EAGER: Cell to cell communication in marine phytoplankton: population density dependent control of cellular processes

最近的发现表明，细胞间的交流从物种内延伸到跨王国水平，并在种群范围内的生物事件中发挥关键作用，如形态、代谢状态和种群结构的变化。群体感知(Quorum Sensing，QS)是一种通信过程，它允许单个小区协同工作，作为一个分散的网络。在原核生物和最近的真菌中的研究表明，QS调节关键生物学过程的时间，如菌落形成、孢子形成、形态变化、致病性和有性繁殖。在海洋环境中，QS已经在细菌中被证明，然而，对于浮游植物种群来说，这种相互合作的水平还没有被考虑。鉴于关于细胞-细胞交流的重要作用的新文献的出现，现在是时候重新考虑我们如何看待海洋浮游植物了。因此，远洋浮游植物细胞-细胞相互作用的研究主要集中在与其他物种竞争的化学信号(如化感作用)、捕食威慑和环境胁迫的预警系统。有几条间接证据支持浮游植物的QS，如细胞分裂的时间、密度依赖的化感作用和细胞程序性死亡。然而，据我们所知，还没有直接的实验来确定浮游植物是否可以在合作的联合体中发挥作用。他们是否有一种法定人数感应类型的通信来调节物种内的过程以及调节物种间的相互作用？循环浮游植物群落的建立是因为这些物种能够与每个成员进行交流，发挥特定的作用来维持种群吗？这些都是很难解决的问题，但对我们对浮游植物生态学的理解具有深远的影响。这个项目将通过研究特定生物事件的自我诱导过程(QS的基本租户)来测试浮游植物是否有QS系统。PIS将通过使用浮游植物生态和生理测量以及最先进的生物信息学和基因组学工具检查两个特定区域来测试这一点：i.根据与其他生物的QS相关基因的同源性，在现有的基因组和基因表达数据库中广泛搜索候选浮游植物QS相关基因。PI将进行详细的分析，以最终将这些QS调控通路的同源基因以及少数已知的QS化合物的生物合成途径和转录/翻译调节因子映射到浮游植物基因组上。这些结果将作为浮游植物细胞间通讯的比较基因组学研究的一部分，任何候选基因在QS中的可能作用将通过以下详细的实验进行测试(2).使用实验方法在硅藻物种中建立细胞过程的自动诱导。PIS将专注于利用两个模式硅藻物种--三角褐指藻和假海链藻的无菌培养自动诱导生长、细胞形态、化感作用和生物膜形成。智力优势：一个类似QS的交流系统的建立将为我们对浮游植物生态的看法带来一个新的视角，超越我们目前自下而上和自上而下控制或竞争相互作用的范式。这项研究的结果也将影响我们对控制浮游植物种群多样性的因素的看法，因为我们现在必须考虑物种间沟通的作用。通过一项迫切的提案提供资金，将为探索性、高风险研究提供支持，以获得最低限度的数据集，作为浮游植物QS概念的证据。广泛影响：PIs将与当地一所高中建立合作关系。他们试图通过教高中生从系统的角度审视生物现象来纠正生物学教学和实践中的不匹配。这将为他们在信息时代潜在的科学职业做好更好的准备，同时培养他们对当地海洋生态系统的好奇心。

Recent discoveries have shown that cell-cell communication extends from the intra-species to the inter-kingdom level and play pivotal roles in population-wide biological events such as changes in morphology, metabolic state and population structure. Quorum sensing (QS) is a communication process that allows single cells to cooperatively function as a decentralized network. Studies in prokaryotes and, more recently, fungi have demonstrated that QS regulates the timing of key biological processes such as colony formation, sporulation, morphological changes, pathogenicity and sexual reproduction. In the marine environment, QS has been demonstrated in bacteria however, this level of mutual cooperation has not been considered for phytoplankton populations. In view of the emerging literature on the critical role of cell-cell communication, it is timely to reconsider how we regard marine phytoplankton.Thus far marine phytoplankton cell-cell interaction studies have primarily focused on chemical signals for competition against other species (e.g. allelopathy), predation deterrence and warning systems for environmental stress. There are several lines of circumstantial evidence to support QS in phytoplankton such as the timing of cell division, density dependent allelopathy and programmed cell death. However, to our knowledge there has been no direct experimentation to determine if phytoplankton can function in a cooperative consortium. Do they have a quorum sensing- type of communication to regulate intra-species processes as well as modulates inter-species interactions? Are recurrent phytoplankton communities established because these species are able to communicate with each member serving a specific role to maintain the population? These are difficult questions to address but have far reaching implications in our understanding of phytoplankton ecology.This project will test whether phytoplankton have a QS system by examining the process of autoinduction (a basic tenant for QS) for specific biological events. The PIs will test this by examining two specific areas using phytoplankton ecological and physiological measurements coupled with state of the art bio-informatic and genomic tools:I. Perform an extensive search for candidate phytoplankton QS-related genes in existing genomic and gene expression databases, based on homology with QS-related genes from other organisms. The PIs will conduct a detailed analysis to definitively map homologs of these QS regulatory pathways in their entirety as well as the few known biosynthetic pathways of QS compounds and transcriptional/translational regulators onto phytoplankton genomes. The results will be included as part of a comparative genomics study on cell-to-cell communication in phytoplankton, and the possible role of any candidate genes in QS will be tested by the experiments detailed below (2).II. Establish autoinduction of cellular processes in a diatom species using an experimental approach. The PIs will focus on the autoinduction of growth, cell morphology, allelopathy and biofilm formation using axenic cultures using two model diatom species, Phaeodactylum tricornutum Bohlin and Thalassiosira pseudonana.Intellectual Merit: The establishment of a QS-like communication system will bring in a new perspective to our views on phytoplankton ecology beyond our current paradigm of bottom-up and top-down controls or competitive interactions. Results from this study will also influence our views on the factors controlling phytoplankton population diversity, as we will now have to consider the role of inter-species communication. Funding through an EAGER proposal will provide support for exploratory, high-risk research to obtain a minimum set of data as proof of concept of QS in phytoplankton.Broader Impacts: The PIs will establish a collaboration with a local high school. They seek to remedy the mismatch in the way biology is taught and practiced by teaching high-school students to examine biological phenomena from a systems perspective. This will better prepare them for potential science careers in the information era while fostering their curiosity about their local marine ecosystem.