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Gene expression response to copper toxicity between coastal and open ocean strains of marine Synechococcus

ABSTRACT: Marine cyanobacteria are thought to be the most sensitive of the phytoplankton groups to copper toxicity, yet little is known of the transcriptional response of marine Synechococcus to copper shock. Global transcriptional response to two levels of copper shock was assayed in both a coastal and an open ocean strain of marine Synechococcus using whole genome expression microarrays. Both strains showed an osmoregulatory-like response, perhaps as a result of increasing membrane permeability. This could have implications for marine carbon cycling if copper shock leads to dissolved organic carbon leakage in Synechococcus. The two strains additionally showed a reduction in photosynthetic gene transcripts. Contrastingly, the open ocean strain showed a typical stress response whereas the coastal strain exhibited a more specific oxidative or heavy metal type response. In addition, the coastal strain activated more regulatory elements and transporters, many of which are not conserved in other marine Synechococcus strains and may have been acquired by horizontal gene transfer. Thus, tolerance to copper shock in some marine Synechococcus may in part be a result of an increased ability to sense and respond in a more specialized manner.

ORGANISM(S): Synechococcus sp. CC9311 Parasynechococcus marenigrum WH 8102

PROVIDER: GSE13910 | GEO | 2009/07/01

SECONDARY ACCESSION(S): PRJNA110327

REPOSITORIES: GEO

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Project description:Proteins secreted by marine cyanobacterium Synechococcus under phosphorus stress is largely uncharacterized. This dataset characterizes the exoproteins for both an open ocean (WH8102) and coastal (WH5701) Synechococcus strain and were collected as part of the study "Dissolved organic phosphorus bond-class utilization by Synechococcus". Study Abstract: Dissolved organic phosphorus (DOP) contains compounds with phosphoester (P-O-C), phosphoanhydride (P-O-P), and phosphorus-carbon (P-C) bonds. Despite DOP’s importance as a nutritional source for marine microorganisms, the bioavailability of each bond-class to the widespread cyanobacterium Synechococcus remains largely unknown. This study evaluates bond-class specific DOP utilization by cultures of an open ocean and a coastal ocean Synechococcus strain. Both strains exhibited comparable growth rates when provided phosphate, short-chain and long-chain polyphosphate (P-O-P), adenosine 5’-triphosphate (P-O-C and P-O-P), and glucose-6-phosphate (P-O-C) as the phosphorus source. However, growth rates on phosphomonoester adenosine 5’-monophosphate (P-O-C) and phosphodiester bis(4-methylumbelliferyl) phosphate (C-O-P-O-C) varied between strains, and neither strain grew on selected phosphonates. Consistent with the growth measurements, both strains preferentially hydrolyzed 3-polyphosphate, followed by adenosine 5’-triphosphate, and then adenosine 5’-monophosphate. The strains’ exoproteome contained phosphorus hydrolases, which combined with enhanced cell-free hydrolysis of 3-polyphosphate and adenosine 5’-triphosphate under phosphate deficiency, suggests active mineralization of short-chain polyphosphate by Synechococcus’ exoproteins. Synechococcus alkaline phosphatases presented broad substrate specificities, including activity towards short-chain polyphosphate, with varying affinities between the two strains. Collectively, these findings underscore the potentially significant role of compounds with phosphoanhydride bonds in Synechococcus phosphorus nutrition, thereby expanding our understanding of microbially-mediated DOP cycling in marine ecosystems.

Project description:We have looked at the transcriptional response of well characterised Synechococcus open ocean (WH8102) and coastal (CC9311) isolates to two DNA damaging agents, mitomycin C and ethidium bromide, using whole genome expression microarrays. The coastal strain, which was able to grow on higher concentrations of both chemicals, showed differential regulation of a larger proportion of its genome following M-bM-^@M-^Xtoxic shockM-bM-^@M-^Y treatment with each agent. Many of the orthologous genes in these strains, including those encoding sensor kinases, showed different transcriptional responses, with the CC9311 genes more likely to show significant changes for each tested treatment. While the overall response of each strain was considerably different, there were distinct transcriptional responses common to both strains observed for each DNA damaging agent, linked to the mode of action of each chemical. In both CC9311 and WH8102 there was evidence of SOS response induction under mitomycin C treatment, with genes encoding recA, the lexA repressor and umuC significantly upregulated in this experiment but not under ethidium bromide treatment. Conversely, ethidium bromide treatment tended to result in upregulation of the DNA-directed RNA polymerase genes, not observed following mitomycin C treatment. Interestingly, a large number of genes residing on putative genomic island regions of each genome also showed significant upregulation under one or both chemical treatments. In this series four conditions have been analyzed. These are 2 hour incubations (shock treatment) with ethidium bromide (EB, final conc 2ug/mL) and mitomycin C (MC, final conc 0.5 ug/mL) for Synechococcus sp. WH8102 and CC9311. For each slide, an experimental RNA sample was labeled with Cy3 or Cy5 and was hybridized with a reference RNA from a control sample (no addition of chemical agent) labeled with the other Cy dye. There are six slides per condition, each with at least two biological replicates and three technical replicates, including at least one flip-dye comparison. Each slide contains six replicate spots per gene.

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Gene expression response to copper toxicity between coastal and open ocean strains of marine Synechococcus

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