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Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult C. elegans

ABSTRACT: Reports that low-intensity microwave radiation can induce heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by very slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9-3 mW kg-1 for 6-well plates) that minimises the temperature differential between sham and exposed conditions to ≤ 0.1°C. Comparable measurement and simulation studies of SAR distribution within this exposure system are presented. We compared 5 Affymetrix gene-arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against 5 gene-arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). Few genes showed consistent expression changes across all 5 comparisons, and all such expression changes appeared modest after applying standard normalisation procedures (≤ 30% up- or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131). As one example, an apparent up-regulation of the vit-3 vitellogenin gene by microwave exposure was not mirrored by similar changes affecting the other co-regulated members of the same vit gene family. We conclude that the pattern of gene expression in L4/adult C elegans is not substantially perturbed by low-intensity microwave radiation, and that the minor changes observed in this study may well be explicable as false positives. As a check on the sensitivity of the Affymetrix gene-arrays used, we also compared RNA samples from N2 worms subjected to a sub-heat-shock treatment (28ºC) against controls kept at 26 ºC (but using only 2 gene arrays per condition). After similar normalisation, many more genes (3712) showed substantial expression changes (i.e. > 2-fold at p < 0.05), including a group of six heat-shock genes which were strongly but unexpectedly down-regulated (by > 10-fold). However, further replication and confirmation by real-time RT-PCR would be needed to establish how many of these changes might also be false positives. Experimenter name: Adam Dawe Experimenter phone: +27 21 959 2364 adam@sanbi.ac.za Experimenter institute: South African National Bioinformatics Institute Experimenter address: University of Western Cape, Old Chemistry Building, University of Western Cape, Modderdam Road, Bellville 7530, Capetown Experimenter zip/postal_code: 7530 Experimenter country: South Africa Keywords: Microwave radiation, gene expression, gene arrays, Caenorhabditis elegans

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE10787 | GEO | 2009/03/12

SECONDARY ACCESSION(S): PRJNA107477

REPOSITORIES: GEO

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Project description:Reports that low-intensity microwave radiation can induce heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by very slight heating. This study used a microwave exposure system (1.0 GHz, 0.5 W power input; SAR 0.9-3 mW kg-1 for 6-well plates) that minimises the temperature differential between sham and exposed conditions to ≤ 0.1°C. Comparable measurement and simulation studies of SAR distribution within this exposure system are presented. We compared 5 Affymetrix gene-arrays of pooled triplicate RNA populations from sham-exposed L4/adult worms against 5 gene-arrays of pooled RNA from microwave-exposed worms (taken from the same source population in each run). Few genes showed consistent expression changes across all 5 comparisons, and all such expression changes appeared modest after applying standard normalisation procedures (≤ 30% up- or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131). As one example, an apparent up-regulation of the vit-3 vitellogenin gene by microwave exposure was not mirrored by similar changes affecting the other co-regulated members of the same vit gene family. We conclude that the pattern of gene expression in L4/adult C elegans is not substantially perturbed by low-intensity microwave radiation, and that the minor changes observed in this study may well be explicable as false positives. As a check on the sensitivity of the Affymetrix gene-arrays used, we also compared RNA samples from N2 worms subjected to a sub-heat-shock treatment (28ºC) against controls kept at 26 ºC (but using only 2 gene arrays per condition). After similar normalisation, many more genes (3712) showed substantial expression changes (i.e. > 2-fold at p < 0.05), including a group of six heat-shock genes which were strongly but unexpectedly down-regulated (by > 10-fold). However, further replication and confirmation by real-time RT-PCR would be needed to establish how many of these changes might also be false positives. Experimenter name: Adam Dawe; Experimenter phone: +27 21 959 2364; adam@sanbi.ac.za; Experimenter institute: South African National Bioinformatics Institute; Experimenter address: University of Western Cape, Old Chemistry Building, University of Western Cape, Modderdam Road, Bellville 7530, Capetown; Experimenter zip/postal_code: 7530; Experimenter country: South Africa Experiment Overall Design: 14 samples were used in this experiment

Project description:In the absence of adaptive immunity displayed by animals, plants respond locally to biotic challenge via inducible basal defense networks activated through recognition and response toconserved pathogen associated molecular patterns (PAMPs). In addition, immunity can be induced in tissues remote from infection sites via systemic acquired resistance (SAR), initiated following gene-for-gene recognition between plant resistance proteins and microbial effectors.The nature of the mobile signal and remotely activated networks responsible for establishing SAR remain unclear. Here we show that despite the absence of PAMP contact, systemically responding leaves rapidly activate a SAR transcriptional signature with strong similarity to local basal defense. Jasmonates have previously been implicated in systemic signalling in response to wounding and plant herbivory but not SAR. We present several lines of evidence that suggest jasmonates may also be central to SAR. Jasmonic acid (JA) rapidly accumulates in phloem exudates of leaves challenged with an avirulent strain of Pseudomonas syringae. In systemically responding leaves transcripts associated with jasmonate biosynthesis are upregulated and JA increases transiently. SAR can be mimicked by foliar JA application and is abrogated in mutants impaired in jasmonate synthesis or response. We conclude that, jasmonate signalling appears to mediate long-distance information transmission. Moreover, the systemic transcriptional response shares extraordinary overlap with local herbivory and wounding responses, indicating that jasmonates may be central to an evolutionarily conserved signalling network, which decodes multiple abiotic and biotic stress signals. Experimenter name: William Truman Experimenter phone: +44 (0)1392 263789 Experimenter fax: +44 (0)1392 263434 Experimenter address: School of Biosciences Experimenter address: Geoffrey Pope Building Experimenter address: Stocker Road Experimenter address: Exeter Experimenter address: Devon Experimenter zip/postal_code: EX4 4QD Experimenter country: UK Keywords: infection

Project description:In the absence of adaptive immunity displayed by animals, plants respond locally to biotic challenge via inducible basal defense networks activated through recognition and response toconserved pathogen associated molecular patterns (PAMPs). In addition, immunity can be induced in tissues remote from infection sites via systemic acquired resistance (SAR), initiated following gene-for-gene recognition between plant resistance proteins and microbial effectors.The nature of the mobile signal and remotely activated networks responsible for establishing SAR remain unclear. Here we show that despite the absence of PAMP contact, systemically responding leaves rapidly activate a SAR transcriptional signature with strong similarity to local basal defense. Jasmonates have previously been implicated in systemic signalling in response to wounding and plant herbivory but not SAR. We present several lines of evidence that suggest jasmonates may also be central to SAR. Jasmonic acid (JA) rapidly accumulates in phloem exudates of leaves challenged with an avirulent strain of Pseudomonas syringae. In systemically responding leaves transcripts associated with jasmonate biosynthesis are upregulated and JA increases transiently. SAR can be mimicked by foliar JA application and is abrogated in mutants impaired in jasmonate synthesis or response. We conclude that, jasmonate signalling appears to mediate long-distance information transmission. Moreover, the systemic transcriptional response shares extraordinary overlap with local herbivory and wounding responses, indicating that jasmonates may be central to an evolutionarily conserved signalling network, which decodes multiple abiotic and biotic stress signals. Experimenter name: William Truman; Experimenter phone: +44 (0)1392 263789; Experimenter fax: +44 (0)1392 263434; Experimenter address: School of Biosciences; Experimenter address: Geoffrey Pope Building; Experimenter address: Stocker Road; Experimenter address: Exeter; Experimenter address: Devon; Experimenter zip/postal_code: EX4 4QD; Experimenter country: UK Experiment Overall Design: 9 samples were used in this experiment

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Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult C. elegans

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