Magnetic intensity affects cryptochrome-dependent responses in Arabidopsis thaliana

Abstract

Cryptochromes are blue-light absorbing photoreceptors found in many organisms where they have been involved in numerous growth, developmental, and circadian responses. In Arabidopsis thaliana, two cryptochromes, CRY1 and CRY2, mediate several blue-light-dependent responses including hypocotyl growth inhibition. Our study shows that an increase in the intensity of the ambient magnetic field from 33-44 to 500 muT enhanced growth inhibition in A. thaliana under blue light, when cryptochromes are the mediating photoreceptor, but not under red light when the mediating receptors are phytochromes, or in total darkness. Hypocotyl growth of Arabidopsis mutants lacking cryptochromes was unaffected by the increase in magnetic intensity. Additional cryptochrome-dependent responses, such as blue-light-dependent anthocyanin accumulation and blue-light-dependent degradation of CRY2 protein, were also enhanced at the higher magnetic intensity. These findings show that higher plants are sensitive to the magnetic field in responses that are linked to cryptochrome-dependent signaling pathways. Because cryptochromes form radical pairs after photoexcitation, our results can best be explained by the radical-pair model. Recent evidence indicates that the magnetic compass of birds involves a radical pair mechanism, and cryptochrome is a likely candidate for the avian magnetoreception molecule. Our findings thus suggest intriguing parallels in magnetoreception of animals and plants that appear to be based on common physical properties of photoexcited cryptochromes.

Chemical magnetoreception in birds: The radical pair mechanism

“…Similar observations, of a radical pair comprising the FADH • radical and the neutral radical form of the terminal Trp residue of the Trp-triad, have recently been reported for a Cry-DASH protein (102). Furthermore, a small (3-4%) effect of a relatively strong magnetic field (39 mT) on the radical pair recombination kinetics has been found for Escherichia coli photolyase (103) Further evidence for the involvement of cryptochromes has come from experiments on plants (104). Enhanced cryptochrome-mediated blue-light responses in A. thaliana seedlings grown in a 500-T magnetic field have been observed, including a Ϸ30% inhibition of hypocotyl (stem) growth.…”

Physics of life: The dawn of quantum biology

“…Not only birds, but also some insects and even plants show physiological responses to magnetic fields -for example, the growth-inhibiting influence of blue light on the flowering plant Arabidopsis thaliana is moderated by magnetic fields in a way that may also use the radicalpair mechanism 11 . But for clinching proof that it works this way, says Benjamin, "we need to understand the basic molecules involved, and then study them in the lab".…”

A metal left spinning

“…The deep biosphere is large, and, at least in aggregate, it is 'alive' 10,11 . The data almost defy imagination -on the order of a million cells in every cubic centimetre of sediment buried half a kilometre below the sea floor, or more than 50% of all microbial cells on Earth 12 10,11,13 , and a hung jury has been declared 14 over the question of the predominance of Bacteria or Archaea.…”

“…These include approaches that detect ribosomal RNA (rRNA) or intact polar lipids (IPLs) of cell membranes (both are proxies for live cells), or that quantify rRNA gene copies from extracted DNA. Of these techniques, in situ fluorescent tagging of ribosomes in methods known as FISH or CARD-FISH produce the most disparate (indeed, opposite) results 10,11,13 . Although potentially an ideal …”