High-affinity siderophore-mediated iron-transport system in the green alga Scenedesmus incrassatulus

Benderliev, Konstantin M.; Ivanova, N. I.

doi:10.1007/bf00192525

Cited by 44 publications

(21 citation statements)

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“…The role of siderophores and the mechanisms of iron acquisition are well known in bacterial and fungal systems (Winkelmann 199 I), but their function in cyanobacterial systems and aquatic iron cycles remains less clear (Wilhelm and Trick 1994). Reports of siderophore production by eucaryotic algae are even rarer (Trick et al 1983;Benderliev and Ivanova 1994), although there are reports of macromolecular algal exudates involved in iron assimilation (Fuse et al 1993).…”

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confidence: 99%

Growth, iron requirements, and siderophore production in iron‐limited Synechococcus PCC 72

Wilhelm

Maxwell

Trick

1996

Limnology & Oceanography

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We have investigated the changes associated with growth over a range of iron availabilities in the cyanobacterium Synechococcus PCC 7002. This cyanobacterium compensates for growth-limiting levels of iron availability by decreasing its maximum growth rate, cellular pigment levels, and apparent iron requirements. This organism also releases extracellular siderophores, which facilitate the acquisition of iron that was previously biologically unavailable from the extracellular environment. Our results suggest a possible ferrisiderophore receptor role for components of the outer membrane and periplasmic space. The resulting change in cellular physiology and activation of a siderophore-mediated iron transport system allows Synechococcus PCC 7002 to re-establish a growth rate comparable to that of cells grown in iron-replete conditions.The utilization of iron from a previously unavailable pool by this cyanobacterium demonstrates that Synechococcus PCC 7002 has a high-affinity iron transport system.

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Section: Acknowledgmentsmentioning

confidence: 99%

Growth, iron requirements, and siderophore production in iron‐limited Synechococcus PCC 72

Wilhelm

Maxwell

Trick

1996

Limnology & Oceanography

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“…Diverse iron assimilation pathways operate in various algae, including siderophore-mediated mechanisms in a Scenedesmus species and a transferrin-dependent pathway in Dunaliella salina (6,28,88). The D. salina extracellular, plasma membrane-associated transferrin is proposed to bind ferric ion generated by a surface-exposed plasma ferroxidase (64).…”

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confidence: 99%

FEA1 , FEA2 , and FRE1 , Encoding Two Homologous Secreted Proteins and a Candidate Ferrireductase, Are Expressed Coordinately with FOX1 and FTR1 in Iron-Deficient Chlamydomonas reinhardtii

et al. 2007

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Previously, we had identified FOX1 and FTR1 as iron deficiency-inducible components of a high-affinity copper-dependent iron uptake pathway in Chlamydomonas. In this work, we survey the version 3.0 draft genome to identify a ferrireductase, FRE1, and two ZIP family proteins, IRT1 and IRT2, as candidate ferrous transporters based on their increased expression in iron-deficient versus iron-replete cells. In a parallel proteomic approach, we identified FEA1 and FEA2 as the major proteins secreted by iron-deficient Chlamydomonas reinhardtii. The recovery of FEA1 and FEA2 from the medium of Chlamydomonas strain CC425 cultures is strictly correlated with iron nutrition status, and the accumulation of the corresponding mRNAs parallels that of the Chlamydomonas FOX1 and FTR1 mRNAs, although the magnitude of regulation is more dramatic for the FEA genes. Like the FOX1 and FTR1 genes, the FEA genes do not respond to copper, zinc, or manganese deficiency. The 5 flanking untranscribed sequences from the FEA1, FTR1, and FOX1 genes confer iron deficiency-dependent expression of ARS2, suggesting that the iron assimilation pathway is under transcriptional control by iron nutrition. Genetic analysis suggests that the secreted proteins FEA1 and FEA2 facilitate high-affinity iron uptake, perhaps by concentrating iron in the vicinity of the cell. Homologues of FEA1 and FRE1 were identified previously as high-CO 2 -responsive genes, HCR1 and HCR2, in Chlorococcum littorale, suggesting that components of the iron assimilation pathway are responsive to carbon nutrition. These iron response components are placed in a proposed iron assimilation pathway for Chlamydomonas.Although iron is abundant in soil, its bioavailability in the aerobic world is poor because of the relative insolubility of Fe(III) and the tight binding of iron to organic chelators (reviewed in references 33, 44, and 56). Iron is therefore one of the essential nutrients that limits virtually all forms of life, and its assimilation involves mechanisms for iron capture from otherwise inaccessible forms plus mechanisms for transport. Many organisms, especially microbes, use multiple pathways for iron uptake because of the varied forms and amounts of iron supply in nature. At the same time, because of its propensity for redox chemistry, especially in an aerobic environment, iron can be toxic to cells. Therefore, the metabolism of iron is very tightly regulated (reviewed in references 9, 13, 22, 41, and 75).Fungi. Because of the importance of iron nutrition to life, the mechanisms of iron assimilation and distribution have been studied in many eukaryotic organisms. One well-studied pathway for iron assimilation was discovered initially through studies of iron metabolism in Saccharomyces cerevisiae. In this pathway, iron is first solubilized by reduction of ferric to ferrous iron and is then available for uptake by high-affinity transporters such as the Fet3p/Ftr1p complex (3,14,27,49,52,72,81,92). There are several transcriptionally regulated FRE genes with different substr...

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“…The siderophore-mediated Fe 3ϩ uptake was first described in bacteria and is characteristic to several algae (1,2) and to grasses (strategy II plants). Redox-mediated iron acquisition, initiated by reduction of ferric to ferrous ions by a plasma membrane ferrireductase, is characteristic to strategy I plants, yeast, and algae (3)(4)(5)(6).…”

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A Multicopper Ferroxidase Involved in Iron Binding to Transferrins in Dunaliella salina Plasma Membranes

Paz

Katz

Pick

2007

Journal of Biological Chemistry

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Iron is an essential element for all photosynthetic organisms because it is a cofactor of multiple components in photosynthetic electron transport. Iron deficiency is a common limitation for plant and algae proliferation because of its low availability in aerobic aqueous solutions. On the other hand, an excess of iron is highly toxic because it can elicit the formation of reactive oxygen species causing oxidative damage. Therefore, all photosynthetic organisms had to develop efficient regulatory mechanisms to control the uptake and storage of iron in order to maintain optimal iron metabolism.Two major strategies of high affinity iron uptake have been demonstrated in plants and in algae as follows: siderophoremediated Fe 3ϩ uptake and a redox-mediated mechanism. The siderophore-mediated Fe 3ϩ uptake was first described in bacteria and is characteristic to several algae (1, 2) and to grasses (strategy II plants). Redox-mediated iron acquisition, initiated by reduction of ferric to ferrous ions by a plasma membrane ferrireductase, is characteristic to strategy I plants, yeast, and algae (3-6). The mechanism of redox-mediated iron uptake in plants differs from that in yeast and in the alga Chlamydomonas reinhardtii in that plants transport the reduced ferrous ions directly via a divalent metal transporter, whereas in yeast and in C. reinhardtii ferrous ions are reoxidized to ferric ions. Reoxidation is mediated by a membranal multicopper ferroxidase, Fet3 or Fox1, belonging to the multicopper oxidase (MCO) 2 superfamily (7,8). Ferric ions are next transported through a coupled ferric-specific transporter. The MCO Fox1 and the iron permease Ftr1 are believed to form a complex at the plasma membrane as demonstrated in yeast (9, 10). Both siderophore and redox-mediated iron uptake are up-regulated under iron deprivation, thus compensating for the decreased iron availability by a more efficient high affinity iron uptake.The halotolerant alga Dunaliella salina is well adapted to iron deprivation, as manifested by its proliferation and by maintenance of photosynthetic activity under iron deprivation (11). We found that D. salina has an unusual mechanism of iron uptake, mediated by binding and internalization of Fe 3ϩ to a surface transferrin-like protein, TTf (12, 13). TTf serves as a housekeeping mechanism for iron uptake, but its expression level and activity are enhanced under iron deprivation or at high salinity, which limits iron availability. The origin of transferrins in Dunaliella is not clear, because no other transferrins have been described so far in other plants or in related organisms. More recently we identified another transferrin, DTf, that is induced under iron deprivation in D. salina plasma membrane. The function of DTf has not been elucidated yet (14).

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High-affinity siderophore-mediated iron-transport system in the green alga Scenedesmus incrassatulus

Cited by 44 publications

References 13 publications

Growth, iron requirements, and siderophore production in iron‐limited Synechococcus PCC 72

Growth, iron requirements, and siderophore production in iron‐limited Synechococcus PCC 72

FEA1 , FEA2 , and FRE1 , Encoding Two Homologous Secreted Proteins and a Candidate Ferrireductase, Are Expressed Coordinately with FOX1 and FTR1 in Iron-Deficient Chlamydomonas reinhardtii

A Multicopper Ferroxidase Involved in Iron Binding to Transferrins in Dunaliella salina Plasma Membranes

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