Iron limitation results in induction of ferricyanide reductase and ferric chelate reductase activities in Chlamydomonas reinhardtii

Lynnes, Jaret A.; Derzaph, Tina L. M.; Weger, Harold G.

doi:10.1007/s004250050267

Cited by 49 publications

(66 citation statements)

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“…Physiological experiments implied the involvement of reductases in iron assimilation because this activity is induced in iron-deficient cells (22,42,67,114). The question of whether these reductases are iron specific or whether they function also in copper assimilation is unexplored yet because the identity of the enzymes is unknown.…”

Section: Discussionmentioning

confidence: 99%

“…With its simple growth requirements C. reinhardtii is a valuable experimental model for the study of metalloprotein biosynthesis (72,75) and metal-responsive gene regulation in photosynthetic organisms (71). As in other organisms, iron uptake by Chlamydomonas involves reductases (22,42,67,114) that are induced in iron deficiency and may be the same enzyme as that induced in copper-deficient (ϪCu) cells (42). Iron uptake is also induced, although to a lesser extent than Fe 3ϩ reduction (22).…”

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confidence: 99%

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Copper-Dependent Iron Assimilation Pathway in the Model Photosynthetic EukaryoteChlamydomonas reinhardtii

Fontaine

Quinn²,

Nakamoto³

et al. 2002

Eukaryot Cell

185

209

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The unicellular green alga Chlamydomonas reinhardtii is a valuable model for studying metal metabolism in a photosynthetic background. A search of the Chlamydomonas expressed sequence tag database led to the identification of several components that form a copper-dependent iron assimilation pathway related to the high-affinity iron uptake pathway defined originally for Saccharomyces cerevisiae. They include a multicopper ferroxidase (encoded by Fox1), an iron permease (encoded by Ftr1), a copper chaperone (encoded by Atx1), and a copper-transporting ATPase. A cDNA, Fer1, encoding ferritin for iron storage also was identified. Expression analysis demonstrated that Fox1 and Ftr1 were coordinately induced by iron deficiency, as were Atx1 and Fer1, although to lesser extents. In addition, Fox1 abundance was regulated at the posttranscriptional level by copper availability. Each component exhibited sequence relationship with its yeast, mammalian, or plant counterparts to various degrees; Atx1 of C. reinhardtii is also functionally related with respect to copper chaperone and antioxidant activities. Fox1 is most highly related to the mammalian homologues hephaestin and ceruloplasmin; its occurrence and pattern of expression in Chlamydomonas indicate, for the first time, a role for copper in iron assimilation in a photosynthetic species. Nevertheless, growth of C. reinhardtii under copper-and iron-limiting conditions showed that, unlike the situation in yeast and mammals, where copper deficiency results in a secondary iron deficiency, copper-deficient Chlamydomonas cells do not exhibit symptoms of iron deficiency. We propose the existence of a copper-independent iron assimilation pathway in this organism.While iron is abundant in the environment, it is present in the insoluble ferric [Fe(III)] state, so that its bioavailability is low (16). Yet iron is an essential micronutrient for all organisms because it functions as a cofactor in enzymes that catalyze redox reactions in fundamental metabolic processes. Iron exhibits stable, redox-interchangeable ionic states with the potential to generate less stable electron-deficient intermediates during multielectron redox reactions involving oxygen chemistry (16). Therefore, organisms are challenged with the acquisition of sufficient iron to meet cellular metabolic requirements while avoiding uncontrolled intracellular chemistry. This is accomplished via the operation of iron homeostatic mechanisms. The essential features of iron metabolism include assimilation and distribution, storage and sequestration, and utilization and allocation. The assimilatory pathway can be further subdivided into reduction of insoluble ferric species to more soluble ferrous species and uptake into the cell, followed by intracellular transport and intraorganellar distribution. The storage and sequestration of iron involve loading of cellular proteins as well as compartmentalization into organelles like vacuoles and plastids, which in turn requires proteins for transport into and out of these compartm...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Copper-Dependent Iron Assimilation Pathway in the Model Photosynthetic EukaryoteChlamydomonas reinhardtii

Fontaine

Quinn²,

Nakamoto³

et al. 2002

Eukaryot Cell

185

209

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“…Some microorganisms employ an Fe uptake pathway in which Fe(III) is reduced to Fe(II) via superoxide radicals generated by enzymes in the cell membrane (Fujii et al, 2006;Kustka et al, 2005;. Alternatively, Fe(III) can be reduced by membrane reductases (Allnut and Bonner, 1987;Lynnes et al, 1998;Maldonado and Price, 2000;Weger et al, 2002) and additionally via either dissociative or non-dissociative reduction (Salmon et al, 2006) of Fe complexed to Fe-binding ligands.…”

Section: Ferrous Ironmentioning

confidence: 99%

Enhancement of the reactive iron pool by marine diatoms

et al. 2008

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract Short term (2 days) laboratory experiments were performed to study the change in irradiance induced production of Fe(II) in seawater in the presence of two open oceanic Southern Ocean diatom species, Thalassiosira sp. and Chaetoceros brevis. Three irradiance conditions were applied: 1) UVB + UVA + VIS, 2) UVA + VIS, and 3) VIS, and Fe concentrations of 0 and 5 nM Fe were added to natural Southern Ocean seawater (containing 0.32 nM dissolved Fe and 1.69 equivalents of nM L − 1 Fe dissolved organic ligands, log K′ = 22.03). The photoproduced concentration of Fe(II) showed no relationship with the concentration of total dissolved Fe or the concentration of strongly chelated iron. During incubations with the diatoms an increase in the Fe(II) concentration during the second day suggested a modification of the Fe speciation. In the presence of Thalassiosira sp. photoreduction of Fe(III) was observed, whereas in the presence of C. brevis irradiance independent Fe(III) reduction played an important role in the Fe(II) production. Furthermore, a decrease in the strongly chelated Fe concentration, in concert with a decrease in the conditional stability constant, suggested a modification of the strongly chelated Fe fraction in the experiments with C. brevis. The chelated Fe fraction did not change in cultures with Thalassiosira sp. Overall, the presence of diatoms appeared to enhance the reactive Fe pool improving the biological availability of Fe.

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“…This is consistent with a mechanism in which the eukaryotic algae use an uptake system based on iron-reduction at the cell surface followed by ionic Ž iron transport e.g., Soria-Dengg and Horstmann, . 1995; Lynnes et al, 1998 . The uptake of organic Ž .…”

Section: Introductionmentioning

confidence: 99%

Iron availability and the release of iron-complexing ligands by Emiliania huxleyi

Boyé

Berg

2000

Marine Chemistry

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The ubiquitous algal species, Emiliania huxleyi, was incubated in sea water supplemented only with nitrate and Ž . phosphate N and P without chelating agents to control metal speciation. Growth was slow in a ''low-iron'' culture containing 1.3 nM iron and was found to be iron-limited, growth-accelerating when a 1-nM iron addition was made. The Ž .y1 growth rate in a ''high-iron'' culture 5.4 nM iron was greater, reaching 0.4 div day but this culture too was found to have become iron-limited when a 9-nM iron addition was made on day 17 of the incubation. Both cultures were found to release iron-complexing ligands in excess of the iron concentration, 6 nM in the low-iron culture, and 10 nM in the high-iron culture. More ligands were produced after the iron addition taking the ligand concentration to 11 nM in the low-iron culture. The data show that the ligands are released in response to the iron addition, when at least some of the iron had already been taken up. This type of release is contrary to the concept of a siderophore, which is supposed to be released in periods of lack of iron; however the increase in the ligand concentration is similar to that released by the natural community in response to w the iron addition in the IRON-EX II experiment Rue, E.L., Bruland, K.W., 1997. The role of organic complexation on ambient iron chemistry in the equatorial Pacific Ocean and the response of a mesoscale iron addition experiment. Limnol.x Oceanogr. 42, 901-910 . The enhanced growth in the cultures when more iron was added indicated that the organically Ž complexed iron present in the cultures was not immediately available to the organisms or at least not at sufficiently high . rate , and that the organisms responded to freshly added, inorganic, iron. q

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Iron limitation results in induction of ferricyanide reductase and ferric chelate reductase activities in Chlamydomonas reinhardtii

Cited by 49 publications

References 46 publications

Copper-Dependent Iron Assimilation Pathway in the Model Photosynthetic EukaryoteChlamydomonas reinhardtii

Copper-Dependent Iron Assimilation Pathway in the Model Photosynthetic EukaryoteChlamydomonas reinhardtii

Enhancement of the reactive iron pool by marine diatoms

Iron availability and the release of iron-complexing ligands by Emiliania huxleyi

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