EAGER: Diatom Programmed Cell Death at Single-Cell Resolution

硅藻是遍布地球仪阳光照射下的海洋和湖泊中重要的初级生产者。它们是春季浮游植物大量繁殖的关键因素，而浮游植物又反过来支持包括生产性渔业在内的食物网。此外，这些光合作用硅藻细胞被称为捕获大量的碳，这些碳被出口到深处，因为水华死亡。在海洋系统中，这一过程有效地从大气中去除了数千年的碳。然而，导致碳固存的生物机制，即碳从大气层转移到深海，还没有得到很好的理解。随着硅藻种群达到水华周期的结束，单个细胞开始恶化并经历细胞死亡。硅藻种群的崩溃被认为是一个临界点（或临界点），可以通过了解种群的遗传活性来预测。本项目旨在阐明环境变化如何影响硅藻细胞死亡过程。对这些细胞过程的机械理解将阐明气候变化如何改变大气中的碳去除并影响海洋生产力。在这项研究中开发的知识和方法适用于所有生命领域的生物体。该项目更广泛的影响集中在高中教育和三维学习机会的新思路和新方法，以支持下一代科学标准（NGSS）。具体而言，研究人员正在与高中教育工作者和合作伙伴合作，通过教育模块教授系统方法，临界点和海洋环境中的碳封存概念，目标是通过确定单个细胞水平的承诺点（临界点）来确定活跃生长细胞向种群崩溃过渡期间硅藻种群的结构。模式系统是硅藻，海链藻，这是广泛和常见的水华形成物种。个体硅藻细胞的随机决策过程的特征在于通过细胞的物理和生物化学表征建立全基因组基因表达空间。该项目的实施重点是测量硅藻对包括严重压力在内的环境因素的表型反应。在细胞增殖向培养物崩溃过渡期间的转录组学分析包括批量（RNA-Seq）和单细胞（scRNA-Seq）高通量测序。使用系统生物学方法，从样本中获得的遗传信息被纳入预测模型，以识别在种群崩溃之前发生的遗传转变。系统方法可以检测转录组状态的变化，这些变化发生在细胞死亡过程中的临界点之前，从而预测硅藻对环境变化的反应。 这项工作为阐明硅藻细胞种群的机制途径开辟了新的前景。该奖项反映了NSF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。

Diatoms are important primary producers in sunlit oceans and lakes across the globe. They are key players in spring phytoplankton blooms, which in turn support food webs that include productive fisheries. In addition, these photosynthetic diatom cells are known to capture enormous amounts of carbon, which are exported to depth as blooms die off. In oceanic systems, this process effectively removes carbon from the atmosphere for thousands of years. However, the biological mechanisms that lead to carbon sequestration, the transfer of carbon from the atmosphere into the deep ocean, are not well understood. As diatom populations reach the end of the bloom cycle, individual cells start to deteriorate and undergo cell death. The collapse of diatom populations is regarded as a critical point (or tipping point), which can be predicted by understanding the genetic activity of the population. This project seeks to elucidate how environmental change influences diatom cell-death processes. A mechanistic understanding of these cellular processes will elucidate how climate change could alter carbon-removal from the atmosphere and affect ocean productivity. The knowledge and methods developed during this study are applicable across organisms from all domains of life. The broader impacts of this project are focused on high school education and new ideas and approaches for three-dimensional learning opportunities in support of Next Generation Science Standards (NGSS). Specifically, researchers are working with high school educators and partners to teach concepts of systems approaches, tipping points, and carbon sequestration in the marine environment through educational modules.The goal is to determine the structure of diatom populations during the transition of actively growing cells towards population collapse by identifying the point of commitment (tipping point) at the level of individual cells. The model system is the diatom, Thalassiosira pseudonana, which is widespread and a common bloom-forming species. The random decision process of individual diatom cells is being characterized by establishing a genome-wide gene expression space through the physical and biochemical characterization of the cells. Implementation of the project is focused on measuring the phenotypic responses in the diatom to environmental factors including severe stress. Transcriptomic analyses during the transition of cell proliferation towards culture collapse include bulk (RNA-Seq) and single-cell (scRNA-Seq) high-throughput sequencing. Using a systems biology approach, the genetic information obtained from the samples is incorporated into predictive models to identify genetic transitions that occur prior to population collapse. The systems approach can detect changes in transcriptomic state that precede a critical point in the cell death process leading to predictions of how diatoms respond to environmental change. This work opens new vistas for the elucidation of mechanistic pathways of diatom cell populations.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.