Nitrogen cost minimization is promoted by structural changes in the transcriptome of N-deprived Prochlorococcus cells.

TitleNitrogen cost minimization is promoted by structural changes in the transcriptome of N-deprived Prochlorococcus cells.
Publication TypeJournal Article
Year of Publication2017
AuthorsRead, RW, Berube, PM, Biller, SJ, Neveux, I, Cubillos-Ruiz, A, Chisholm, SW, Grzymski, JJ
JournalISME J
Volume11
Issue10
Pagination2267-2278
Date Published2017 Oct
ISSN1751-7370
Abstract

Prochlorococcus is a globally abundant marine cyanobacterium with many adaptations that reduce cellular nutrient requirements, facilitating growth in its nutrient-poor environment. One such genomic adaptation is the preferential utilization of amino acids containing fewer N-atoms, which minimizes cellular nitrogen requirements. We predicted that transcriptional regulation might further reduce cellular N budgets during transient N limitation. To explore this, we compared transcription start sites (TSSs) in Prochlorococcus MED4 under N-deprived and N-replete conditions. Of 64 genes with primary and internal TSSs in both conditions, N-deprived cells initiated transcription downstream of primary TSSs more frequently than N-replete cells. Additionally, 117 genes with only an internal TSS demonstrated increased internal transcription under N-deprivation. These shortened transcripts encode predicted proteins with an average of 21% less N content compared to full-length transcripts. We hypothesized that low translation rates, which afford greater control over protein abundances, would be beneficial to relatively slow-growing organisms like Prochlorococcus. Consistent with this idea, we found that Prochlorococcus exhibits greater usage of glycine-glycine motifs, which causes translational pausing, when compared to faster growing microbes. Our findings indicate that structural changes occur within the Prochlorococcus MED4 transcriptome during N-deprivation, potentially altering the size and structure of proteins expressed under nutrient limitation.

DOI10.1038/ismej.2017.88
Alternate JournalISME J
PubMed ID28585937
PubMed Central IDPMC5607370