Collaborative Research: Investigations of the Plant Photoreceptor Kinase Family of Photoreceptors

植物光感受器在植物整个发育过程中调节广泛的反应范围，从种子萌发到营养生长的所有阶段，再到开花和衰老。这些光感受器包括光敏色素、隐色素和趋光素。另外三个参与植物节律调控的蛋白质，FKF1，LKP2和ZTL，可能形成了植物光受体的第四个家族。向光性激素(Phot1和Pho2)介导植物的几种蓝光反应，包括：向光性、叶绿体重新定位、气孔开放、叶片展开和黄化幼苗生长的快速抑制。它们包含两个光敏结构域(LOV1和LOV2)，每个结构域都非共价结合一个FMN发色团和一个激酶域。光刺激LOV结构域可激活该激酶，并使其自动磷酸化。拟南芥的趋光蛋白LOV结构域和更复杂的结构可以在转基因植物和异源系统中表达。这些构建体是光活性的，但它们的光化学可以被位点特异性突变干扰或选择性失活。本项目的重点是包括生色团结合域和全长蛋白在内的结构的生化和生物物理特征，以及它们在植物中补充功能的能力。这些研究将探索光激活的机制，包括最初的光化学和随后的分子内信号传播事件。这项研究将涉及使用时间分辨光学和振动光谱、标准和时间分辨荧光光谱和圆二色谱、时间分辨偏振光光谱以及分子结构变化的顺磁和光谱探针。对趋光素的研究发现了一个生色团模块，LOV结构域起到光驱动分子开关的作用。这些LOV结构域与PAS结构域超家族密切相关，这些超家族结构域存在于各种生物体的蛋白质中。这些研究应该为理解它们的功能提供一个新的维度。研究和教育的整合是这个项目的一个重要组成部分。这种融合包括对博士后研究员和研究生的培训，以及对本科生的指导，包括那些来自代表性不足群体的学生。将继续向高中生和教师进行宣传。

Plant photoreceptors mediate a broad spectrum of responses throughout plant development, from seed germination through all phases of vegetative growth to flowering and senescence. These photoreceptors include phytochromes, cryptochromes, and phototropins. Three additional proteins, FKF1, LKP2 and ZTL, involved in regulation of plant rhythms, likely form a fourth family of plant photoreceptors. The Phototropins (phot1 and phot2) mediate several blue light responses in plants including: phototropism, chloroplast relocation, stomatal opening, leaf expansion and the rapid inhibition of growth of etiolated seedlings. They contain two light-sensing domains (LOV1 and LOV2), each non-covalently binding an FMN chromophore, and a kinase domain. Light stimulation of the LOV domains leads to activation the kinase, and autophosphorylation. Arabidopsis phototropin LOV domains and more complex constructs can be expressed in transgenic plants and heterologous systems. These constructs are photoactive, but their photochemistry can be perturbed or selectively inactivated with site-specific mutations. This project focuses on the biochemical and biophysical characterization of constructs including the chromophore-binding domains and the full-length protein, and their ability to complement function in plants. These studies will probe the mechanism of light activation including the initial photochemistry and subsequent intramolecular signal-propagation events. This research will involve the use of time-resolved optical and vibrational spectroscopy, standard and time-resolved fluorescence and circular dichroism spectroscopy, time-resolved polarized light spectroscopy, and paramagnetic and spectroscopic probes of molecular structural changes. Studies on the phototropins have uncovered a chromophore module, the LOV domain that functions as a light-driven molecular switch. These LOV domains are closely related to the superfamily of PAS domains found in proteins in a diverse range of organisms. These studies should provide a new dimension in the understanding of their functions.Integration of research and education is an essential component of this project. This integration involves training of post-doctoral fellows and graduate students and mentoring of undergraduate students, including those from underrepresented groups. Outreach to high school students and teachers will continue.