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

珊瑚礁是全球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结构基础的动物，它们的细胞内含有微小的藻类。这种互惠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。虽然大量的注意力集中在珊瑚的环境威胁以及珊瑚如何以及是否能够在气候变化中生存，但对支撑珊瑚-藻类共生的微尺度细胞和分子机制的理解仍然是部分的。深入了解这种共生关系的调节将为研究海洋变暖、酸化和其他人为压力因素对珊瑚健康的影响提供更坚实的基础。该项目将汇集一位珊瑚生物学家、一位化学家和一位癌细胞生物学家，研究共生伙伴发起和维持共生关系所参与的复杂的分子和细胞对话。该项目还将研究在珊瑚白化现象期间，这些对话是如何出错并导致共生功能障碍和崩溃的。珊瑚白化是对温度升高的应激反应，导致珊瑚死亡和珊瑚礁退化。除了实地研究珊瑚外，本计划亦会研究海葵。海葵是珊瑚的优良代表，其中许多已濒临灭绝，难以在实验室环境中培育。这个项目将有助于培训科学家，并使学龄儿童了解珊瑚礁和共生科学。许多刺胞动物，包括珊瑚和海葵，与光合鞭毛藻（Symbiodinium spp.）共生，共同构成珊瑚礁生态系统的营养和结构基础。尽管珊瑚对珊瑚礁很重要，而且在气候急剧变化的时代，珊瑚礁的健康状况受到威胁，但人们对这种伙伴关系开始、建立和破裂的基本细胞和分子机制只了解了一部分。本项目将研究刺胞-鞭毛藻共生开始和破裂过程中的伙伴间信号传导和宿主细胞免疫反应。实验将在两个模型系统中进行，海葵Aiptasia sp.-Symbiodinium B1和珊瑚真菌scuaria - symbiodinium C1f的幼虫。该团队提出了以下具体目标：目标1：通过聚糖谱分析和藻类的糖操纵以及宿主受体下拉方法来表征宿主和入侵共生菌之间的聚糖识别。目的2：通过分析不同共生体类型和其他颗粒对宿主的吞噬谱、吞噬体标记物、NF-kB激活和信号传导鞘氨醇变阻器，比较共生菌对宿主吞噬和细胞内信号传导的结构动力学。目的3：通过测量高温胁迫后宿主组织中吞噬体成熟、NF-kB激活和鞘脂信号的变化，研究在高温胁迫下导致白化的伙伴关系中吞噬体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.