Regulatory and Functional Characterization of Modular Photoprotective Proteins in the Context of Cyanobacterial Ecology and Evolution

光合生物在光合作用过程中将光能转化为化学能。然而，吸收超过可用于光合作用的光可导致光诱导的损害。因此，光保护机制已经在光合生物中进化，以处理过度的光吸收或压力条件，包括波动的光。蓝藻所使用的光保护机制最近才开始被表征。蓝藻光保护中的一个关键因素是橙子类胡萝卜素蛋白（OCP），它与荧光恢复蛋白（FRP）一起将多余的光能转化为热量，以保护光合反应中心免受光损伤，从而保持光合效率和生产力。拟议中的工作将有助于更好地了解这些蛋白质的变体的范围内存在于生态上不同的蓝藻。除了以不同的方法培训学生和博士后科学家外，该研究的更广泛影响还包括了解蓝藻用于保护自己免受过度光吸收和相关光诱导损伤的机制。这些知识将加强努力，以提高光捕获的效率，减少生物能源或蓝藻生产菌株的光损伤。该项目还包括为来自科学领域代表性不足的群体的本科生提供实践研究方面的结构化指导，并参加当地科学博物馆针对中小学生的年度微生物学日。与植物相反，蓝藻的光保护机制最近才开始被表征。其中最普遍的是OCP/FRP（橙子类胡萝卜素蛋白/荧光恢复蛋白）系统，其通过耗散由光捕获天线（藻胆体或PBS）捕获的过量能量来响应强光。 OCP是结合单个类胡萝卜素分子的可溶性35 kDa蛋白质。 它是唯一已知的光活性蛋白质，使用类胡萝卜素作为其唯一的发色团。蓝绿光的吸收导致OCP从暗稳定的橙子形式OCPO转化为光激活的红色形式OCPR。 OCPR通过与PBS结合直接参与光保护。 从能量耗散状态的恢复由FRP催化。 在结构上，OCP由两个域组成，一个作为传感器/调节域，而另一个直接在能量耗散中起作用。 我们已经确定了一个家庭的旁系同源基因编码的不同领域的Fremyella diplosiphon和假设，他们反映了OCP的演变，他们提供的灵活性，在动态环境条件下调整光保护Fremyella。 将结合生物信息学来测试这些假设，在体内的方法在弗氏杆菌和体外分析的分离的蛋白质。 除了以不同的方法培训学生和博士后科学家外，该研究的更广泛影响还包括深入了解可能在蓝藻生物工程中有用的光保护机制的灵活性。

Photosynthetic organisms convert light energy to chemical energy in the process of photosynthesis. However, absorption of light in excess of that which can be used for photosynthesis can lead to light-induced damage. Thus, photoprotective mechanisms have evolved in photosynthetic organisms to deal with excess light absorption or stressful conditions, including fluctuating light. Photoprotective mechanisms used by cyanobacteria have only recently begun to be characterized. A key factor involved in cyanobacterial photoprotection is the Orange Carotenoid Protein (OCP) that works together with the Fluorescence Recovery Protein (FRP) to convert excess light energy to heat to protect the photosynthetic reaction centers from photodamage, thereby maintaining photosynthetic efficiency and productivity. The proposed work will contribute to a greater understanding of the range of variants of these proteins that are present in ecologically distinct cyanobacteria. In addition to training students and postdoctoral scientists in diverse methods, broader impacts of the research include understanding the mechanisms used by cyanobacteria to protect themselves from excess light absorption and associated light-induced damage. Such knowledge will enhance efforts to increase the efficiency of light capture and reduce photodamage in bioenergy or production strains of cyanobacteria. The project also includes structured mentoring in hands-on research for undergraduates from groups underrepresented in the sciences and participation in an annual Microbiology Day at a local science museum targeting primary and middle school students. In contrast to those of plants, the photoprotective mechanisms of cyanobacteria have only recently begun to be characterized. One of the most prevalent, the OCP/FRP (Orange Carotenoid Protein/Fluorescence Recovery Protein) system responds to high light by dissipating excess energy captured by the light harvesting antenna (phycobilisome or PBS). The OCP is a soluble, 35 kDa protein that binds a single carotenoid molecule. It is the only known photoactive protein that uses a carotenoid as its sole chromophore. The absorption of blue-green light causes the OCP to convert from a dark stable orange form, OCPO, to a light-activated red form, OCPR. OCPR directly participates in photoprotection by binding to the PBS. Recovery from the energy-dissipative state is catalyzed by the FRP. Structurally, the OCP consists of two domains, one serving as a sensor/regulatory domain whereas the other functions directly in energy dissipation. We have identified a family of paralogous genes encoding the separate domains in Fremyella diplosiphon and hypothesize that they reflect the evolution of the OCP and that they provide flexibility in tuning photoprotection in Fremyella under dynamic environmental conditions. A combination of in vivo approaches in Fremyella and in vitro analysis of the isolated proteins will be used in conjunction with bioinformatics to test these hypotheses. In addition to training students and postdoctoral scientists in diverse methods, broader impacts of the research include an in-depth understanding of the flexibility of photoprotective mechanisms that may be useful in bioengineering of cyanobacteria.