Function of and signaling by blue light photoreceptors in Rhodobacter sphaeroides

虽然光感受器已经在许多细菌物种中被发现，但它们的生物学功能和信号感知下游的信号大多是难以捉摸的。在过去的研究中，我们发现了一种新型的光感受器——球藻AppA蛋白的BLUF结构域。在高氧水平下，它参与了依赖蓝光的光合作用基因的抑制。最近，我们发现了隐色素样CryB蛋白和lov结构域蛋白结合黄素并进行光循环。我们可以证明CryB强烈影响光合作用基因的表达。因此，可以首次将明确的生物学功能赋予细菌隐色素。在本项目中，我们希望解开CryB到光合作用基因表达的信号链，表征CryB的黄素结合域，并阐明CryB的光循环与下游信号传导的关系。通过酵母双杂交筛选LOV蛋白的相互作用伙伴表明其参与胶囊合成的调节。我们将详细分析光在胶囊合成和LOV信号传导中的作用。我们期望我们的结果将为细菌光感受器的生物学作用和光感知下游的信号传导机制提供新的见解。

Although photoreceptors have now been identified in many bacterial species, their biological function and signaling downstream from signal perception are mostly elusive. In the past we identified the BLUF domain of the AppA protein from R. sphaeroides as a new type of photoreceptor. It is involved in a blue light-dependent repression of photosynthesis genes at elevated oxygen levels. Recently we revealed that the cryptochrome-like CryB protein and the LOV-domain protein of R. sphaeroides bind flavins and undergo a photocycle. We could show that CryB strongly affects the expression of photosynthesis genes. Thus a clear biological function can be assigned to a bacterial cryptochrome for the first time. In the proposed project we want to unravel the signal chain from CryB to the expression of photosynthesis genes, to characterize the flavin binding domain of CryB, and to elucidate, how the photocycle of CryB relates to downstream signaling. A search for interaction partners of the LOV protein by a yeast two-hybrid screening suggests its involvement in the regulation of capsule synthesis. The role of light in capsule synthesis and signaling by LOV will be analysed in detail. We expect that our results will provide new insights into the biological role of bacterial photoreceptors and the mechanisms of signaling downstream of light perception.