Collaborative Research: Investigations of the plant and bacterial family of LOV-domain flavoproteins

智力优势：植物光感受器识别光信号，检测光的方向、光的强度、光的颜色和光的持续时间。它们利用这些信号来调节植物发育的几乎每一个阶段，从种子萌发到开花、果实发育和衰老。已知的植物光感受器有四组：能感知红光和近红外光的光敏色素，以及能感知蓝光和近紫外光的隐色素、趋光蛋白和一个由三种趋光蛋白相关的光感受器家族。趋光性是指引导植物向光源方向生长的光感受器（趋光性）；调整叶片角度，最大限度地捕获光合作用所需的光；调整进行光合作用的小细胞器（叶绿体）的位置，使其展开，并最大限度地减少自遮光，以便在昏暗的光线下最大限度地捕捉光线（或移动到最大限度地增加自遮光的位置，以避免光线过多造成的损害）；并诱导叶片表面的小气孔（称为气孔）打开，以促进光合作用所需的二氧化碳的吸收。促光素包含两个连续的氨基酸片段，它们在核黄素衍生物分子周围形成一个口袋，核黄素衍生物是一种负责吸收蓝光的黄色色素。这些片段被指定为LOV结构域，因为它们与感知光、氧或电压的结构域相似。在吸收蓝光后，光激活色素改变蛋白质的形状，启动导致最终生物反应的步骤-可能是向光性，叶片定位，叶绿体运动或气孔打开。这种吸收光的蛋白质口袋（LOV结构域）也存在于低等植物、许多不同种类的真菌和大量细菌的重要蛋白质中。布鲁氏菌是一种剧毒的动物病原体，研究表明，光吸收可使细菌的毒力增加十倍。这种反应是由含有lov结构域的蛋白介导的。目前的项目有两个重点：首先，继续研究LOV结构域的形状变化如何被传递成一个信号，诱发几种生物反应之一，使用生化技术识别在光激发下与含有LOV结构域的蛋白质相互作用的其他蛋白质。目的是确定从光吸收到响应的整个事件链。其次，利用生物物理和生化方法研究根瘤菌的光响应，根瘤菌与豆科植物一起对固氮至关重要。与布鲁氏菌病病原体一样，根瘤菌具有一种含有lov结构域的信号蛋白，该信号蛋白影响其暴露于光下的行为。该研究将利用生物物理和生物化学方法来追踪从光吸收到细菌行为改变的步骤，研究以前未描述的光在这种农业上重要细菌中的作用。该项目旨在阐明一个小的含有色素的蛋白质口袋一方面可以提高细菌的发病机制，另一方面在蓝光激活下叶片气孔的打开。更广泛的影响：将研究和教育结合起来，培养博士后和研究生，指导本科生（UCSC需要一篇研究论文）和暑期实习生，包括本科生和高中生，这是该项目的重要组成部分。许多学生是由少数族裔项目赞助的- MARC（少数族裔获得研究职业），MBRS （NIH少数族裔生物医学研究支持），在Access项目下工作的暑期社区大学生（Access：通往未来的学士学位桥梁，NIH桥梁项目的一部分）和CAMP（加州少数族裔参与联盟）。温斯洛·布里格斯（Winslow Briggs）在当地的州立公园向公众进行了部分基于他的研究的解释性演讲。面向高中生、教师和大学本科生的暑期实习将继续开展。最后，预计这项研究本身最终将对农业和健康问题产生影响。

Intellectual Merit: Plant photoreceptors recognize light signals that detect light direction, light intensity, light color, and light duration. They use these signals to regulate almost every phase of plant development from seed germination through flowering, fruit development, and senescence. There are four known groups of plant photoreceptors: the phytochromes that can sense red and near-infrared light, and the cryptochromes, phototropins, and a family of three photoreceptor relatives of the phototropins, all of which can sense both blue and near-ultraviolet light. The phototropins are the photoreceptors that direct plant growth toward a light source (phototropism); adjust the leaf angle to maximize light capture for photosynthesis; adjust the positions of the small organelles that carry out photosynthesis (chloroplasts) to spread them out and minimize self-shading in order to maximize light capture in dim light (or to move into positions maximizing self-shading to avoid damage caused by too much light); and to induce the opening of small pores in the leaf surface (called stomata) to facilitate the uptake of carbon dioxide needed for photosynthesis. The phototropins contain two sequential segments of amino acids that form a pocket surrounding a molecule of a riboflavin derivative, a yellow pigment that is responsible for absorbing blue light. The segments are designated LOV domains for their similarity to domains that sense light, oxygen, or voltage. On absorption of blue light, the light-activated pigment alters the shape of the protein to initiate the steps leading to the eventual biological response - be it phototropism, leaf positioning, chloroplast movement, or stomatal opening. This light-absorbing protein pocket (the LOV domain) is also found in important proteins in lower plants, many different kinds of fungi, and a large number of bacteria. In the bacterium Brucella, a virulent animal pathogen, light absorption has been shown to induce a ten-fold increase in bacterial virulence. This response is mediated by a LOV-domain-containing protein. The present project has two foci: First, to continue to investigate how the change in shape of the LOV domain is transmitted into a signal that induces one of the several biological responses, using biochemical techniques to identify other proteins which interact with the LOV-domain-containing proteins on light excitation. The objective is to determine the complete chain of events from light absorption to response. Second, it will investigate, using biophysical and biochemical methods, the light responses of the bacterium Rhizobium, essential together with legumes for nitrogen fixation. Like the brucellosis pathogen, Rhizobium has a LOV-domain-containing signaling protein that affects its behavior on exposure to light. The research will investigate the previously un-described role of light in this agriculturally important bacterium using biophysical and biochemical methods to trace the steps from light absorption to alteration in the bacterial behavior. The project aims to elucidate the common mechanism by which a single small pigment-containing protein pocket can elevate pathogenesis in a bacterium on the one hand, and the opening of stomatal pores on a leaf on the other when activated by blue light. Broader Impact: Integration of research and education in the training of post-doctoral fellows and graduate students and mentoring of undergraduate students (a research thesis is required at UCSC) and summer interns, both undergraduate and high school is an essential component of this project. Many of the students are sponsored by minority programs - MARC (Minority Access to Research Careers), MBRS (NIH Minority Biomedical Research Support), Summer Community College Students working under the ACCESS program (ACCESS: Baccalaureate Bridges to the future, part of NIH Bridges program), and CAMP (California Alliance for Minority Participation). Winslow Briggs gives interpretive talks to the public at a local state park based partially on his research. Outreach to high-school students, teachers and college undergraduates will continue in the form of summer internships. Finally, it is anticipated that the research itself will ultimately impact both agriculture and health issues.