Liao Xinyang, Liu Wei, Yang Hong-Quan, Jenkins Gareth I
Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow,, G12 8QQ, UK.
Shanghai Key Laboratory of Plant Molecular Sciences, College of Life Sciences, Shanghai Normal University, Shanghai, 200234, China.
New Phytol. 2020 Aug;227(3):857-866. doi: 10.1111/nph.16581. Epub 2020 May 13.
The photoreceptor UVR8 mediates numerous photomorphogenic responses of plants to UV-B wavelengths by regulating transcription. Studies with purified UVR8 and seedlings not previously exposed to UV-B have generated a model for UVR8 action in which dimeric UVR8 rapidly monomerises in response to UV-B exposure to initiate signalling. However, the mechanism of UVR8 action in UV-B-acclimated plants growing under photoperiodic conditions, where UVR8 exists in a dimer/monomer photo-equilibrium, is poorly understood. We examined UVR8 dimer/monomer status, gene expression responses, amounts of key UVR8 signalling proteins and their interactions with UVR8 in UV-B-acclimated Arabidopsis. We show that in UV-B-acclimated plants UVR8 can mediate a response to a 15-fold increase in UV-B without any increase in abundance of UVR8 monomer. Following transfer to elevated UV-B, monomers show increased interaction with both COP1, to initiate signalling and RUP2, to maintain the photo-equilibrium when the dimer/monomer cycling rate increases. Native RUP1 is present in low abundance compared with RUP2. We present a model for UVR8 action in UV-B-acclimated plants growing in photoperiodic conditions that incorporates dimer and monomer photoreception, dimer/monomer cycling, abundance of native COP1 and RUP proteins, and interactions of the monomer population with COP1, RUP2 and potentially other proteins.
光感受器UVR8通过调控转录介导植物对UV-B波长的多种光形态建成反应。对纯化的UVR8和之前未暴露于UV-B的幼苗进行的研究产生了一个UVR8作用模型，其中二聚体UVR8在暴露于UV-B时迅速单体化以启动信号传导。然而，在光周期条件下生长的UV-B适应植物中，UVR8以二聚体/单体光平衡状态存在，其作用机制尚不清楚。我们研究了UV-B适应的拟南芥中UVR8的二聚体/单体状态、基因表达反应、关键UVR8信号蛋白的量及其与UVR8的相互作用。我们发现，在UV-B适应的植物中，UVR8可以介导对UV-B增加15倍的反应，而UVR8单体的丰度没有任何增加。转移到升高的UV-B条件后，当二聚体/单体循环速率增加时，单体与COP1（启动信号传导）和RUP2（维持光平衡）的相互作用增强。与RUP2相比，天然RUP1的丰度较低。我们提出了一个在光周期条件下生长的UV-B适应植物中UVR8作用的模型，该模型纳入了二聚体和单体光感受、二聚体/单体循环、天然COP1和RUP蛋白的丰度，以及单体群体与COP1、RUP2和潜在其他蛋白的相互作用。
