The Involvement of a Multicopper Oxidase in Iron Uptake by the Green Algae <i>Chlamydomonas reinhardtii</i>

Herbik, Alexandra; Bölling, Christian; Buckhout, Thomas J.

doi:10.1104/pp.013060

Cited by 104 publications

(69 citation statements)

References 53 publications

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“…None of the CrZIPs identified in this article appears to be clearly related to this plant iron uptake system. Our findings are in agreement with the results of Herbik et al (2002) and La Fontaine et al (2002), revealing the occurrence in C. reinhardtii of an iron assimilation pathway related to the highaffinity iron uptake pathway of S. cerevisiae (see also below).…”

Section: The Zip Familysupporting

confidence: 82%

A Comparative Inventory of Metal Transporters in the Green Alga Chlamydomonas reinhardtii and the Red Alga Cyanidioschizon merolae

et al. 2005

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As in all organisms, metal cations are crucial for nutrition in plants. Several metals, such as copper, iron, zinc, and manganese, act as important cofactors for many enzymes and are essential for both mitochondrial and chloroplast functions. However, when supplied in excess, these essential cations can become toxic, like heavy metals with no generally established function, such as cadmium, lead, or mercury. To maintain micronutrient metal homeostasis and to cope with the deleterious effects of nonessential heavy metals, plants have developed a complex network of metal uptake, chelation, trafficking, and storage processes. Metal transporters are required to maintain metal homeostasis and thus constitute important components of this network (Clemens, 2001;Hall and Williams, 2003).In recent years, a number of membrane transport protein families have been implicated in metal homeostasis in plants. These include the cation diffusion facilitators (CDF), the Zrt-, Irt-like proteins (ZIP), the cation exchangers (CAX), the copper transporters (COPT), the heavy-metal P-type ATPases (HMA), the natural resistance-associated macrophage proteins (NRAMP), and the ATP-binding cassette (ABC) transporters (Williams et al., 2000;Maser et al., 2001;Cobbett et al., 2003;Hall and Williams, 2003). These transporters are encoded by multigene families. For example, 15 ZIP genes, 12 metal tolerance protein (MTP) genes, and 8 HMA genes are present in the Arabidopsis (Arabidopsis thaliana) genome (Cobbett et al., 2003;Delhaize et al., 2003). However, the transport specificities, patterns of expression, or subcellular localizations of metal transport proteins are still largely unknown. To further understand plant metal homeostasis, it will be necessary to elucidate the contribution of each of these transporters to the uptake, trafficking, and storage of essential metals, as well as to the detoxification of toxic heavy metals.In this article, we present an overview of our current knowledge of the metal transport function in metal homeostasis and tolerance in eukaryotes, with a special emphasis on plants. We also provide a timely inventory of putative metal transporters in two unicellular algal models, the green alga Chlamydomonas reinhardtii and the red alga Cyanidioschizon merolae. These new data should facilitate functional genomics and molecular analysis of metal homeostasis and tolerance in photosynthetic organisms. Moreover, the comparison of metal transporters from species belonging to the red and green algae with those of the land plant Arabidopsis, as well as with their human and yeast homologs, allows some light to be shed on the molecular evolution of metal homeostasis and tolerance systems. TWO UNICELLULAR ALGAL MODEL SYSTEMS

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Section: The Zip Familysupporting

confidence: 82%

A Comparative Inventory of Metal Transporters in the Green Alga Chlamydomonas reinhardtii and the Red Alga Cyanidioschizon merolae

et al. 2005

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“…Elemental analysis was performed by the core facility center of Tsinghua University using an inductively coupled plasma atomic emission spectrometer (Prodigy, Leeman Labs, INC) according to methods published previously [29]. Data were analyzed by SIGMAPLOT (SYSTAT, CA, USA).…”

Section: Elemental Analysismentioning

confidence: 99%

AtbHLH29 of Arabidopsis thaliana is a functional ortholog of tomato FER involved in controlling iron acquisition in strategy I plants

et al. 2005

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AtbHLH29 of Arabidopsis, encoding a bHLH protein, reveals a high similarity to the tomato FER which is proposed as a transcriptional regulator involved in controlling the iron deficiency responses and the iron uptake in tomato. For identification of its biological functions, AtbHLH29 was introduced into the genome of the tomato FER mutant T3238fer mediated by Agrobacterium tumefaciencs. Transgenic plants were regenerated and the stable integration of AtbHLH29 into their genomes was confirmed by Southern hybridization. Molecular analysis demonstrated that expression of the exogenous AtbHLH29 of Arabidopsis in roots of the FER mutant T3238fer enabled to complement the defect functions of FER. The transgenic plants regained the ability to activate the whole iron deficiency responses and showed normal growth as the wild type under iron-limiting stress. Our transformation data demonstrate that AtbHLH29 is a functional ortholog of the tomato FER and can completely replace FER in controlling the effective iron acquisition in tomato. Except of iron, FER protein was directly or indirectly involved in manganese homeostasis due to that loss functions of FER in T3238fer resulted in strong reduction of Mn content in leaves and the defect function on Mn accumulation in leaves was complemented by expression of AtbHLH29 in the transgenic plants. Identification of the similar biological functions of FER and AtbHLH29, which isolated from two systematically wide-diverged "strategy I" plants, suggests that FER might be a universal gene presented in all strategy I plants in controlling effective iron acquisition system in roots.

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“…Numerous studies have been published with respect to its iron homeostasis and consequences of iron deficiency (Allen et al, 2007;La Fontaine et al, 2002;Moseley et al, 2002;Naumann et al, 2005Naumann et al, , 2007, showing that Chlamydomonas reacts in a fine-tuned manner to changing iron availability. The adaptation reactions comprise induction of a copper-dependent high-affinity iron uptake system consisting of the ferroxidase FOX1 and the permease FTR1 (Herbik et al, 2002;La Fontaine et al, 2002), as well as secretion of putative iron-binding proteins such as FEA1 and FEA2 (Allen et al, 2007). Furthermore, a distinct remodeling of photosystem I and its light-harvesting complex under photo-heterotrophic conditions has been described (Naumann et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Ferritin is required for rapid remodeling of the photosynthetic apparatus and minimizes photo‐oxidative stress in response to iron availability in Chlamydomonas reinhardtii

et al. 2008

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SummaryFerritin is a key player in the iron homeostasis due to its ability to store large quantities of iron. Chlamydomonas reinhardtii contains two nuclear genes for ferritin (ferr1 and ferr2) that are induced when Chlamydomonas cells are shifted to iron-deficient conditions. In response to the reduced iron availability, degradation of photosystem I (PSI) and remodeling of its light-harvesting complex occur. This active PSI degradation slows down under photo-autotrophic conditions where photosynthesis is indispensable. We observed a strong induction of ferritin correlated with the degree of PSI degradation during iron deficiency. The PSI level can be restored to normal within 24 h after iron repletion at the expense of the accumulated ferritin, indicating that the ferritin-stored iron allows fast adjustment of the photosynthetic apparatus with respect to iron availability. RNAi strains that are significantly reduced in the amount of ferritin show a striking delay in the degradation of PSI under iron deficiency. Furthermore, these strains are more susceptible to photo-oxidative stress under high-light conditions. We conclude that (i) ferritin is used to buffer the iron released by degradation of the photosynthetic complexes, (ii) the physiological status of the cell determines the strategy used to overcome the impact of iron deficiency, (iii) the availability of ferritin is important for rapid degradation of PSI under iron deficiency, and (iv) ferritin plays a protective role under photo-oxidative stress conditions.

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The Involvement of a Multicopper Oxidase in Iron Uptake by the Green Algae Chlamydomonas reinhardtii

Cited by 104 publications

References 53 publications

A Comparative Inventory of Metal Transporters in the Green Alga Chlamydomonas reinhardtii and the Red Alga Cyanidioschizon merolae

A Comparative Inventory of Metal Transporters in the Green Alga Chlamydomonas reinhardtii and the Red Alga Cyanidioschizon merolae

AtbHLH29 of Arabidopsis thaliana is a functional ortholog of tomato FER involved in controlling iron acquisition in strategy I plants

Ferritin is required for rapid remodeling of the photosynthetic apparatus and minimizes photo‐oxidative stress in response to iron availability in Chlamydomonas reinhardtii

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