Sébastien Girard

High frequency (900 MHz) low amplitude (5 V m−1) electromagnetic field: a genuine environmental stimulus that affects transcription, translation, calcium and energy charge in tomato

Using an especially-designed facility, the Mode Stirred Reverberation Chamber, we exposed tomato plants (Lycopersicon esculentum Mill. VFN8) to low level (900xa0MHz, 5xa0Vxa0m−1) electromagnetic fields for a short period (10xa0min) and measured changes in abundance of three specific mRNA soon after exposure. Within minutes of electromagnetic stimulation, stress-related mRNA (calmodulin, calcium-dependent protein kinase and proteinase inhibitor) accumulated in a rapid, large and 3-phase manner typical of an environmental stress response. Accumulation of these transcripts into the polysomal RNA also took place (indicating that the encoded proteins were translated) but was delayed (indicating that newly-synthesized mRNA was not immediately recruited into polysomes). Transcript accumulation was maximal at normal Ca2+ levels and was depressed at higher Ca2+, especially for those encoding calcium-binding proteins. Removal of Ca2+ (by addition of chelating agents or Ca2+ channel blocker) led to total suppression of mRNA accumulation. Finally, 30xa0min after the electromagnetic treatment, ATP concentration and adenylate energy charge were transiently decreased, while transcript accumulation was totally prevented by application of the uncoupling reagent, CCCP. These responses occur very soon after exposure, strongly suggesting that they are the direct consequence of application of radio-frequency fields and their similarities to wound responses strongly suggests that this radiation is perceived by plants as an injurious stimulus.

Microwave Irradiation Affects Gene Expression in Plants

The physiological impact of non-ionizing radiation has long been considered negligible. However, here we use a carefully calibrated stimulation system that mimics the characteristics (isotropy and homogeneity) of electromagnetic fields present in the environment to measure changes in a molecular marker (mRNA encoding the stress-related bZIP transcription factor), and show that low amplitude, short duration, 900 MHz EMF evokes the accumulation of this mRNA. Accumulation is rapid (peaking 5-15 min after stimulation) and strong (3.5-fold), and is similar to that evoked by injurious stimuli.

Plants Respond to GSM-Like Radiations

In this article, we propose that an organism’s general architecture is of primary importance for its ability to perceive electromagnetic radiation. Animals develop mainly as volumes for internal assimilation and appendages to increase their mobility, while plants develop as surfaces to optimize interaction with the environment. As a consequence, the proportion of cells directly interacting with EMF radiation at the organism interface is much higher in plants than it is in animals, making them especially suited to study EMF effects on life.

A possible role for extra-cellular ATP in plant responses to high frequency, low amplitude electromagnetic field.

In parallel to evoking the accumulation of stress-related transcripts, exposure to low level 900 MHz EMF affected the levels of ATP, the main energy molecule of the cell. Its concentration dropped rapidly (27% after 30 min) in response to EMF exposure, along with a 18% decrease in the adenylate energy charge (AEC), a good marker of cell energy status. One could interpret this decrease in ATP and AEC in a classical way, i.e., as the result of an increase in cellular energy usage, but recent work brings exciting new insights in pointing out a signalling function for ATP, especially in the stress physiology context where it could trigger both reactive oxygen species and calcium movement (this latter being involved in plant responses to EMF exposure). In this addendum, we discuss our results within this new perspective for ATP function.

Uncertainty quantification for electromagnetic propagation in enclosed environments

In most cases, a generic subsystem embedded inside a vehicle or more generally an electronic system may be threatened by intentional transmitters close to it. Cabling and apertures offers major routes by which electromagnetic interference (EMI) will enter a subsystem. Since electronic systems (aeronautical ones for instance) are often subjected to thermal and mechanical random variations, their geometrical structures may become uncertain. Previous works laid emphasis on the importance of propagating these uncertainties via transmission-line method, TLM, (M. Panitz and C. Christopoulos, in Proc. ICEAA, 2012, pp. 182–185). Few studies were achieved to experimentally check the impact of random variables (r.v.s) modeling in EMC framework (D. Thomas et al., in Proc. ESA workshop on EMC, 2012). Figure 1 gives an inner view of the cabinet designed and achieved by EMC group (Institut Pascal) to automate Monte Carlo (MC) the electromagnetic propagation of waves inside the enclosure assuming random geometrical variations due to moving external trap (T), inner moving plate (P) and rotating stirrer (S). Figure 2 shows a set of MC measurements of parameter S21 between emitting MSRC log-periodic antenna and dipole (Fig. 1).

Optimization of experimental procedure in EMC using re-sampling techniques

Recent studies have shown a high interest in statistical methods dedicated to the prediction of the maximum confidence in simulation and measurements for Electromagnetic Compatibility. In particular, it has been shown that one of the main issues remains the access to a number of samples allowing estimating the risks with regard to the test set-up random variables. In this paper it is argued that re-sampling techniques, also called bootstrapping procedures, enable to optimize the number of experiments while estimating the maximum confidence level of the accessible samples.

Paradigm of sensitivity analysis in EMC stochastic enclosed environments

The aim of this contribution is to present a whole experimental methodology to assess the effects of uncertainties for a classical EMC issue. To this end, a cabinet was designed and achieved with controlled geometrical parameters including moving external slot and internal plate, an inner rotating unit embedded with stirrer and cable. From industrial expectations, the experimental setup and the theoretical basis will be described briefly. Then, the validation (convergence, accuracy and robustness) of the proposed stochastic methods will be obtained facing Monte Carlo (MC) measurements including three random parameters. Finally, the combination of stochastic techniques with sensitivity study will improve the global process.

Systemic response after local exposition to low amplitude HF-EMF in tomato plants

Exposing tomato plant to low amplitude high frequency electromagnetic field results in an immediate (15-60 minutes) and strong (3-7 fold) accumulation of stress-related transcripts. These accumulations are systemic, observed in exposed organ (local response) as well as in protected tissue (distant response). Tomato mutants deficient for abscisic acid display only the local response but lack the distant one. We propose that EMF exposition evokes the genesis of an informative signal, dependant upon ABA metabolism, that is rapidly widespread through the plant.