UniProt identifies fliA as RNA polymerase sigma factor FliA 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 fliA.

The *Pseudomonas putida* KT2440 gene **fliA** encodes **FliA (σ28; sigma-28 / sigma-F)**, an alternative RNA polymerase sigma factor that directs transcription of **late (flagellar/chemotaxis) genes** in the flagellar regulatory cascade.

**FliA is an alternative sigma factor** that binds core RNA polymerase (RNAP) to alter promoter recognition specificity. In *P. putida* KT2440, this is explicitly described as FliA “conferr[ing] promoter-recognition specificity to core RNA polymerase (RNAP),” consistent with sigma-factor biology.

In KT2440, FliA’s **primary molecular function** is to function as an **RNAP sigma factor** that recognizes **σ28-type promoters** to activate late flagellar/chemotaxis transcription.

**Class III:** **FliA-dependent** transcription enables synthesis of the **filament**, at least one **stator** complex, and completion of the **chemotaxis apparatus**.

In KT2440 the late output of FliA activity is explicitly described: **filament synthesis**, activation of at least one **stator complex**, and completion of the **chemotaxis apparatus**.

FliA is regulated by the **anti-sigma factor FlgM**, which sequesters FliA until flagellar assembly reaches a checkpoint. In *P. putida*, the “final tier” is triggered when FliA is **released from inactivation by FlgM**, after **FlgM secretion via the flagellar type III secretion system (FT3SS)** upon hook completion.

FliA is not a secreted or membrane-embedded protein; it functions by **associating with cytosolic RNAP** and acting at **chromosomal promoters**. KT2440 literature describes FliA as conferring promoter specificity to core RNAP, implying its functional localization is the cytosol/nucleoid region where RNAP-DNA transcription occurs.

Leal-Morales et al. (2022) report systematic promoter motif discovery in the KT2440 flagellar cluster, with **21 putative flagellar promoters** and explicit identification of **FliA-dependent promoter motifs** upstream of **fliK2**, **fliC**, and **cheV**, and additional matches upstream of **fliS** and **flgM**.

A KT2440 targeted mechanistic study demonstrated that **bifA** (encoding a c-di-GMP phosphodiesterase) is **partly controlled by FliA**: