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This dataset includes depth profiles in the euphotic zone of nutrient (nitrate, silicate, phosphate) concentrations and profiles of silicic acid uptake rates from EXPORTS cruise RR1813. The EXPORTS field campaign in the subarctic North Pacific sampled an ecosystem characterized as high nutrient low chlorophyll (HNLC) due to low iron (Fe) levels that are primary controllers constraining phytoplankton utilization of other nutrients. It has been a paradigm in low Fe, HNLC systems that diatoms grow at elevated Si:C and Si:N ratios and should be efficiently exported as particles significantly enriched in Si relative to C. However, Fe limitation also alters diatoms species composition and the high Si demand imposed by low Fe can drive HNLC regions to Si limitation or Si/Fe co-limitation. Thus, the degree of Si and/or Fe stress in HNLC waters can all alter diatom taxonomic composition, the elemental composition of diatom cells, and the path cells follow through the food web ultimately altering diatom carbon export. Within each ecosystem state examined in the EXPORTS program, nutrient biogeochemistry, diatom and phytoplankton community structure, and global diatom gene expression patterns (metatranscriptomics) are characterized in the lit ocean. Nutrient amendment experiments with tracer addition (14C, 32Si) are used to quantify the level of Si and Fe stress being experienced by the phytoplankton and to contextualize taxa-specific metatranscriptome responses for resolving gene expression profiles in the in situ communities.
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Subcellular proteomics for determining iron‐limited remodeling of plastids in the model diatom Thalassiosira pseudonana (Bacillariophyta)
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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- Award ID(s):
- 1756816
- PAR ID:
- 10468861
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Phycology
- Volume:
- 59
- Issue:
- 5
- ISSN:
- 0022-3646
- Format(s):
- Medium: X Size: p. 1085-1099
- Size(s):
- p. 1085-1099
- Sponsoring Org:
- National Science Foundation
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