Unknown,Transcriptomics,Genomics,Proteomics

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Experimental identification of small non-coding RNAs in the model marine bacterium Ruegeria pomeroyi DSS-3

ABSTRACT: In oligotrophic ocean waters where bacteria are often subjected to chronic nutrient limitation, community transcriptome sequencing has pointed to the presence of highly abundant small RNAs (sRNAs). The role of sRNAs in regulating response to nutrient stress was investigated in a model heterotrophic marine bacterium Ruegeria pomeroyi grown in continuous culture under carbon and nitrogen limitation. RNAseq analysis identified 98 sRNAs, of which 69 were cis-encoded and located antisense to their target genes, and 30 were trans-encoded and linked to predicted target genes through complementarity analysis. The most prevalent functional roles of target genes were transport, cell-cell interactions, signal transduction, and transcriptional regulation. Thirty-two percent of the sRNAs had been identified in a previous study of R. pomeroyi growth on organic sulfur compounds, and may be constitutively expressed, while 69% were not identified in previous studies. Eighty-six percent and were transcribed equally under both carbon and nutrient limitation, and may be involved in a general stress response; 14% were differentially regulated under carbon versus nitrogen stress, and may respond to specific nutrient limitations. A network analysis of the predicted target genes of the R. pomeroyi sRNAs indicated that they average fewer connections than typical protein-encoding genes, and appear to be more important in peripheral or niche-defining functions encoded in the pan genome rather than central metabolism encoded in the core genome.

INSTRUMENT(S): AB SOLiD 4 System

ORGANISM(S): Ruegeria pomeroyi DSS-3

SUBMITTER: Adam Rivers

PROVIDER: E-MTAB-4468 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Here, we examined the ramifications of between-species diversity by documenting the transcriptional response of three marine diatoms - Thalassiosira pseudonana, Fragilariopsis cylindrus, and Pseudo-nitzschia multiseries - to the onset of nitrate limitation of growth, a common limiting nutrient in the ocean. Less than 5% of orthologous genes, shared across the three diatoms, displayed the same transcriptional responses across species when growth was limited by nitrate availability. Orthologs, such as those involved in nitrogen uptake and assimilation, as well as carbon metabolism, were differently expressed across the three species. The two pennate diatoms, F. cylindrus and P. multiseries, shared 3,839 clusters without orthologs in the genome of the centric diatom T. pseudonana. A majority of these pennate-clustered genes, as well as the non-orthologous genes in each species, had minimal annotation information, but were often significantly differentially expressed under nitrate limitation, indicating their potential importance in the response to nitrogen availability. Despite these variations in the specific transcriptional response of each diatom, overall transcriptional patterns suggested that all three diatoms displayed a common physiological response to nitrate limitation that consisted of a general reduction in carbon fixation and carbohydrate and fatty acid metabolism and an increase in nitrogen recycling. Transcriptomes were collected for diatom cultures harvested at the onset of stationary phase in low nitrate media (55 M-NM-<M NaNO3, 212 M-NM-<M Na2SiO3, 72.4 M-NM-<M NaH2PO4) or during mid-exponential growth in nutrient-replete media (882 M-NM-<M NaNO3, 106 M-NM-<M Na2SiO3, 36.2 M-NM-<M NaH2PO4) in artificial seawater, maintaining three biological replicates per condition and per diatom (N=18). The SOLiD sequencer (version 4) was used to generate the transcriptomes and the SEAStAR software package was used to process the SOLiD reads and to calculate gene counts. Pooled counts for the nitrate-limited treatment were normalized to pooled counts for the nutrient-replete M-bM-^@M-^\controlM-bM-^@M-^] treatment to generate log fold changes in gene transcription using the R software package edgeR from Bioconductor.

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Experimental identification of small non-coding RNAs in the model marine bacterium Ruegeria pomeroyi DSS-3

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