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Transcriptional changes measured in rice roots after exposure to arsenite-contaminated sediments.

ABSTRACT: Transcriptional analyses are discussed to provide a deeper understanding of the molecular mechanisms underlying toxic effects. Thus, they can complement classic ecotoxicological test methods and potentially allow the identification of biomarkers associated to the exposure of chemical stressors and or adverse biological effects. This feasibility study intended to identify a set of potential gene expression biomarkers for arsenite-exposure in rice roots that could complement the informative value of an existing sediment-contact test with rice. A sediment-contact test with Oryza sativa with the parameters inhibition of root and shoot elongation as phenotypic endpoints was used as basis. Rice plants were exposed to arsenite-spiked sediments. Transcriptomic changes in response to arsenite were observed by means of cDNA-microarray analysis regarding the whole-transcriptome at two sublethal arsenite concentrations. In order to identify candidate biomarker genes, differentially expressed genes were identified. Arsenite-induced differentially expressed genes were significantly associated with gene ontology (GO)-terms that indicated a general stress response. Of the differentially expressed genes, five genes were selected and their expression was measured at seven arsenite concentrations by means of qPCR in order to obtain their expression profiles. Three candidate biomarker genes showed a dose-dependent upregulation, while two showed no clear dose-dependent expression. The expression of all candidate biomarkers was also assessed in rice plants grown on two arsenic-contaminated natural sediments, but only one biomarker gene showed the expected upregulation.

SUBMITTER: Brinke A

PROVIDER: S-EPMC5773613 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Transcriptional changes measured in rice roots after exposure to arsenite-contaminated sediments.

Brinke Alexandra A Reifferscheid Georg G Klein Roland R Feiler Ute U Buchinger Sebastian S

Environmental science and pollution research international 20171113 3

Transcriptional analyses are discussed to provide a deeper understanding of the molecular mechanisms underlying toxic effects. Thus, they can complement classic ecotoxicological test methods and potentially allow the identification of biomarkers associated to the exposure of chemical stressors and or adverse biological effects. This feasibility study intended to identify a set of potential gene expression biomarkers for arsenite-exposure in rice roots that could complement the informative value ...[more]

PMID: 29134529

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Project description:We analyzed the transcriptional response of the actinomycete Rhodococcus aetherivorans I24 to biphenyl and polychlorinated biphenyls (PCBs). This species has not been extensively exposed to PCBs, as it was first isolated from a toluene contaminated aquifer, rather than a site contaminated with polychlorinated hydrocarbons. Using a microarray targeting 3524 genes, we assessed gene expression in minimal medium supplemented with various substrates (e.g. PCBs) and in both PCB-contaminated and non-contaminated sediment slurries. Relative to the reference condition (minimal medium supplemented with glucose), 408 genes were up-regulated in the various treatments. In medium and in sediment, PCBs elicited the up-regulation of a common set of 100 genes, including chaperones (groEL), a superoxide dismutase (sodA), alkyl hydroperoxide reductase protein C (ahpC), and a catalase/peroxidase (katG). Analysis of the R. aetherivorans I24 genome sequence identified orthologs of many of the genes in the canonical biphenyl pathway, but very few of these genes were up-regulated in response to PCBs or biphenyl. This study is one of the first which utilizes microarrays to assess the transcriptional response of a soil bacterium to a pollutant under conditions which more closely resemble the natural environment. Our results indicate that the transcriptional response of R. aetherivorans I24 to PCBs, in both medium and sediment, is primarily directed towards reducing oxidative stress, rather than catabolism. In addition, the identification of numerous genes expressed in contaminated soil specifically may have implications for the development of biosensors. Finally, comparative genomic and transcriptomic analyses suggest that the mere presence of orthologs of the required enzymes may not be sufficient to confer a vigorous biphenyl/PCB metabolism. RNA was isolated from cells incubated in the following: sediment from a PCB-contaminated industrial site, uncontaminated sediment from a comparable site, and defined media supplemented with glucose (3 g/L), glucose and biphenyl (3 g/L, 4.5 Î¼M), or glucose and PCBs (3 g/L, 5 mg/L Aroclor 1254). In all cases, there were 3 biological replicates and 2 technical replicates (repeat hybridizations). A total of 3524 genes are represented on the arrays; of these, 41 and 176 are found on the plasmids pRA2 and pRA3, respectively. On average, there are 3 distinct 24nt probes per gene.

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Transcriptional changes measured in rice roots after exposure to arsenite-contaminated sediments.

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Transcriptional changes measured in rice roots after exposure to arsenite-contaminated sediments.

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