Cryptochrome mediated magnetic sensitivity in Arabidopsis occurs independently of light-induced electron transfer to the flavin
Cryptochrome mediated magnetic sensitivity in Arabidopsis occurs independently of light-induced electron transfer to the flavin
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DOI：
10.1039/c9pp00469f
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发表时间：
2020-03-01
影响因子：
3.1
通讯作者：
Ahmad, M.
中科院分区：
文献类型：
--
作者：
Hammad, M.;Albaqami, M.;Ahmad, M.
隐花色素是一种高度保守的蓝光吸收黄素蛋白，在植物发育过程中起光感受器的作用，在动物的生物钟中起作用。它们与许多生物体（包括植物、苍蝇和人类）对电磁场的感知有关。隐花色素感知磁场的机制被认为是通过所谓的自由基对机制发生的，由此在隐花色素激活过程中形成的自由基对的电子自旋可以被外部磁场操纵。然而，磁敏步骤和磁敏自由基对的身份仍然是一个有争议的问题。在这里，我们调查的500亩T（10倍地球的磁场），这是在一系列的迭代5分钟的蓝光/10分钟的暗脉冲的过程中施加的静磁场的效果。在相同的脉冲光条件下，隐花色素的反应，增强了磁场，即使曝光是专门提供在10分钟的黑暗间隔。然而，当磁刺激是专门在5分钟的光间隔，没有磁敏感性可以检测到。这一结果排除了隐花色素光循环过程中电子向黄素的正向转移过程中可能发生磁场敏感性的可能性。相比之下，隐花黄素再氧化过程中自由基对的形成将独立于光而发生，并在光照停止后持续数分钟。因此，我们的研究结果提供的证据表明，磁敏感的反应是encountered与暗态过程后隐花色素光还原步骤。
Cryptochromes are highly conserved blue light-absorbing flavoproteins which function as photoreceptors during plant development and in the entrainment of the circadian clock in animals. They have been linked to perception of electromagnetic fields in many organisms including plants, flies, and humans. The mechanism of magnetic field perception by cryptochromes is suggested to occur by the so-called radical pair mechanism, whereby the electron spins of radical pairs formed in the course of cryptochrome activation can be manipulated by external magnetic fields. However, the identity of the magnetosensitive step and of the magnetically sensitive radical pairs remains a matter of debate. Here we investigate the effect of a static magnetic field of 500 mu T (10x earth's magnetic field) which was applied in the course of a series of iterated 5 min blue light/10 min dark pulses. Under the identical pulsed light conditions, cryptochrome responses were enhanced by a magnetic field even when exposure was provided exclusively in the 10 min dark intervals. However, when the magnetic stimulus was given exclusively during the 5 min light interval, no magnetic sensitivity could be detected. This result eliminates the possibility that magnetic field sensitivity could occur during forward electron transfer to the flavin in the course of the cryptochrome photocycle. By contrast, radical pair formation during cryptochrome flavin reoxidation would occur independently of light, and continue for minutes after the cessation of illumination. Our results therefore provide evidence that a magnetically sensitive reaction is entwined with dark-state processes following the cryptochrome photoreduction step.