Ostreococcus tauri is a New Model Green Alga for Studying Iron Metabolism in Eukaryotic Phytoplankton

Abstract

YB performed the main experiments and J-CL prepared RNA samples. GL performed all the bioinformatics analyses. EL, RS, IS, P-LB, JP-Y and CB analyzed the data. IS, EL, RS and JP made biochemical experiments. VZ made phylogeny analyses. J-MC and TL analyzed samples by mass spectrometry. GL, J-MC, RS and EL wrote the manuscript. All authors read and approved the final manuscript. Availability of Supporting Data:The data sets supporting the results of this article are included within the article and its additional files.

Copper and iron metabolism in Ostreococcus tauri – the role of phytotransferrin, plastocyanin and a chloroplast copper-transporting ATPase

“…8 To evaluate whether Ot-Fea1 levels correlate with a higher capacity for iron accumulation, we next determined 55 Fe uptake by O. tauri cells grown under iron-replete/-deficient and copperreplete/-deficient conditions. In line with previous reports, 6,13,24 O. tauri cells grown under iron limitation accumulated more 55 Fe than cells grown under iron-replete conditions. In contrast, copper availability did not affect 55 Fe-accumulation by O. tauri cells ( Fig.…”

“…Among the identified proteins, Ot-Fea1 was one of the proteins with the highest score (Table S2, ESI †), establishing this protein as the major iron-binding protein in O. tauri. This result confirms our previous identification of Ot-Fea1 as one of the iron-binding complexes, 13 and is consistent with the growing evidence that Fea1-domain-containing proteins play an important role in iron uptake by marine phytoplankton, including O. tauri. 8,13 Confirming previous results 13 Ot-Fea1 is induced upon iron starvation (Fig.…”

“…S7, ESI †) that, due to its low redox potential, cannot function as an effective electron carrier between the cytochrome b 6 f complex and PSI. 26 Moreover, the expression of this protein in O. tauri is rather low, 13 and we did not identify it in our proteomic data from copper-deprived cells. Thus, plastocyanin seems to be the only protein that can accept electrons from the cytochrome b 6 f complex in O. tauri.…”

“…This concentration of copper exceeds the estimated copper concentration in the surface waters of the open ocean by several times 15 and we have shown previously that it is sufficient to support maximal growth of O. tauri. 13 The growth of O. tauri did not differ significantly between the copper-limiting and copper-sufficient conditions ( Fig. S1A-C, ESI †), but the cellular copper content of cells grown under copper limitation decreased to 9% of that contained in cells grown under copper sufficiency (Fig.…”

“…12 Based on the transcriptomic and bioinformatics data, we have proposed that the components involved in iron acquisition in O. tauri are a ZIP-family protein (Ot-Irt1) and a new Fea1-related protein (Ot-Fea1), a homologue of phytotransferrin in P. tricornutum. 13 Interestingly, Ostreococcus strains isolated from contrasted environments display different levels of adaptation to iron limitation, and the strain with the lowest iron requirements (RCC802) responds to iron deprivation by reduction of the photosynthetic machinery and cell biomass, rather than by cell size reduction. 14 In the present study, we focused on the consequences of copper deprivation in O. tauri.…”