Stringent promoter recognition and autoregulation by the group 3 σ-factor SigF in the cyanobacterium Synechocystis sp. strain PCC 6803

Author:

Asayama Munehiko1,Imamura Sousuke1

Affiliation:

1. Laboratory of Molecular Genetics, School of Agriculture, Ibaraki University, 3-21-1 Ami, Inashiki, Ibaraki 300-0393, Japan

Abstract

Abstract The cyanobacteirum Synechocystis sp. strain PCC 6803 possesses nine species of the sigma (σ)-factor gene for RNA polymerase (RNAP). Here, we identify and characterize the novel-type promoter recognized by a group 3 σ-factor, SigF. SigF autoregulates its own transcription and recognizes the promoter of pilA1 that acts in pilus formation and motility in PCC 6803. The pilA1 promoter (PpilA1-54) was recognized only by SigF and not by other σ-factors in PCC 6803. No PpilA1-54 activity was observed in Escherichia coli cells that possess RpoF (σ28) for fragellin and motility. Studies of in vitro transcription for PpilA1-54 identified the region from −39 to −7 including an AG-rich stretch and a core promoter with TAGGC (-32 region) and GGTAA (-12 region) as important for transcription. We also confirmed the unique PpilA1-54 architecture and further identified two novel promoters, recognized by SigF, for genes encoding periplasmic and phytochrome-like phototaxis proteins. These results and a phylogenetic analysis suggest that the PCC 6803 SigF is distinct from the E. coli RpoF or RpoD (σ70) type and constitutes a novel eubacterial group 3 σ- factor. We discuss a model case of stringent promoter recognition by SigF. Promoter types of PCC 6803 genes are also summarized.

Funder

Ibaraki University

Ministry of Education, Culture, Sports, Science and Technology of Japan

Publisher

Oxford University Press (OUP)

Subject

Genetics

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