (FT3SS) relieves this repression by physically removing FlgM from the cytoplasm, freeing FliA.

In *P. putida* KT2440, **flgM** is not an isolated gene: it is co-transcribed in a **flgM–flgN–pp4397 (flgZ)** tricistronic operon, experimentally supported by RT-PCR.

PP_4395** is explicitly annotated as **“Negative regulator of flagellin synthesis FlgM”** and is downregulated when FliA is absent, matching the canonical FliA–FlgM regulatory pair.

**Biological process:** timing/checkpoint control of late flagellar gene expression (filament and motility program) during flagellum biogenesis; integrates into three-tier flagellar transcriptional cascade.