Quantitative Proteomics Shows Extensive Remodeling Induced by Nitrogen Limitation in <i>Prochlorococcus marinus</i> SS120

Agustina Dominguez-Martin, Maria, Gomez-Baena, Guadalupe ORCID: 0000-0003-3796-3874, Diez, Jesus, Jose Lopez-Grueso, Maria, Beynon, Robert J ORCID: 0000-0003-0857-495X and Manuel Garcia-Fernandez, Jose
(2017) Quantitative Proteomics Shows Extensive Remodeling Induced by Nitrogen Limitation in <i>Prochlorococcus marinus</i> SS120. MSYSTEMS, 2 (3). e00008-e00017.

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<i>Prochlorococcus</i> requires the capability to accommodate to environmental changes in order to proliferate in oligotrophic oceans, in particular regarding nitrogen availability. A precise knowledge of the composition and changes in the proteome can yield fundamental insights into such a response. Here we report a detailed proteome analysis of the important model cyanobacterium <i>Prochlorococcus marinus</i> SS120 after treatment with azaserine, an inhibitor of ferredoxin-dependent glutamate synthase (GOGAT), to simulate extreme nitrogen starvation. In total, 1,072 proteins, corresponding to 57% of the theoretical proteome, were identified-the maximum proteome coverage obtained for any <i>Prochlorococcus</i> strain thus far. Spectral intensity, calibrated quantification by the Hi3 method, was obtained for 1,007 proteins. Statistically significant changes (<i>P</i> value of <0.05) were observed for 408 proteins, with the majority of proteins (92.4%) downregulated after 8 h of treatment. There was a strong decrease in ribosomal proteins upon azaserine addition, while many transporters were increased. The regulatory proteins P<sub>II</sub> and PipX were decreased, and the global nitrogen regulator NtcA was upregulated. Furthermore, our data for <i>Prochlorococcus</i> indicate that NtcA also participates in the regulation of photosynthesis. <i>Prochlorococcus</i> responds to the lack of nitrogen by slowing down translation, while inducing photosynthetic cyclic electron flow and biosynthesis of proteins involved in nitrogen uptake and assimilation. <b>IMPORTANCE</b><i>Prochlorococcus</i> is the most abundant photosynthetic organism on Earth, contributing significantly to global primary production and playing a prominent role in biogeochemical cycles. Here we study the effects of extreme nitrogen limitation, a feature of the oligotrophic oceans inhabited by this organism. Quantitative proteomics allowed an accurate quantification of the <i>Prochlorococcus</i> proteome, finding three main responses to nitrogen limitation: upregulation of nitrogen assimilation-related proteins, including transporters; downregulation of ribosome proteins; and induction of the photosystem II cyclic electron flow. This suggests that nitrogen limitation affects a range of metabolic processes far wider than initially believed, with the ultimate goal of saving nitrogen and maximizing the nitrogen uptake and assimilation capabilities of the cell.

Item Type: Article
Uncontrolled Keywords: marine cyanobacteria, nitrogen limitation, nitrogen metabolism, prochlorococcus, quantitative proteomics
Depositing User: Symplectic Admin
Date Deposited: 09 Aug 2017 06:47
Last Modified: 13 Feb 2024 15:04
DOI: 10.1128/mSystems.00008-17
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3008875