Department of Plant Physiology and Photobiology, Faculty of Biology, Philipps-University, 35032, Marburg, Germany.
Plant J. 2013 May;74(4):583-92. doi: 10.1111/tpj.12144. Epub 2013 Mar 15.
One crucial component in light signaling is the quantity of photoreceptor present in the active signaling state. The lifetime of the signaling state of a photoreceptor is limited because of thermal or otherwise back reversion of the chromophore to the ground state, and/or degradation of the photoreceptor in the light-activated state. It was previously shown that the lit state of plant cryptochromes contains flavin-neutral semiquinone, and that the half-lives of the lit state were in the range of 3-4 min in vitro. However, it was unknown how long-lived the signaling states of plant cryptochromes are in situ. Based on the loss of degradation of cry2 after prolonged dark incubation and loss of reversibility of photoactivated cry1 by a pulse of green light, we estimate the in vivo half-lives of the signaling states of cry1 and cry2 to be in the range of 5 and 16 min, respectively. Based on electron paramagnetic resonance measurements, the lifetime of the Arabidopsis cry1 lit state in insect cells was found to be ~6 min, and thus very similar to the lifetime of the signaling state in planta. Thus, the signaling state lifetimes of plant cryptochromes are not, or are only moderately, stabilized in planta.
在光信号中，一个关键的组成部分是处于活跃信号状态的光感受器的数量。由于热或其他原因，发色团恢复到基态，和/或光激活状态下的光感受器降解，光感受器的信号状态的寿命是有限的。先前已经表明，植物隐花色素的亮态含有黄素非中性半醌，并且亮态的半衰期在体外的 3-4 分钟范围内。然而，目前尚不清楚植物隐花色素的信号状态在体内能维持多长时间。基于长时间黑暗孵育后 cry2 降解的丧失和绿光脉冲对光激活的 cry1 可逆性的丧失，我们估计 cry1 和 cry2 的信号状态的体内半衰期分别在 5 到 16 分钟范围内。基于电子顺磁共振测量，发现拟南芥 cry1 亮态在昆虫细胞中的寿命约为 6 分钟，因此与体内信号状态的寿命非常相似。因此，植物隐花色素的信号状态寿命在体内没有或只有适度的稳定。
