biostudies-literatureTurnsek JNIEHS NIH HHSBiological and Environmental ResearchGordon and Betty Moore FoundationNational Institutes of HealthCzech Science FoundationNIH HHSNIGMS NIH HHSNational Science FoundationEuropean Regional Development Funde52770https://www.ebi.ac.uk/biostudies/studies/S-EPMC7972479biostudies-literatureUnknown10Iron is a biochemically critical metal cofactor in enzymes involved in photosynthesis, cellular respiration, nitrate assimilation, nitrogen fixation, and reactive oxygen species defense. Marine microeukaryotes have evolved a phytotransferrin-based iron uptake system to cope with iron scarcity, a major factor limiting primary productivity in the global ocean. Diatom phytotransferrin is endocytosed; however, proteins downstream of this environmentally ubiquitous iron receptor are unknown. We applied engineered ascorbate peroxidase APEX2-based subcellular proteomics to catalog proximal proteins of phytotransferrin in the model marine diatom <i>Phaeodactylum tricornutum</i>. Proteins encoded by poorly characterized iron-sensitive genes were identified including three that are expressed from a eLifeProximity proteomics in a marine diatom reveals a putative cell surface-to-chloroplast iron trafficking pathway.PMC7972479GBMF5006F31 1F31ES030613-01NSF-OCE-1756884NSF-MCB-1818390F31 ES030613GBMF3828CZ.02.1.01/0.0/0.0/16_019/0000759GBMF4958DE-SC0018344R24 GM1372001F31ES030613-0121-03224SAllen AEBielinski VABrunson JKViedma MDPMHorak AObornik MTurnsek JDeerinck TJfalseProximity proteomics in a marine diatom reveals a putative cell surface-to-chloroplast iron trafficking pathway.Iron is a biochemically critical metal cofactor in enzymes involved in photosynthesis, cellular respiration, nitrate assimilation, nitrogen fixation, and reactive oxygen species defense. Marine microeukaryotes have evolved a phytotransferrin-based iron uptake system to cope with iron scarcity, a major factor limiting primary productivity in the global ocean. Diatom phytotransferrin is endocytosed; however, proteins downstream of this environmentally ubiquitous iron receptor are unknown. We applied engineered ascorbate peroxidase APEX2-based subcellular proteomics to catalog proximal proteins of phytotransferrin in the model marine diatom <i>Phaeodactylum tricornutum</i>. Proteins encoded by poorly characterized iron-sensitive genes were identified including three that are expressed from a 2021-01-01T00:00:00Z2021 Feb2026-04-13T03:12:40.562Z2025-02-19T02:12:53.86ZS-EPMC79724793359127010.7554/eLife.52770