The gene rpoF (RNA polymerase, flagellum F) encodes the sigma factor sigma-28 (σ28, or RpoF), a protein in Escherichia coli and other species of bacteria. Depending on the bacterial species, this gene may be referred to as sigD[1] or fliA.[2] The protein encoded by this gene has been found to be necessary for flagellum formation.[3][4][5]