Transcriptomic and proteomic responses of the oceanic diatom Pseudo-nitzschia granii to iron limitation: Intracellular processes of an iron-limited diatom

Cohen, Natalie R; Gong, Weida; Moran, Dawn M.; McIlvin, Matthew R.; Saito, Mak A.; Marchetti, Adrian

doi:10.1111/1462-2920.14386

Abstract Diatoms are important primary producers in the world's oceans, yet their growth is constrained in large regions by low bioavailable iron (Fe). Low‐Fe stress‐induced limitation of primary production is due to requirements for Fe in components of essential metabolic pathways including photosynthesis and other chloroplast plastid functions. Studies have shown that under low‐Fe stress, diatoms alter plastid‐specific processes, including components of electron transport. These physiological changes suggest changes of protein content and in protein abundances within the diatom plastid. While in silico predictions provide putative information on plastid‐localized proteins, knowledge of diatom plastid proteins remains limited in comparison to well‐studied model photosynthetic organisms. To address this, we employed shotgun proteomics to investigate the proteome of subcellular plastid‐enriched fractions fromThalassiosira pseudonanato gain a better understanding of how the plastid proteome is remodeled in response to Fe limitation. Using mass spectrometry‐based peptide identification and quantification, we analyzedT. pseudonanagrown under Fe‐replete and ‐limiting conditions. Through these analyses, we inferred the relative quantities of each protein, revealing that Fe limitation regulates major metabolic pathways in the plastid, including the Calvin cycle. Additionally, we observed changes in the expression of light‐harvesting proteins. In silico localization predictions of proteins identified in this plastid‐enriched proteome allowed for an in‐depth comparison of theoretical versus observed plastid‐localization, providing evidence for the potential of additional protein import pathways into the diatom plastid.

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