Genes Essential to Iron Transport in the Cyanobacterium Synechocystis sp. Strain PCC 6803

Abstract

Genes encoding polypeptides of an ATP binding cassette (ABC)-type ferric iron transporter that plays a major role in iron acquisition in Synechocystis sp. strain PCC 6803 were identified. These genes are slr1295, slr0513, slr0327, and recently reported sll1878 (Katoh et al., J. Bacteriol. 182:6523-6524, 2000) and were designated futA1, futA2, futB, and futC, respectively, for their involvement in ferric iron uptake. Inactivation of these genes individually or futA1 and futA2 together greatly reduced the activity of ferric iron uptake in cells grown in complete medium or iron-deprived medium. All the fut genes are expressed in cells grown in complete medium, and expression was enhanced by iron starvation. The futA1 and futA2 genes appear to encode periplasmic proteins that play a redundant role in iron binding. The deduced products of futB and futC genes contain nucleotide-binding motifs and belong to the ABC transporter family of inner-membrane-bound and membrane-associated proteins, respectively. These results and sequence similarities among the four genes suggest that the Fut system is related to the Sfu/Fbp family of iron transporters. Inactivation of slr1392, a homologue of feoB in Escherichia coli, greatly reduced the activity of ferrous iron transport. This system is induced by intracellular low iron concentrations that are achieved in cells exposed to iron-free medium or in the fut-less mutants grown in complete medium.

Genome-wide analysis of diel gene expression in the unicellular N2-fixing cyanobacterium Crocosphaera watsonii WH 8501

“…These genes include two feoAB operons encoding a putative ferrous transporter, isiA gene for the iron stress inducible chlorophyll a-binding protein, isiB encoding flavodoxin, and two fur genes (from four genes total) encoding the ferric uptake regulator (Figure 5a, Supplementary Table S1) (Pakrasi et al, 1985;Katoh et al, 2001;Singh et al, 2003;Chappell and Webb, 2009). The third feoAB operon is located in the nif cluster and had an expression pattern identical to nif genes.…”

New insights into iron acquisition by cyanobacteria: an essential role for ExbB-ExbD complex in inorganic iron uptake

“…As genes in the putative exbB-exbD clusters were highly expressed in iron-starved cells, their products are likely involved in iron uptake. Indeed, the expression of several known iron uptake genes (fut and feo genes) (Katoh et al, 2001) is elevated in exbB-exbD mutants (see Supplementary Figure S3 for mutant constructions), even during growth in standard iron-replete conditions (Supplementary Figure S2D). These genes are further expressed in iron-deficient medium (Supplementary Figure S2D), and each exbB gene is enhanced when other homologs are knocked out (Supplementary Figure S2E).…”

Molecular insights into a dinoflagellate bloom

“…Expression of Fe complex transport system has been found to increase under Fe starvation conditions (Katoh et al, 2001;Yuan et al, 2005Yuan et al, , 2008. Thus, the increased expression of genes involved in this system can also serve as a signal of increased Fe demands in dinoflagellates during the bloom.…”