Sullivan Stuart, Petersen Jan, Blackwood Lisa, Papanatsiou Maria, Christie John M
Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Bower Building, Glasgow, G12 8QQ, UK.
New Phytol. 2016 Jan;209(2):612-23. doi: 10.1111/nph.13640. Epub 2015 Sep 28.
Phototropins (phots) regulate a range of adaptive processes in plants that serve to optimize photosynthetic efficiency and promote growth. Light sensing by Arabidopsis thaliana phots is predominantly mediated by the Light, Oxygen and Voltage sensing 2 (LOV2) flavin-binding motif located within the N-terminus of the photoreceptor. Here we characterize the photochemical and biochemical properties of phot from the marine picoalga Ostreococcus tauri phototropin (Otphot) and examine its ability to replace phot-mediated function in Arabidopsis. Photochemical properties of Otphot rely on both LOV1 and LOV2. Yet, biochemical analysis indicates that light-dependent receptor autophosphorylation is primarily dependent on LOV2. As found for Arabidopsis phots, Otphot associates with the plasma membrane and partially internalizes, albeit to a limited extent, in response to blue-light irradiation. Otphot is able to elicit a number of phot-regulated processes in Arabidopsis, including petiole positioning, leaf expansion, stomatal opening and chloroplast accumulation movement. However, Otphot is unable to restore phototropism and chloroplast avoidance movement. Consistent with its lack of phototropic function in Arabidopsis, Otphot does not associate with or trigger dephosphorylation of the phototropic signalling component Non-Phototropic Hypocotyl 3 (NPH3). Taken together, these findings indicate that the mechanism of action of plant and evolutionarily distant algal phots is less well conserved than previously thought.
向光素（phots）调控植物中的一系列适应性过程，这些过程有助于优化光合效率并促进生长。拟南芥向光素的光感知主要由位于光感受器N端的光、氧和电压感应2（LOV2）黄素结合基序介导。在这里，我们表征了来自海洋微微型藻类莱茵衣藻向光素（Otphot）的光化学和生化特性，并研究了其在拟南芥中替代向光素介导功能的能力。Otphot的光化学特性依赖于LOV1和LOV2。然而，生化分析表明，光依赖性受体自磷酸化主要依赖于LOV2。正如在拟南芥向光素中所发现的，Otphot与质膜结合，并在蓝光照射下部分内化，尽管程度有限。Otphot能够在拟南芥中引发许多光调节过程，包括叶柄定位、叶片扩展、气孔开放和叶绿体积累运动。然而，Otphot无法恢复向光性和叶绿体回避运动。与其在拟南芥中缺乏向光性功能一致，Otphot不与向光信号成分非向光性下胚轴3（NPH3）结合或触发其去磷酸化。综上所述，这些发现表明植物和进化上距离较远的藻类向光素的作用机制不如以前认为的那样保守。
