Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of Dictyostelium discoides mutant cell type aspidocyte induced by heavy meatals and antibiotics

ABSTRACT: We describe the serendipitous discovery and first characterization of a new resistant cell type from Dictyostelium, which we propose to call the aspidocyte (aspida: Greek for shield). These cells are induced from amoebae by a range of toxins including heavy metals and antibiotics, and were first detected by their striking resistance to detergent lysis. Aspidocytes are separate, rounded or irregular shaped cells that are immotile but remain fully viable; once the toxic stress is removed, they revert to amoeboid cells within an hour. Induction takes a few hours and is completely blocked by the protein synthesis inhibitor cycloheximide. Aspidocytes lack a cell wall and their resistance to detergent lysis is active, requiring continued energy metabolism, and may be assisted by a complete cessation of endocytosis, as measured by uptake of the dye FM1-43. Microarray analysis shows that aspidocytes have a distinct pattern of gene expression with a number of genes up-regulated that are predicted to be involved in lipid metabolism. Aspidocytes were initially detected in a hypersensitive mutant, in which the AMP deaminase gene is disrupted, suggesting that the inductive pathway involves AMP levels or metabolism. Since aspidocytes can also be induced from wild-type cells and are much more resistant than amoebae to a membrane disrupting antibiotic, it is possible that they are an adaptation allowing Dictyostelium cells to survive a sudden onslaught of toxins in the wild.

ORGANISM(S): Dictyostelium discoideum

SUBMITTER: Matloob Qureshi

PROVIDER: E-SGRP-5 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

A new environmentally resistant cell type from Dictyostelium.

Serafimidis Ioannis I Bloomfield Gareth G Skelton Jason J Ivens Al A Kay Robert R RR

Microbiology (Reading, England) 20070201 Pt 2

This paper describes the serendipitous discovery and first characterization of a new resistant cell type from Dictyostelium, for which the name aspidocyte (from aspis: Greek for shield) is proposed. These cells are induced from amoebae by a range of toxins including heavy metals and antibiotics, and were first detected by their striking resistance to detergent lysis. Aspidocytes are separate, rounded or irregular-shaped cells, which are immotile but remain fully viable; once the toxic stress is ...[more]

PMID: 17259634

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Project description:The genome of the marine Synechococcus sp. WH8102 displays a minimal regulatory network yet physiological and molecular responses of this organism are tuned to episodic limitation for nitrogen and phosphorus. Microarray analyses have demonstrated a key role for the two-component regulatory system, PhoBR, in the regulation of P transport and metabolism in this strain. However, there is some evidence that another regulator, SYNW1019 (designated as ptrA), probably under the control of PhoB, is involved in the wider response to P-depletion. PtrA is one of only two genome encoded DNA binding proteins of the CRP family in Synechococcus sp. WH8102, and a potential transcriptional regulator with homology to NtcA, the global nitrogen regulator in cyanobacteria. To define the precise role of this regulator we constructed a mutant by insertional inactivation and compared the physiology of wild-type Synechcococcus sp. WH8102 with the ptrA mutant under P-replete and P-deplete growth conditions. During P-depletion the ptrA mutant failed to up-regulate phosphatase activity. Microarrays and quantitative RT-PCR indicate that a subset of the Pho regulon is directly controlled by PtrA, including two phosphatase genes (SYNW0196, SYNW2390), a predicted phytase (SYNW0762) and a gene of unknown function (SYNW0165) all of which are highly up regulated during P-limitation. This result was confirmed by electrophoretic mobility shift assays which demonstrated binding of over expressed PtrA to promoter sequences upstream of the induced phosphatases (SYNW0165, SYNW0196 and SYNW2390). This work suggests a two-tiered response to P-depletion in this strain, the first being PhoB-dependent induction of high affinity PO4 transporters, and the second the PtrA-dependent induction of phosphatases for scavenging organic P. The levels of numerous other transcripts are also directly or indirectly controlled by PtrA, including those involved in cell surface modification, metal uptake, photosynthesis, stress responses and other metabolic process, which may indicate a wider role for PtrA in cellular organisation. In an environmental context ptrA is found in a number of picocyanobateria isolated from a range of oceanic provinces, including strains that lack a functional phoBR..These results give broader insight into the regulation of physiological responses that may dictate niche adaptation in genetically diverse lineages of marine Synechococcus, and suggest that signalling networks and coordinated responses to nutrient availability are important, even in oligotrophic ocean environments. In this series gene expression of a ptrA mutant has been analyzed under phosphorus deplete conditions just after the onset of induction of phosphatase activity in wild type. There are six duel-channel slides upon which both ptrA mutant and wild type samples were hybridized. There are three technical replicates for each of two biological replicates including one flip-dye comparison. Each slide contains six replicate spots per gene.

Dataset Information

Transcription profiling of Dictyostelium discoides mutant cell type aspidocyte induced by heavy meatals and antibiotics

Publications

A new environmentally resistant cell type from Dictyostelium.

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