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The hierarchy of transition metal homeostasis: Iron controls manganese accumulation in a unicellular cyanobacterium.

ABSTRACT: Iron and manganese are part of a small group of transition metals required for photosynthetic electron transport. Here, we present evidence for a functional link between iron and manganese homeostasis. In the unicellular cyanobacterium, Synechocystis sp. PCC 6803 Fe and Mn deprivation resulted in distinct modifications of the function of the photosynthetic apparatus. For example, iron limitation modifies the rate of QA re-oxidation in photosystem II, a complex that contains more Mn than Fe. The intracellular elemental quotas of Fe and Mn are also linked. Fe limitation reduces the intracellular Mn quota. Mn limitation did not exert a reciprocal effect on Fe quotas. Microarray analysis comparing Mn and Fe limitation revealed a stark difference in the extent of the transcriptional response to the two limiting conditions, reflective of the physiological data. The effects of Fe limitation on the transcriptional network are widespread while the effects on Mn limitation are highly specific. Our analysis also revealed an overlap in the transcriptional response of specific Fe and Mn transporters. This overlap provides a framework for explaining Fe limitation induced changes in Mn quotas. Fe transporters can serve as a low affinity Mn transport system. Under iron limitation the specificity of the Fe transport system changes, making it a less efficient Mn transport system.

ORGANISM(S): Synechocystis sp. PCC 6803

PROVIDER: GSE48416 | GEO | 2013/06/29

SECONDARY ACCESSION(S): PRJNA209988

REPOSITORIES: GEO

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Project description:Copper and iron are essential micronutrients for most living organisms because they participate as cofactors in biological processes including respiration, photosynthesis and oxidative stress protection. In many eukaryotic organisms, including yeast and mammals, copper and iron homeostases are highly interconnected; however such interdependence is not well established in higher plants. Here we propose that COPT2, a high-affinity copper transport protein, functions under copper and iron deficiencies in Arabidopsis thaliana. COPT2 is a plasma membrane protein that functions in copper acquisition and distribution. Characterization of the COPT2 expression pattern indicates a synergic response to copper and iron limitation in roots. We have characterized a knockout of COPT2, copt2-1, that leads to increased resistance to simultaneous copper and iron deficiencies, measured as reduced leaf chlorosis and improved maintenance of the photosynthetic apparatus. We propose that COPT2 expression could play a dual role under Fe deficiency. First, COPT2 participates in the attenuation of copper deficiency responses driven by iron limitation maybe aimed to minimize further iron consume. On the other hand, global expression analyses of copt2-1 mutants versus wild type Arabidopsis plants indicate that low phosphate responses are increased in copt2-1 plants. In this sense, COPT2 function under Fe deficiency counteracts low phosphate responses. These results open up new biotechnological approaches to fight iron deficiency in crops. Four biological replicates of Arabidopsis seedlings were generated for 2 genotypes, Col-0 and copt2-1 mutant; and 3 growth condictions; first one an iron(Fe) and copper(Cu) sufficient medium (+Fe + Cu), second one an Fe deficient and Cu sufficient medium (-Fe+Cu) and third one an Fe and Cu deficient medium (-Fe-Cu). For each growth one comparasion was made, copt2-1 mutant versus Col-0; in each comparasion four biological replicates were made, two replicas were labeled with Cy5 for the mutant sample and Cy3 for the Col-0 sample, while the other two replicas were reversed-labeled.

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The hierarchy of transition metal homeostasis: Iron controls manganese accumulation in a unicellular cyanobacterium.

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