Dataset Information

Computational prediction of the osmoregulation network in Synechococcus sp. WH8102.

ABSTRACT: BACKGROUND: Osmotic stress is caused by sudden changes in the impermeable solute concentration around a cell, which induces instantaneous water flow in or out of the cell to balance the concentration. Very little is known about the detailed response mechanism to osmotic stress in marine Synechococcus, one of the major oxygenic phototrophic cyanobacterial genera that contribute greatly to the global CO2 fixation. RESULTS: We present here a computational study of the osmoregulation network in response to hyperosmotic stress of Synechococcus sp strain WH8102 using comparative genome analyses and computational prediction. In this study, we identified the key transporters, synthetases, signal sensor proteins and transcriptional regulator proteins, and found experimentally that of these proteins, 15 genes showed significantly changed expression levels under a mild hyperosmotic stress. CONCLUSIONS: From the predicted network model, we have made a number of interesting observations about WH8102. Specifically, we found that (i) the organism likely uses glycine betaine as the major osmolyte, and others such as glucosylglycerol, glucosylglycerate, trehalose, sucrose and arginine as the minor osmolytes, making it efficient and adaptable to its changing environment; and (ii) sigma38, one of the seven types of sigma factors, probably serves as a global regulator coordinating the osmoregulation network and the other relevant networks.

SUBMITTER: Mao X

PROVIDER: S-EPMC2874817 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Computational prediction of the osmoregulation network in Synechococcus sp. WH8102.

Mao Xizeng X Olman Victor V Stuart Rhona R Paulsen Ian T IT Palenik Brian B Xu Ying Y

BMC genomics 20100510

<h4>Background</h4>Osmotic stress is caused by sudden changes in the impermeable solute concentration around a cell, which induces instantaneous water flow in or out of the cell to balance the concentration. Very little is known about the detailed response mechanism to osmotic stress in marine Synechococcus, one of the major oxygenic phototrophic cyanobacterial genera that contribute greatly to the global CO2 fixation.<h4>Results</h4>We present here a computational study of the osmoregulation ne ...[more]

PMID: 20459751

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Project description:Primary productivity of open ocean environments, such as those inhabited by marine picocyanobacteria Synechococcus sp.WH8102, are often limited by low inorganic phosphate (P). To observe how this organism copes with P starvation, we constructed a full genome microarray and examined differences in gene expression under P-limited and P-replete growth conditions. To determine the temporal nature of the responses, comparisons were made for cells newly entered into P-stress (at a time point corresponding to the induction of extracellular alkaline phosphatase activity) and a later time point (late log phase). In almost all instances the P starvation response was transitory, with 36 genes showing significant upregulation (>log2 fold) while 23 genes were highly downregulated at the early time point; however, these changes in expression were maintained for only five of the upregulated genes. Knockout mutants were constructed for genes SYNW0947 or SYNW0948, comprising a two component regulator hypothesized to play a key role in regulating the response to P-limitation. A high degree of overlap in the sets of genes affected by P-limited conditions and in the knockout mutants supports this hypothesis; however there is some indication that other regulators may play a role in this response in Synechococcus sp. WH8102. Consistent with what has been observed in many other cyanobacteria, the Pho regulon of this strain is comprised largely of genes for alkaline phosphatases, P transport or P metabolism. Interestingly, however, the exact composition and arrangement of the Pho regulon appears highly variable in marine cyanobacteria. In this series four conditions have been analyzed. These are low phosphate stress during early log phase, low phosphate stress during late log phase, SYNW0947 mutation, and SYNW0948 mutation. There are six slides per condition, each with two biological replicates. There are three technical replicates for each biological replicate including one flip-dye comparison. The exception is the low phosphate stress during late log phase experiment which has a total of five slides, two biological replicates with three and two technical replicates, respectively, and one flip-dye comparison for each biological replicate. Each slide contains six replicate spots per gene.

Project description:Phosphorus, a vital macronutrient, often limits primary productivity in marine environments. Marine Synechococcus strains, including WH8102, rely on high-affinity phosphate-binding proteins (PstS) to scavenge inorganic phosphate in oligotrophic oceans. However, WH8102 possesses three distinct PstS homologs whose substrate specificity and ecological roles are unclear. The three PstS homologs were heterologously expressed and purified to investigate their substrate specificity and binding kinetics. Our study revealed that all three PstS homologs exhibited a high degree of specificity for phosphate but differed in phosphate binding affinities. Notably, PstS1b displayed nearly 10-fold higher binding affinity (KD = 0.44 µM) compared to PstS1a (KD = 3.3 μM) and PstS2 (KD = 4.3 μM). Structural modeling suggested a single amino acid variation in the binding pocket of PstS1b (threonine instead of serine in PstS1a and PstS2) likely contributed to its higher Pi affinity. Genome context data, together with the protein biophysical data, suggest distinct ecological roles for the three PstS homologs. We propose that PstS1b may be involved in scavenging inorganic phosphorus in oligotrophic conditions and that PstS1a may be involved in transporting recycled phosphate derived from organic phosphate cleavage. The role of PstS2 is less clear, but it may be involved in phosphate uptake when environmental phosphate concentrations are transiently higher. The conservation of three distinct PstS homologs in Synechococcus clade III strains likely reflects distinct adaptations for P acquisition under varying oligotrophic conditions.IMPORTANCEPhosphorus is an essential macronutrient that plays a key role in marine primary productivity and biogeochemistry. However, intense competition for bioavailable phosphorus in the marine environment limits growth and productivity of ecologically important cyanobacteria. In oligotrophic oceans, marine Synechococcus strains, like WH8102, utilize high-affinity phosphate-binding proteins (PstS) to scavenge inorganic phosphate. However, WH8102 possesses three distinct PstS homologs, with unclear substrate specificity and ecological roles, creating a knowledge gap in understanding phosphorus acquisition mechanisms in picocyanobacteria. Through genomic, functional, biophysical, and structural analysis, our study unravels the ecological functions of these homologs. Our findings enhance our understanding of cyanobacterial nutritional uptake strategies and shed light on the crucial role of these conserved nutrient uptake systems in adaptation to specific niches, which ultimately underpins the success of marine Synechococcus across a diverse array of marine ecosystems.

Dataset Information

Computational prediction of the osmoregulation network in Synechococcus sp. WH8102.

Publications

Computational prediction of the osmoregulation network in Synechococcus sp. WH8102.

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