ATP boosts lit state formation and activity of Arabidopsis cryptochrome2

First author: Maike Eckel; Affiliations: Philipps‐Universität Marburg (马尔堡菲利普大学): Marburg, Germany

Corresponding author: Alfred Batschauer

Cryptochrome (cry; 隐花色素) blue light photoreceptors (蓝光光受体) have important roles in the regulation of plant development. Their photocycle includes redox (氧化还原) changes of their FAD chromophore (生色团), which is fully oxidized in the dark state and semi‐r educed in the signalling‐active lit state. The two Arabidopsis thaliana cryptochromes cry1 and cry2 and the plant‐ ype cryptochrome CPH1 from Chlamydomonas rheinhardtii (衣藻) bind ATP and other nucleotides. ATP binding affects the photocycle of these photoreceptors and causes structural alterations. However, the exact regions that undergo structural changes have not been defined, and most importantly, it is not known whether ATP binding affects the biological activity of these photoreceptors in planta. Here we present studies on the effect of ATP on Arabidopsis cry2. Recombinant cry2 protein showed a high affinity for ATP (KD of 1.09 ± 0.48 μM). Binding of ATP and other adenines (腺嘌呤) promoted photoreduction (光化学还原) of the FAD chromophore in vitro and caused structural changes, particularly in α‐helix 21, which links the photosensory domain (感光结构域) with the C‐ erminal extension. The constructed cry2Y399A mutant was unable to bind ATP and did not show enhancement of photoreduction by ATP. When this mutant gene was expressed in Arabidopsis null cry2 mutant plants, it retained some biological activity, which was, however, lower than that of the wild‐ ype. Our results indicate that binding of ATP to cry2 and most likely to other plant‐ ype cryptochromes is not essential but boosts the formation of the signalling state and the biological activity.

隐花色素cry蓝光光受体对于植物发育调控具有非常重要的作用。这些光受体的光循环包括了FAD生色团的氧化还原改变，在黑暗条件下完全被氧化，而在激活的光条件下被部分还原。两个拟南芥隐花色素cry1和cry2以及来自衣藻的植物隐花色素CPH1能够结合ATP和其它核苷酸。ATP结合到隐花色素上能够影响光受体的光循环，并导致结构变化。然而，目前仍未知道哪些区域会发生结构变化，并且ATP结合是否会影响这些光受体在植物体内的生物活性。本文研究了ATP对于拟南芥cry2的影响。重组的cry2蛋白对于ATP具有非常高的亲和性。结合ATP和其它的一些腺嘌呤会促进离体条件下FAD生色团的光化学还原，并导致结构变化，尤其是连接感光结构域和C末端区域的α‐螺旋21。人工构建的cry2Y399A突变体不能结合ATP，并且ATP不能增强光化学还原。该突变基因在cry2缺失纯合突变体的拟南芥中表达仍能保留一些生物活性，但要比野生型的活性要低。本文的研究显示ATP结合到cry2和其它的一些植物隐花色素上能够增强激活态的形成和光受体的生物活性。

通讯：Alfred Batschauer (https://www.uni-marburg.de/fb17/fachgebiete/pflanzenphysio/pflanzphysII/index_html)

研究方向：植物和真菌中的光受体及DNA修复酶。

doi: https://doi.org/10.1111/tpj.14039

Journal: the plant journal

First Published: 25 July, 2018

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