Reduction of geomagnetic field (GMF) to near null magnetic field (NNMF) affects some Arabidopsis thaliana clock genes amplitude in a light independent manner

Plant endogenous clock consists of self-sustained interlocked transcriptional/translational feedback loops whose oscillation regulates many circadian processes, including gene expression. Its free running rhythm can be entrained by external cues, which can influence all clock parameters. Among external cues, the geomagnetic field (GMF) has been demonstrated to influence plant growth and development. We evaluated the quantitative expression (qRT-PCR) of three clock genes (LHY, GI and PRR7) in time-course experiments under either continuous darkness (CD) or long days (LD) conditions in Arabidopsis thaliana seedlings exposed to GMF (∼40 μT) and Near Null Magnetic Field (NNMF; ∼40 nT) conditions. Under both LD and CD conditions, reduction of GMF to NNMF prompted a significant increase of the gene expression of LHY and PRR7, whereas an opposite trend was found for GI gene expression. Exposure of Arabidopsis to NNMF altered clock gene amplitude, regardless the presence of light, by reinforcing the morning loop. Our data are consistent with the existence of a plant magnetoreceptor that affects the Arabidopsis endogenous clock.

Reduction of geomagnetic field (GMF) to near null magnetic field (NNMF) affects Arabidopsis thaliana root mineral nutrition

The Earth magnetic field (or geomagnetic field, GMF) is a natural component of our planet and variations of the GMF are perceived by plants with a still uncharacterized magnetoreceptor. The purpose of this work was to assess the effect of near null magnetic field (NNMF, ∼40 nT) on Arabidopsis thaliana Col0 root ion modulation. A time-course (from 10 min to 96 h) exposure of Arabidopsis to NNMF was compared to GMF and the content of some cations (NH₄⁺, K⁺, Ca²⁺ and Mg²⁺) and anions (Cl^-, SO₄⁼, NO₃^- and PO₄⁼) was evaluated by capillary electrophoresis. The expression of several cation and anion channel- and transporter-related genes was assessed by gene microarray. A few minutes after exposure to NNMF, Arabidopsis roots responded with a significant change in the content and gene expression of all nutrient ions under study, indicating the presence of a plant magnetoreceptor that responds immediately to MF variations by modulating channels, transporters and genes involved in mineral nutrition. The response of Arabidopsis to reduced MF was a general reduction of plant ion uptake and transport. Our data suggest the importance to understand the nature and function of the plant magnetoreceptor for future space programs involving plant growth in environments with a reduced MF.