Collaborative Research: Integration of metabolic cues and life cycle decisions in Chlamydomonas

单细胞生物体，如原生生物和细菌，生活在波动的环境中，那里的营养供应并不总是得到保证。为了应对这种“盛宴或饥荒”的不确定性，细胞进化了一些过程，允许它们在营养存在时通过生长和分裂做出适当的反应(增殖)，或者在饥饿时变得休眠并采取节能状态(静止)。该项目利用单细胞参考生物体--绿藻衣藻，来研究如何控制控制增殖和静止的分子开关，以及如何协调它们以确保它们不会相互干扰。像这样的微生物可以积累大量有价值的化合物，例如油，但只有在饥饿的情况下才能积累。预计，有关控制增殖状态和静止状态之间转换的分子开关的知识将有助于预测如何控制和设计这些状态。因此，新发现的关于这些分子开关的细节提供了潜在的工程策略，将高产量的有价值的化合物从饥饿反应中分离出来。来自这两个研究地点的学生和博士后研究员将合作确定静止和增殖的关键调控因子之间的相互作用并建立模型，这些调控因子在包括植物和动物在内的许多其他物种中都有对应的作用。方法的多样性和定量培训的组成部分为受训人员在工业或学术界的科学职业生涯做好了准备。该项目的长期目标是获得对营养和代谢信号如何整合到控制生命周期状态转变的连贯决策中的预测性理解。在单细胞绿藻Chlamydomonas reainhardtii中，已发现两种核蛋白复合体CHT7-C和Rb-C，它们控制着营养剥夺引起的细胞静止、细胞生长和细胞分裂承诺之间的转换。假设静止调节因子CHT7-C和细胞周期承诺调节因子RB-C形成一个连锁的转录网络，协调控制细胞对营养或代谢信号的生长和分裂反应。该项目的目标是：(1)鉴定纯化的CHT7-C和RB-C复合体，以确定它们在不同生命周期状态下的亚基组成和修饰；(2)识别CHT7-C和RB-C的靶基因，然后生成转录网络模型，以观察两个复合体在功能上偶联的共同节点；(3)将影响两个复合体的不同成分的突变结合到等基因系中，以获得合成表型，从而深入了解两个复合体在体内的功能和相互关系；以及(4)建立可测试的逻辑开关模型，并开发定量标记来测试和修订该模型。为研究静止和细胞增殖调节因子之间的相互作用而采取的合作方法旨在改变对建立和维持对代谢和营养信号的协调全球反应的网络的理解。

Single-celled organisms, such as protists and bacteria, inhabit fluctuating environments where nutrient availability isn't always guaranteed. To cope with this "feast or famine" uncertainty, cells have evolved processes that allow them to respond appropriately by growing and dividing when nutrients are present (proliferation), or by becoming dormant and adopting an energy-conserving state when starved (quiescence). This project utilizes a single-celled reference organism, the green alga Chlamydomonas, to investigate how molecular switches that govern proliferation and quiescence are controlled and how they are coordinated to ensure that they don't interfere with each other. Microorganisms like these can accumulate large quantities of valuable compounds, e.g. oils, but only when starved. It is anticipated that knowledge about the molecular switches governing transitions between the states of proliferation and quiescence will allow predictions about how these states can be controlled and engineered. Thus, newly discovered details about these molecular switches provide potential engineering strategies to uncouple high yields of valuable compounds from starvation responses. Students and postdoctoral fellows from the two research locations will collaborate to identify and model the interactions between key regulators of quiescence and proliferation that have counterparts in many other species including plants and animals. The diversity of approaches and quantitative training components prepare the trainees for science careers in industry or academia. The long term goal of this project is to gain a predictive understanding of how nutrient and metabolic cues are integrated into coherent decisions that control life cycle state transitions. In the unicellular green alga Chlamydomonas reinhardtii, two nuclear protein complexes, CHT7-C and RB-C, have been identified that govern the transitions between nutrient-deprivation induced quiescence, cell growth, and commitment to cell division. It is hypothesized that the quiescence regulator CHT7-C, and the cell cycle commitment regulator RB-C form an interlocking transcriptional network that coordinately controls cell growth and division responses to nutrient or metabolic cues. The objectives of this project are to: (1) characterize purified CHT7-C and RB-C complexes in order to define their subunit composition and modifications under different life cycle states; (2) Identify CHT7-C and RB-C target genes followed by generation of a transcriptional network model to observe common nodes that functionally couple the two complexes; (3) combine mutations affecting different components of the two complexes into isogenic lines to obtain synthetic phenotypes that provide insights into function and interrelation of the two complexes in vivo; and (4) build a testable logic switch model and develop quantitative markers to test and revise the model. The collaborative approach taken for studying the interactions between quiescence and cell proliferation regulators is aimed at transforming the understanding of the networks that establish and maintain coordinated global responses to metabolic and nutritional cues.