Cryptochromes are flavoprotein photoreceptors first discovered in Arabidopsis thaliana, and subsequently in many organisms, where they mediate important signaling functions. Cryptochrome has also been implicated in plant magneto-sensing that alters growths rates in different magnetic field environments and are potentially involved in avian navigation. In plants they influence de-etiolation, developmental and stress responses resulting from interaction with downstream signaling partners such as transcription factors and components of the proteasome. Recently, the PI has shown that Arabidopsis cry1 activation by blue light results in the direct enzyme conversion of O2 to H2O2 in vitro. Blue-light dependent ROS formation by Arabidopsis cryptochrome may define a novel evolutionarily conserved signaling mechanism.
We propose that cryptochrome photoreceptors respond to appropriate magnetic field strengths by modulation of singlet-triplet state occupancy in spin-correlated radical pairs of flavin semiquinone (FAD⦁) and superoxide (O2⦁-). We hypothesize that ROS radical pairs can affect the outcome of cryptochrome ROS biochemical reactions, influencing intracellular signal transduction cascades and cell–cell communication mechanisms.
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