Genome-wide identification and characterization of Fur-binding sites in the cyanobacteria Synechocystis sp. PCC 6803 and PCC 6714

Abstract

The Ferric uptake regulator (Fur) is crucial to both pathogenic and nonpathogenic bacteria for the maintenance of iron homeostasis as well as the defense against reactive oxygen species. Based on datasets from the genome-wide mapping of transcriptional start sites and transcriptome data, we identified a high confidence regulon controlled by Fur for the model cyanobacterium Synechocystis sp. PCC 6803 and its close relative, strain 6714, based on the conserved strong iron starvation response and Fur binding site occurrence. This regulon comprises 33 protein-coding genes and the sRNA IsaR1 that are under the control of 16 or 14 individual promoters in strains 6803 and 6714, respectively. The associated gene functions are mostly restricted to transporters and enzymes involved in the uptake and storage of iron ions, with few exceptions or unknown functional relevance. Within the isiABC operon, we identified a previously neglected gene encoding a small cysteine-rich protein, which we suggest calling, IsiE. The regulation of iron uptake, storage and utilization ultimately results from the interplay between the Fur regulon, several other transcription factors, the FtsH3 protease and the sRNA IsaR1.

A Four-Step Platform to Optimize Growth Conditions for High-Yield Production of Siderophores in Cyanobacteria

“…The promoter was analysed in silico with the prediction tool BacPP [ 40 ]. The software confirmed the presence in the first 160 bp of the promoter of a binding region for sigma factors σ54 (promoting transcription of genes as consequence of metabolite deprivation) as well as a conserved palindromic binding sequence for Fur proteins [ 41 ] (inhibiting transcription of genes in the presence of iron) ( Figure 1 C).…”

“…In cyanobacteria, the production of siderophore is upregulated under iron limitation. The Iuc operon is transcriptionally regulated by Fe 3+ ions, thanks to cis-acting transcription repressors belonging to the Fur family [ 41 ]. In the presence of iron, Fur proteins bind and repress the Iuc operon.…”

Thioredoxin A regulates protein synthesis to maintain carbon and nitrogen partitioning in cyanobacteria

“…Interestingly, analysis of the STXA2 transcriptome revealed changes related to regulon members of different transcription factors. FurA regulon, recently identified in Synechocystis ( Riediger et al 2021 ), showed a strong downregulation in the STXA2 strain even with inducer ( Fig. 5C ; Supplementary Table S2 ).…”

The Role of FtsH Complexes in the Response to Abiotic Stress in Cyanobacteria

“…Under Fe-rich conditions, Fur predominantly serves as a repressor by binding to specific DNA sequences known as Fur boxes, thus inhibiting the transcription of target genes ( Gonzalez et al. 2014 , Riediger et al. 2021 ).…”