RUI: Evaluating how cnidarian hosts and algal endosymbionts coordinate cell divisions to maintain healthy symbiosis

由于海水温度升高导致珊瑚白化，并驱逐了它们赖以生存的共生藻类，负责建造热带珊瑚礁的珊瑚正在以惊人的速度消失。没有这些共生体，珊瑚就无法从阳光中获取能量，因此，在热带营养贫乏的水域中，珊瑚很难茁壮成长，甚至无法生存。为了解决对珊瑚礁的威胁，有必要了解支撑漂白过程的细胞事件。事实上，我们对健康珊瑚和共生体如何协调细胞分裂知之甚少，尽管藻类存在于单个珊瑚细胞中。事实上，珊瑚和藻类细胞分裂的分离与白化有关。本提案的目的是确定藻细胞周期失调在白化中所起的作用，并评估与共生细胞分裂调节有关的两种机制。了解这一点可以为减轻珊瑚白化的策略提供信息。在伍福德学院，该提案将资助9个本科生研究项目，生成公开可用的测序数据，这些数据将改变生物信息学教学，并为本科生生物学课程的各个层次的课程研究提供物质支持。参加课程研究的学生与参加传统研究项目的学生受益相似；然而，由于这些课程是在常规学期进行的，因此这些课程缺乏障碍，无法阻止来自代表性不足群体的学生参与。总的来说，拟议的活动将提高南卡罗来纳州经济最多样化大学50多名本科生的教育成果。该项目的目标将通过完成以下三个具体目标来实现：(1)测量热应激与共生生物增殖增加之间的联系；(2)通过比较培养共生体与宿主共生体的基因表达和膜脂组成，评估磷酸盐限制作为宿主调节藻类增殖的机制；(3)从药理学和遗传学上改变共生体与其宿主分离的细胞内腔室的pH值，并测量pH值对藻类细胞分裂的影响。核心假设是热应激导致宿主和共生体细胞周期的分离，这是通过磷酸盐交换和藻类微环境的pH来协调的。这项工作对该领域很重要，因为要解决应力引起的白化问题，必须揭示维持健康共生的机制。事实上，如果决定耐热性的细胞特征被阐明，就更容易预测哪些珊瑚最容易受到气候变化的影响，并将保护工作集中在这些物种上。同样，某些种类的藻类共生体对热引起的白化具有抗性。一种解释是，耐热物种分裂速度较慢，这使得它们在高温下不太可能过度繁殖，从而给宿主造成负担。我们的工作将提供这方面的见解，并可能使确定最佳物种接种到用于珊瑚礁恢复的幼珊瑚中变得更容易。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The corals responsible for building tropical reefs are disappearing at an alarming rate as elevated sea temperatures cause them to bleach and expel the algal symbionts they rely on. Without these symbionts, corals are unable to harvest energy from sunlight and, therefore, struggle to thrive or even survive in the nutrient-poor waters of the tropics. To devise solutions to address the threat to coral reefs, it is necessary to understand the cellular events underpinning the bleaching process. Indeed, little is known about how healthy corals and symbionts coordinate cell divisions even though the algae reside within individual coral cells. In fact, uncoupling of coral and algal cell divisions has been implicated in bleaching. The objectives for this proposal are to determine what role dysregulation of the algal cell cycle plays in bleaching and to assess two mechanisms implicated in regulation of symbiont cell division. Understanding this may inform strategies for mitigating coral bleaching. At Wofford College, this proposal will fund nine undergraduate research projects, generate publicly available sequencing data that will transform bioinformatics instruction, and provide material support for course-based undergraduate research at all levels of the undergraduate biology curriculum. Students who participate in course-based research benefit similarly to students who participate in traditional research programs; however, because they occur during the regular semester, these courses lack the barriers to access that prevent participation by students from underrepresented groups. Altogether, the proposed activities will enhance educational outcomes for more than 50 undergraduates at South Carolina’s most economically diverse college.The objectives for this project will be accomplished by completing three specific aims: (1) to measure the link between heat stress and increased symbiont proliferation; (2) to assess phosphate limitation as a mechanism used by hosts to regulate algal proliferation by evaluating gene expression and membrane lipid composition in cultured symbionts compared to symbionts in hosts; and (3) to pharmacologically and genetically alter the pH of the intracellular compartment separating symbionts from their hosts and measure the effect of pH on algal cell division. The central hypothesis is that heat stress causes an uncoupling of host and symbiont cell cycles, which are coordinated through phosphate exchange and the pH of the algal microenvironment. This work is important for the field because to address stress-induced bleaching, the mechanisms responsible for maintaining healthy symbiosis must be uncovered. Indeed, if the cellular traits dictating thermotolerance are elucidated, it will be easier to predict which corals are most susceptible to climate change and to focus conservation efforts on those species. Likewise, certain species of algal symbiont are resistant to heat-induced bleaching. One proposed explanation is that thermotolerant species are slower to divide, making them less likely to over-proliferate at high temperatures and burden their hosts. Our work will provide insight into this and may make it easier to determine the best species to inoculate into juvenile corals being used for reef restoration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.