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

单细胞生物，如原生生物和细菌，生活在不稳定的环境中，那里的营养供应并不总是有保证的。为了应对这种“盛宴或饥荒”的不确定性，细胞已经进化出一些过程，使它们能够在营养存在时适当地生长和分裂（增殖），或者在饥饿时进入休眠状态并采取能量保存状态（静止）。该项目利用单细胞参考生物——绿藻衣藻，来研究控制增殖和静止的分子开关是如何被控制的，以及它们是如何协调以确保它们不相互干扰的。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。人们预计，关于控制增殖和静止状态之间转换的分子开关的知识将允许预测如何控制和设计这些状态。因此，新发现的这些分子开关的细节为从饥饿反应中分离高产量的有价值化合物提供了潜在的工程策略。来自两个研究地点的学生和博士后将合作确定和模拟在包括植物和动物在内的许多其他物种中有对应的静止和增殖的关键调节因子之间的相互作用。方法的多样性和定量培训组成部分为受训者在工业或学术界的科学事业做好准备。该项目的长期目标是获得对营养和代谢线索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。在单细胞绿藻莱茵衣藻中，已经确定了两个核蛋白复合物CHT7-C和RB-C，它们控制着营养剥夺诱导的静止、细胞生长和细胞分裂之间的转变。据推测，静止调节因子CHT7-C和细胞周期承诺调节因子RB-C形成了一个互锁的转录网络，协调控制细胞生长和分裂对营养或代谢信号的反应。本项目的目标是：(1)表征纯化的CHT7-C和RB-C配合物，以确定它们的亚基组成和在不同生命周期状态下的修饰；(2)鉴定CHT7-C和RB-C靶基因，建立转录网络模型，观察两个复合物功能偶联的共同节点；(3)将影响两种复合物不同组分的突变组合成等基因系，获得合成表型，从而深入了解两种复合物在体内的功能和相互关系；(4)建立可测试的逻辑开关模型，并开发定量标记对模型进行测试和修正。研究静止和细胞增殖调节因子之间相互作用的合作方法旨在改变对建立和维持对代谢和营养线索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.