Glycan Recognition and the Role of Innate Immunity in Cnidarian-dinoflagellate Symbioses

珊瑚礁是世界范围内受到威胁的极其重要的生态系统。珊瑚是构成这些珊瑚礁的结构基础的动物，它们的细胞中含有微小的藻类。这种互惠互利的伙伴关系或共生关系为整个多样化的珊瑚礁生态系统提供了基础。虽然人们对珊瑚的环境威胁以及珊瑚如何以及是否能在气候变化中生存下来给予了极大的关注，但对支撑珊瑚-藻类共生的微观细胞和分子机制仍然只有部分了解。对这种共生规律的洞察将为研究海洋变暖、酸化和其他人为应激源对珊瑚健康的影响提供更坚实的基础。该项目将汇集一名珊瑚生物学家、一名化学家和一名癌细胞生物学家，研究共生伙伴为启动和维持共生而进行的复杂的分子和细胞对话。该项目还将研究这些对话是如何出错的，并在珊瑚白化现象期间导致共生功能障碍和崩溃，珊瑚白化是对导致珊瑚死亡和珊瑚礁退化的温度升高的压力反应。除了在野外研究珊瑚外，该项目还将研究海葵，这是珊瑚的极好替代品，许多珊瑚处于濒危状态，很难在实验室环境中培养。这个项目将有助于培训科学家，并让学龄儿童接触珊瑚礁和共生科学。许多珊瑚虫，包括珊瑚和海葵，与光合作用的甲藻(共生鞭毛虫)共生，它们共同构成珊瑚礁生态系统的营养和结构基础。在气候急剧变化的时代，尽管珊瑚对珊瑚礁很重要，珊瑚礁的健康状况受到威胁，但人们对伙伴关系启动、建立和破裂的基本细胞和分子机制只有部分了解。这个项目将研究在蛇行-甲藻共生体开始和破坏期间伙伴间的信号传递和宿主细胞免疫反应。实验将在两个模型系统中进行，即海葵Aiptasia sp.-Symbioddium B1和珊瑚Fungia skaaria-Symbioddium C1f的幼虫。该团队提出了以下具体目标：目标1：通过对藻类的糖链分析和糖糖操作，以及宿主受体下拉方法，表征宿主和入侵共生生物之间的葡聚糖识别。目的：通过分析不同共生菌类型和其他颗粒对宿主的吞噬特性、吞噬标志物、核因子-kB的激活以及信号转导鞘氨醇变阻器的影响，比较不同共生菌攻击宿主时吞噬细胞和细胞内信号的结构动力学。目的3：通过测量高温应激后宿主组织中吞噬体成熟、核因子-kB的激活和鞘磷脂信号的变化，来检测高温导致漂白的伙伴关系中吞噬动力学和细胞信号的中断和变化。

Coral reefs are profoundly important ecosystems that are threatened worldwide. Corals are animals that form the structural basis of these reefs, and contain microscopic algae inside their cells. This mutualistic partnership or symbiosis provides the foundation of the entire diverse coral reef ecosystem. While a great deal of attention has been focused on the environmental threats to corals and how and if corals will survive climate change, there remains only a partial understanding of the microscale cellular and molecular mechanisms that underpin the coral-algal symbiosis. Insight into regulation of this symbiosis will provide a stronger foundation for studies of the impact of ocean warming, acidification and other anthropogenic stressors on coral health. This project will bring together a coral biologist , a chemist, and a cancer cell biologist, to examine the intricate molecular and cellular conversations that the partners of the symbiosis engage in to initiate and maintain the symbiosis. The project will also examine how these conversations go awry and lead to symbiosis dysfunction and breakdown during the phenomenon of coral bleaching, a stress response to elevated temperature that results in coral death and reef degradation. In addition to studying corals in the field, this project will also study sea anemones which are an excellent proxy for corals, many of which are endangered and are difficult to culture in a laboratory setting. This project will contribute to the training of scientists and expose school-aged children to coral reef and symbiosis science.Many cnidarians, including corals and anemones, engage in symbioses with photosynthetic dinoflagellates (Symbiodinium spp.), and together they form the trophic and structural foundation of the coral reef ecosystem. Despite the importance of corals to coral reefs and the threatened state of coral reef health in an era of dramatic climate change, the basic cellular and molecular mechanisms underlying the initiation, establishment and breakdown of the partnership are only partially understood. This project will examine inter-partner signaling and host cell immune response during onset and breakdown of cnidarian-dinoflagellate symbioses. Experiments will be conducted in two model systems, the anemone Aiptasia sp.-Symbiodinium B1 and larvae of the coral Fungia scutaria-Symbiodinium C1f. The team proposes the following Specific Aims: Aim 1: Characterize glycan recognition between host and invading Symbiodinium by glycan profiling and glycome manipulation of the algae, and host receptor pull-down approaches. Aim 2: Compare structural dynamics of phagocytosis and intracellular signaling when hosts are challenged with Symbiodinium by analyzing phagocytic profiles, phagosomal markers, NF-kB activation and the signaling sphingosine rheostat in hosts challenged with different symbiont types and other particles. Aim 3: Examine disruptions and changes in phagosomal dynamics and cell signaling in partnerships subjected to elevated temperature that leads to bleaching by measuring changes in phagosomal maturation, activation of NF-kB and sphingolipid signaling in host tissues after an elevated temperature stress.