The productivity of the ocean is largely dependent on iron availability, and marine phytoplankton have evolved sophisticated mechanisms to cope with chronically low iron levels in vast regions of the open ocean. By analyzing the metabarcoding data generated from the Tara Oceans expedition, we determined how the global distribution of the model marine chlorarachniophyte Bigelowiella natans varies across regions with different iron concentrations. We performed a comprehensive proteomics analysis of the molecular mechanisms underpinning the adaptation of B. natans to iron scarcity and report on the temporal response of cells to iron enrichment. Our results highlight the role of phytotransferrin in iron homeostasis and indicate the involvement of CREG1 protein in the response to iron availability. Analysis of the Tara Oceans metagenomes and metatranscriptomes also points to a similar role for CREG1, which is found to be widely distributed among marine plankton but to show a strong bias in gene and transcript abundance toward iron-deficient regions. Our analyses allowed us to define a new subfamily of the CobW domain-containing COG0523 putative metal chaperones which are involved in iron metabolism and are restricted to only a few phytoplankton lineages in addition to B. natans. At the physiological level, we elucidated the mechanisms allowing a fast recovery of PSII photochemistry after resupply of iron. Collectively, our study demonstrates that B. natans is well adapted to dynamically respond to a changing iron environment and suggests that CREG1 and COG0523 are important components of iron homeostasis in B. natans and other phytoplankton.

中文翻译：

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绿藻植物 Bigelowiella natans 对铁利用率的复杂反应

海洋的生产力在很大程度上取决于铁的可用性，海洋浮游植物已经进化出复杂的机制来应对公海广大地区铁含量长期较低的情况。通过分析塔拉海洋探险生成的元条形码数据，我们确定了模型海洋绿蛛植物Bigelowiella natans的全球分布如何在铁浓度不同的地区发生变化。我们对B. natans适应铁缺乏的分子机制进行了全面的蛋白质组学分析，并报告了细胞对铁富集的时间反应。我们的结果强调了植物转铁蛋白在铁稳态中的作用，并表明 CREG1 蛋白参与对铁可用性的反应。对塔拉海洋宏基因组和宏转录组的分析也指出了 CREG1 的类似作用，它被发现广泛分布在海洋浮游生物中，但在基因和转录丰度方面显示出对缺铁地区的强烈偏向。我们的分析使我们能够定义包含 CobW 结构域的 COG0523 推定金属伴侣的新亚科，该亚科参与铁代谢，并且仅限于除B. natans之外的少数浮游植物谱系。在生理水平上，我们阐明了补铁后 PSII 光化学快速恢复的机制。总的来说，我们的研究表明B. natans能够很好地适应动态响应不断变化的铁环境，并表明 CREG1 和 COG0523 是B. natans和其他浮游植物铁稳态的重要组成部分。