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Bioelectromagnetism

 

In particular, more recently, Wiltschko et al. (2021) reviewed and speculated that CRY1a appears to

be the most likely receptor molecule for magnetic compass information due to its location in the outer

segments of the UV cones with their clear oil droplets. Tese CRYs could generate free radical pairs,

which play a key role as a kind of “quantum compass” (Hiscock et al., 2016b), and are deeply involved in

the magnetic sense. Tat is, the CRY-dependent magnetoreception is currently proposed to be a result

of light-initiated electron transfer chemistry in the protein, which is magnetically sensitive by virtue of

the RPM (Rodgers and Hore, 2009; Dodson et al., 2013). In the principle of magnetoreception mecha­

nism according to the RPM models, it is not possible to distinguish whether the directions of electron

spins are opposite or the same, so in principle, it is possible to detect the inclination of the magnetic feld

lines, but which is north polarity or south polarity. It is impossible to obtain information on the direc­

tion itself. Terefore, as described above, the quantum compass is an inclination compass that only the

information on the dip angle can be obtained.

In a follow-up study, Bradlaugh et al. (2021) reported that coupling blue light exposure with a 100 mT

static magnetic feld is sufcient to potentiate the efect of activated DmCRY on increasing the fring rate

of action potentials in an identifed motoneuron, termed the anterior corner cell, aCC. Again, no efects

of either blue light or magnetic feld were observed without prior expression of DmCRY or to orange

light (590 nm) (Giachello et al., 2016). Te efect was also abolished under conditions where Kv channels

were blocked, and a similar mechanism was proposed for clock cells requiring HYPERKINETIC (Fogle

et al., 2015). It seems clear that exposure to blue light is a key factor in all assays that have measured

magnetosensitivity (Bradlaugh et al., 2021). Tis raises the exciting possibility that free FAD (blue light-

sensitive favin) may form RPs with available Trp residues in other intracellular proteins (Bradlaugh

et al., 2021). However, a necessity for CRY, or at least the C-terminal, to transduce this efect suggests

that CRY is required for downstream signaling following RP formation, whether this is due to an RP

formed with the Trp of the C-terminal or with those of other unidentifed proteins (Bradlaugh et al.,

2021). In this respect, it is possible that the previously discussed protein-protein interaction domain

located in the C-terminal fragment may provide a nucleation point for further components of this sig­

nal transduction cascade to assemble into a functioning magnetosensory complex (Bradlaugh et al.,

2021). Tus, it is conceivable that CRY functions as an amplifer to boost weak magnetic feld efects that

occur within free FAD (Bradlaugh et al., 2021). A recent study reports that FAD-RPs are magnetic feld-

sensitive at physiological pH (Antill and Woodward, 2018).

As another CRY-related mechanism, Zaporozhan and Ponomarenko (2010) hypothesized that CRY is

a transcriptional repressor of the major circadian complex CLOCK/BMAL1 (reviewed by Langmesser

et al., 2008), and therefore, magnetic felds via some modulation of CRY function can infuence circa­

dian gene expression and modify the activity of the transcription factor nuclear factor-κB (NF-κB)­

and glucocorticoids-dependent signaling pathways. In addition, Zaporozhan and Ponomarenko (2010)

proposed a theory that magnetic felds induce defnite genetic efects due to the existence of magnetic

feld–sensitive transcription factor repressors capable of regulating the biological activity of organisms

through epigenetic mechanisms. Tese substances are proteins of the “CRY-photolyase family.” Radical

pair intermediates were observed in a number of proteins from the CRY-photolyase family using time-

resolved EPR (Gindt et al., 1999; Weber et al., 2002; Biskup et al., 2009; Nohr et al., 2016).

Putative magnetoreceptor, CRY was frst found in a fowering plant Arabidopsis thaliana in 1993

(Ahmad and Cashmore, 1993) termed as AtCRY1, which played an important role in photomorphogenic

responses (Lin and Todo, 2005). Recently, the role of AtCRY1 has been investigated as a candidate for

magnetoreceptor. For example, the growth-inhibiting infuence of blue light on the Arabidopsis thali­

ana is moderated by magnetic felds in a way that may use the RPM (Ahmad et al., 2007). Moreover, the

removal of the local GMF negatively afects the reproductive growth of Arabidopsis, which thus afects

the yield and harvest index (Xu et al., 2012, 2013, 2014b), and delays the fowering time through down-

regulation of fower-related genes (Xu et al., 2012; Agliassa et al., 2018a). Te expression changes of three

AtCRY1-signaling related genes, PHYB, CO, and FT suggest that the efects of a near-null magnetic feld

are CRY-related, which may be revealed by a modifcation of the active state of CRY and the subsequent